Updated on 2023/02/06

写真a

 
INOUE, Akio
 
Scopus Paper Info  
Paper Count: 0  Citation Count: 0  h-index: 28

Citation count denotes the number of citations in papers published for a particular year.

Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor(without tenure)
Mail Address
メールアドレス

Research Institute

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

Education

  • 2000.04
    -
    2003.03

    Kyoto University   Graduate School of Science   Department of Astronomy  

  • 1998.04
    -
    2000.03

    Kyoto University   Graduate School of Science   Department of Astronomy  

  • 1994.04
    -
    1998.03

    Kyoto University   Faculty of Science  

Degree

  • Kyoto University   Doctor of Science

Research Experience

  • 2019.04
    -
    Now

    Waseda University   Faculty of Science and Engineering   Professor (Not tenured)

  • 2017.04
    -
    2019.03

    Osaka Sangyo University   Department of Environmental Science and Technology, Faculty of Design Technology   Associate professor

  • 2008.04
    -
    2017.03

    Osaka Sangyo University, College of General Education, Physics, Associate professor

  • 2005.04
    -
    2008.03

    Osaka Sangyo University, College of General Education, Physics, Assistant professor

Professional Memberships

  •  
     
     

    Astronomical Society of Japan

  •  
     
     

    The Japanese Society for Planetary Sciences

  •  
     
     

    International Astronomical Union

  •  
     
     

    American Astronomical Society

  •  
     
     

    理論天文学宇宙物理学懇談会

  •  
     
     

    光赤外線天文連絡会

▼display all

 

Research Areas

  • Astronomy

Papers

  • GREX-PLUS: galaxy reionization explorer and planetary universe spectrometer

    Akio K. Inoue, Hidehiro Kaneda, Toru Yamada, Yuichi Harikane, Daisuke Ishihara, Tadayuki Kodama, Yutaka Komiyama, Takashi Moriya, Kentaro Motohara, Hideko Nomura, Masami Ouchi, Shinki Oyabu, Toyoaki Suzuki, Takehiko Wada, Issei Yamamura

    Space Telescopes and Instrumentation 2022: Optical, Infrared, and Millimeter Wave    2022.08

    DOI

    Scopus

  • A Search for H-Dropout Lyman Break Galaxies at z ∼ 12–16

    Yuichi Harikane, Akio K. Inoue, Ken Mawatari, Takuya Hashimoto, Satoshi Yamanaka, Yoshinobu Fudamoto, Hiroshi Matsuo, Yoichi Tamura, Pratika Dayal, L. Y. Aaron Yung, Anne Hutter, Fabio Pacucci, Yuma Sugahara, Anton M. Koekemoer

    The Astrophysical Journal   929 ( 1 ) 1 - 1  2022.04

     View Summary

    Abstract

    We present two bright galaxy candidates at z ∼ 12–13 identified in our H-dropout Lyman break selection with 2.3 deg2 near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 μm, a flat continuum at 2–5 μm, and nondetections at <1.2 μm in the available photometric data sets, all of which are consistent with a z > 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4σ [O iii] 88 μm line at z = 13.27, in agreement with its photometric redshift estimate. The number density of the z ∼ 12–13 candidates is comparable to that of bright z ∼ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from z ∼ 4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z ∼ 10–13. Combined with recent studies reporting similarly bright galaxies at z ∼ 9–11 and mature stellar populations at z ∼ 6–9, our results indicate the existence of a number of star-forming galaxies at z > 10, which will be detected with upcoming space missions such as the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.

    DOI

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    11
    Citation
    (Scopus)
  • AstroSat detection of Lyman continuum emission from a z = 1.42 galaxy

    Kanak Saha, Shyam N. Tandon, Charlotte Simmonds, Anne Verhamme, Abhishek Paswan, Daniel Schaerer, Michael Rutkowski, Anshuman Borgohain, Bruce Elmegreen, Akio K. Inoue, Francoise Combes, Debra Elmegreen, Mieke Paalvast

    Nature Astronomy   4 ( 12 ) 1185 - 1194  2020.12

     View Summary

    One of the outstanding problems of current observational cosmology is to understand the nature of sources that produced the bulk of the ionizing radiation after the Cosmic Dark Age. Direct detection of these reionization sources1 is practically infeasible at high redshift (z) due to the steep decline of intergalactic medium transmission2,3. However, a number of low-z analogues emitting Lyman continuum at 900 Å restframe are now detected at z < 0.4 (refs. 4–8) and there are also detections in the range 2.5 < z < 3.5 (refs. 9–14). Here we report the detection of Lyman continuum emission with a high escape fraction (>20%) from a low-mass clumpy galaxy at z = 1.42, in the middle of the redshift range where no detection has been made before and near the peak of the cosmic star-formation history15. The observation was made in the Hubble Extreme Deep Field16 by the wide-field Ultraviolet Imaging Telescope17 onboard AstroSat18. This detection of extreme ultraviolet radiation from a distant galaxy at a restframe wavelength of 600 Å opens up a new window to constrain the shape of the ionization spectrum. Further observations with AstroSat should substantially increase the sample of Lyman-continuum-leaking galaxies at cosmic noon.

    DOI

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    22
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    (Scopus)
  • CHORUS. I. Cosmic HydrOgen reionization unveiled with subaru: Overview

    Akio K. Inoue, Satoshi Yamanaka, Masami Ouchi, Ikuru Iwata, Kazuhiro Shimasaku, Yoshiaki Taniguchi, Tohru Nagao, Nobunari Kashikawa, Yoshiaki Ono, Ken Mawatari, Takatoshi Shibuya, Masao Hayashi, Hiroyuki Ikeda, Haibin Zhang, Yongming Liang, Chien Hsiu Lee, Miftahul Hilmi, Satoshi Kikuta, Haruka Kusakabe, Hisanori Furusawa, Tomoki Hayashino, Masaru Kajisawa, Yuichi Matsuda, Kimihiko Nakajima, Rieko Momose, Yuichi Harikane, Tomoki Saito, Tadayuki Kodama, Shotaro Kikuchihara, Masanori Iye, Tomotsugu Goto

    Publications of the Astronomical Society of Japan   72 ( 6 )  2020.12

     View Summary

    To determine the dominant sources for cosmic reionization, the evolution history of the global ionizing fraction, and the topology of the ionized regions, we have conducted a deep imaging survey using four narrow-band (NB) and one intermediate-band (IB) filters on the Subaru/Hyper Suprime-Cam (HSC), called Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS). The central wavelengths and full-widths-at-half-maximum of the CHORUS filters are, respectively, 386.2 nm and 5.5 nm for NB387, 526.0 nm and 7.9 nm for NB527, 717.1 nm and 11.1 nm for NB718, 946.2 nm and 33.0 nm for IB945, and 971.2 nm and 11.2 nm for NB973. This combination, including NB921 (921.5 nm and 13.5 nm) from the Subaru Strategic Program with HSC (HSC SSP), is carefully designed, as if they were playing a chorus, to observe multiple spectral features simultaneously, such as Lyman continuum, Lyα, C IV, and He II for z = 2-7. The observing field is the same as that of the deepest footprint of the HSC SSP in the COSMOS field and its effective area is about 1.6 deg2. We present an overview of the CHORUS project, which includes descriptions of the filter design philosophy, observations and data reduction, multiband photometric catalogs, assessments of the imaging quality, measurements of the number counts, and example use cases for the data. All the imaging data, photometric catalogs, masked pixel images, data of limiting magnitudes and point spread functions, results of completeness simulations, and source number counts are publicly available through the HSC SSP database.

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    2
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  • Radiative equilibrium estimates of dust temperature and mass in high-redshift galaxies

    Akio K. Inoue, Takuya Hashimoto, Hiroki Chihara, Chiyoe Koike

    Monthly Notices of the Royal Astronomical Society   495 ( 2 ) 1577 - 1592  2020.06

     View Summary

    The estimation of the temperature and mass of dust in high-redshift galaxies is essential for discussions of the origin of dust in the early Universe. However, this is made difficult by limited sampling of the infrared spectral-energy distribution. Here, we present an algorithm for deriving the temperature and mass of dust in a galaxy, assuming dust to be in radiative equilibrium. We formulate the algorithm for three geometries: a thin spherical shell, a homogeneous sphere and a clumpy sphere. We also discuss the effects of the mass absorption coefficients of dust at ultraviolet and infrared wavelengths, κUV and κIR, respectively. As an example, we apply the algorithm to a normal, dusty star-forming galaxy at z = 7.5, A1689zD1, for which three data points in the dust continuum are available. Using κUV = 5.0 × 104 and κIR = 30(λ/100 μm)−β cm2 g−1 with β = 2.0, we obtain dust temperatures of 38–70 K and masses of 106.5–7.3 M☉ for the three geometries considered. We obtain similar temperatures and masses from just a single data point in the dust continuum, suggesting that the algorithm is useful for high-redshift galaxies with limited infrared observations. In the case of the clumpy sphere, the temperature becomes equal to that of the usual modified black-body fit, because an additional parameter describing the clumpiness works as an adjuster. The best-fitting clumpiness parameter is ξcl = 0.1, corresponding to ∼10 per cent of the volume filling factor of the clumps in this high-redshift galaxy if the clump size is ∼10 pc, similar to that of giant molecular clouds in the local Universe.

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    18
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  • Balmer Break Galaxy Candidates at z~6: a Potential View on the Star-Formation Activity at z>14

    Ken Mawatari, Akio K. Inoue, Takuya Hashimoto, John Silverman, Masaru Kajisawa, Satoshi Yamanaka, Toru Yamada, Iary Davidzon, Peter Capak, Lihwai Lin, Bau-Ching Hsieh, Yoshiaki Taniguchi, Masayuki Tanaka, Yoshiaki Ono, Yuichi Harikane, Yuma Sugahara, Seiji Fujimoto, Tohru Nagao

    The Astrophysical Journal   889 ( 2 ) 137  2020  [Refereed]

     View Summary

    We search for galaxies with a strong Balmer break (Balmer break galaxies; BBGs) at z ∼ 6 over a 0.41 deg2 effective area in the COSMOS field. Based on rich imaging data, including data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), three candidates are identified by their extremely red K-[3.6] colors, as well as by nondetection in the X-ray, optical, far-infrared, and radio bands. The nondetection in the deep ALMA observations suggests that they are not dusty galaxies but BBGs at z ∼ 6, although contamination from active galactic nuclei at z ∼ 0 cannot be completely ruled out for the moment. Our spectral energy distribution analyses reveal that the BBG candidates at z ∼ 6 have stellar masses of ≈5 × 1010 M o&dot; dominated by old stellar populations with ages of ⪆ 700 Myr. Assuming that all three candidates are real BBGs at z ∼ 6, we estimate the stellar mass density to be 2.4-1.3 +2.3× 10-4,M Mpc-3. This is consistent with an extrapolation from the lower-redshift measurements. The onset of star formation in the three BBG candidates is expected to be several hundred million yr before the observed epoch of z ∼ 6. We estimate the star formation rate density (SFRD) contributed by progenitors of the BBGs to be 2.4-12 × 10-5 M o&dot; yr-1 Mpc-3 at z > 14 (99.7% confidence range). Our result suggests a smooth evolution of the SFRD beyond z = 8.

    DOI

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    20
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  • Detections of far-infrared [OIII] and dust emission in a galaxy at z = 8.312: Early metal enrichment in the heart of the reionization era

    Y. Tamura, K. Mawatari, T. Hashimoto, A. K. Inoue, E. Zackrissonm, L. Christensen, C. Binggeli, Y. Matsuda, H. Matsuo, T. T. Takeuchi, R. S. Asano, K. Sunaga, I. Shimizu, T. Okamoto, N. Yoshida, M. Lee, T. Shibuya, Y. Taniguchi, H. Umehata, B. Hatsukade, K. Kohno, K. Ota

    Proceedings of the International Astronomical Union   15 ( S341 ) 211 - 215  2019.11

     View Summary

    <title>Abstract</title>We present ALMA detection of the [O <sc>iii</sc>] 88 <italic>μ</italic>m line and 850 <italic>μ</italic>m dust continuum emission in a <italic>Y</italic>-dropout Lyman break galaxy, MACS0416_Y1. The [O <sc>iii</sc>] detection confirms the object with a spectroscopic redshift to be <italic>z</italic> = 8.3118±0.0003. The 850 <italic>μ</italic>m continuum intensity (0.14 mJy) implies a large dust mass on the order of 4×106<italic>M</italic>. The ultraviolet-to-far infrared spectral energy distribution modeling, where the [O <sc>iii</sc>] emissivity model is incorporated, suggests the presence of a young (τage ≍ 4 Myr), star-forming (SFR ≍ 60<italic>M</italic>yr−1), and moderately metal-polluted (<italic>Z</italic> ≍ 0.2<italic>Z</italic>) stellar component with a stellar mass of 3 × 108<italic>M</italic>. An analytic dust mass evolution model with a single episode of star formation does not reproduce the metallicity and dust mass in ≍ 4 Myr, suggesting an underlying evolved stellar component as the origin of the dust mass.

    DOI

  • Enhancement of H I absorption associated with the z = 3.1 large-scale proto-cluster and characteristic structures with AGNs sculptured over Gpc scale in the SSA22 field

    Hayashino T, Inoue A.~K, Kousai K, Kashikawa N, Mawatari K, Matsuda Y, Tejos N, Prochaska J, Iwata I, Noll S, Burgarella D, Yamada T, Akiyama M

    \mnras   484 ( 4 ) 5868 - 5887  2019  [Refereed]

     View Summary

    In the SSA22 field which exhibits a large-scale proto-cluster at z = 3.1, we carried out a spectroscopic survey for Lyman Break Galaxies (LBGs) with the VLT/VIMOS and identified 78 confident LBGs at z = 2.5-4. We stacked their spectra in the observer's frame by using a sophisticated method. Analysing the composite spectrum, we have revealed that the large-scale proto-cluster at z = 3.1 has a strong HI absorption dip of rest-frame equivalent width of - 1.7 angstrom. Another strong absorption dip found at z = 3.28 is associated with a modestly high-density LBG peak, similar to that at z = 3.1. We have also detected an HI transparency peak at z = 2.98 in the composite spectrum, coincident with a void in the LBG distribution. In this paper, we also investigated the relation between LBGs, HI gas, and active galactic nuclei (AGNs) at z = 3-4 in the SSA22 field. Two AGNs at z = 3.353 and 3.801 are, respectively, associated with the LBG concentration of an overdensity factor delta(LBG) similar or equal to 2 in the present statistics. Another structure at z = 3.453 is remarkable: 20 comoving Mpc-scale dense HI gas which is not associated with any apparent LBG overdensity but involving a pair of AGNs. Such structure may be a new type of the AGN-matter correlation. If the inhomogeneous structures over a comoving Gpc scale found in this paper are confirmed with sufficient statistics in the future, the SSA22 field will become a key region to test the standard cold dark matter structure formation scenario.

    DOI

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    6
    Citation
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  • Detection of the Far-infrared [O III] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era

    Yoichi Tamura, Ken Mawatari, Takuya Hashimoto, Akio K. Inoue, Erik Zackrisson, Lise Christensen, Christian Binggeli, Yuichi Matsuda, Hiroshi Matsuo, Tsutomu T. Takeuchi, Ryosuke S. Asano, Kaho Sunaga, Ikkoh Shimizu, Takashi Okamoto, Naoki Yoshida, Minju Lee, Takatoshi Shibuya, Yoshiaki Taniguchi, Hideki Umehata, Bunyo Hatsukade, Kotaro Kohno, Kazuaki Ota

    ASTROPHYSICAL JOURNAL   874 ( 1 )  2018.06  [Refereed]

     View Summary

    We present the Atacama Large Millimeter/submillimeter Array (ALMA) detection
    of the [O III] 88 $\mu$m line and rest-frame 90 $\mu$m dust continuum emission
    in a Y-dropout Lyman break galaxy (LBG), MACS0416_Y1, lying behind the Frontier
    Field cluster MACS J0416.1-2403. This [O III] detection confirms the LBG with a
    spectroscopic redshift of $z = 8.3118 \pm 0.0003$, making this object one of
    the furthest galaxies ever identified spectroscopically. The observed 850
    $\mu$m flux density of $137 \pm 26$ $\mu$Jy corresponds to a de-lensed total
    infrared (IR) luminosity of $L_{\rm IR} = (1.7 \pm 0.3) \times 10^{11}
    L_{\odot}$ if assuming a dust temperature of $T_{\rm dust} = 50$ K and an
    emissivity index of $\beta = 1.5$, yielding a large dust mass of $4 \times 10^6
    M_{\odot}$. The ultraviolet-to-far IR spectral energy distribution modeling
    where the [O III] emissivity model is incorporated suggests the presence of a
    young ($\tau_{\rm age} \approx 4$ Myr), star-forming (SFR $\approx 60
    M_{\odot}$ yr$^{-1}$), moderately metal-polluted ($Z \approx 0.2 Z_{\odot}$)
    stellar component with a mass of $M_{\rm star} = 3 \times 10^8 M_{\odot}$. An
    analytic dust mass evolution model with a single episode of star-formation does
    not reproduce the metallicity and dust mass in $\tau_{\rm age} \approx 4$ Myr,
    suggesting a pre-existing evolved stellar component with $M_{\rm star} \sim 3
    \times 10^9 M_{\odot}$ and $\tau_{\rm age} \sim 0.3$ Gyr as the origin of the
    dust mass.

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    112
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  • "Big Three Dragons": a z = 7.15 Lyman BreakGalaxy Detected in [OIII] 88 $μ$m, [CII] 158 $μ$m, and Dust Continuum with ALMA

    Takuya Hashimoto, Akio K. Inoue, Ken Mawatari, Yoichi Tamura, Hiroshi Matsuo, Hisanori Furusawa, Yuichi Harikane, Takatoshi Shibuya, Kirsten K. Knudsen, Kotaro Kohno, Yoshiaki Ono, Erik Zackrisson, Takashi Okamoto, Nobunari Kashikawa, Pascal A. Oesch, Masami Ouchi, Kazuaki Ota, Ikkoh Shimizu, Yoshiaki Taniguchi, Hideki Umehata, Darach Watson

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   71 ( 4 )  2018.06  [Refereed]

     View Summary

    We present new ALMA observations and physical properties of a Lyman Break
    Galaxy at z=7.15. Our target, B14-65666, has a bright ultra-violet (UV)
    absolute magnitude, $M_{\rm UV}\approx-22.4$, and has been spectroscopically
    identified in Ly$\alpha$ with a small rest-frame equivalent width of $\approx4$
    \AA. Previous HST image has shown that the target is comprised of two spatially
    separated clumps in the rest-frame UV. With ALMA, we have newly detected
    spatially resolved [OIII] 88 $\mu$m, [CII] 158 $\mu$m, and their underlying
    dust continuum emission. In the whole system of B14-65666, the [OIII] and [CII]
    lines have consistent redshifts of $7.1520\pm0.0003$, and the [OIII]
    luminosity, $(34.4\pm4.1)\times10^{8}L_{\rm \odot}$, is about three times
    higher than the [CII] luminosity, $(11.0\pm1.4)\times10^{8}L_{\rm \odot}$. With
    our two continuum flux densities, the dust temperature is constrained to be
    $T_{\rm d}\approx50-60$ K under the assumption of the dust emissivity index of
    $\beta_{\rm d}=2.0-1.5$, leading to a large total infrared luminosity of
    $L_{\rm TIR}\approx1\times10^{12}L_{\rm \odot}$. Owing to our high spatial
    resolution data, we show that the [OIII] and [CII] emission can be spatially
    decomposed into two clumps associated with the two rest-frame UV clumps whose
    spectra are kinematically separated by $\approx200$ km s$^{-1}$. We also find
    these two clumps have comparable UV, infrared, [OIII], and [CII] luminosities.
    Based on these results, we argue that B14-65666 is a starburst galaxy induced
    by a major-merger. The merger interpretation is also supported by the large
    specific star-formation rate (defined as the star-formation rate per unit
    stellar mass), sSFR$=260^{+119}_{-57}$ Gyr$^{-1}$, inferred from our SED
    fitting. Probably, a strong UV radiation field caused by intense star formation
    contributes to its high dust temperature and the [OIII]-to-[CII] luminosity
    ratio.

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    118
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  • SILVERRUSH. VI. A simulation of Lyα emitters in the reionization epoch and a comparison with Subaru Hyper Suprime-Cam survey early data

    Inoue, Akio K, Hasegawa, Kenji, Ishiyama, Tomoaki, Yajima, Hidenobu, Shimizu, Ikkoh, Umemura, Masayuki, Konno, Akira, Harikane, Yuichi, Shibuya, Takatoshi, Ouchi, Masami, Shimasaku, Kazuhiro, Ono, Yoshiaki, Kusakabe, Haruka, Higuchi, Ryo, Lee, Chien-Hsiu

    Publications of the Astronomical Society of Japan   70 ( 3 ) id. 55, 30 pp.  2018.06  [Refereed]

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    41
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  • The onset of star formation 250 million years after the Big Bang

    Takuya Hashimoto, Nicolas Laporte, Ken Mawatari, Richard S. Ellis, Akio. K. Inoue, Erik Zackrisson, Guido Roberts-Borsani, Wei Zheng, Yoichi Tamura, Franz E. Bauer, Thomas Fletcher, Yuichi Harikane, Bunyo Hatsukade, Natsuki H. Hayatsu, Yuichi Matsuda, Hiroshi Matsuo, Takashi Okamoto, Masami Ouchi, Roser Pello, Claes-Erik Rydberg, Ikkoh Shimizu, Yoshiaki Taniguchi, Hideki Umehata, Naoki Yoshida

    Nature   557 ( 7705 ) 392 - 395  2018.05  [Refereed]

     View Summary

    A fundamental quest of modern astronomy is to locate the earliest galaxies
    and study how they influenced the intergalactic medium a few hundred million
    years after the Big Bang. The abundance of star-forming galaxies is known to
    decline from redshifts of about 6 to 10, but a key question is the extent of
    star formation at even earlier times, corresponding to the period when the
    first galaxies might have emerged. Here we present spectroscopic observations
    of MACS1149-JD1, a gravitationally lensed galaxy observed when the Universe was
    less than four per cent of its present age. We detect an emission line of
    doubly ionized oxygen at a redshift of $9.1096\pm0.0006$, with an uncertainty
    of one standard deviation. This precisely determined redshift indicates that
    the red rest-frame optical colour arises from a dominant stellar component that
    formed about 250 million years after the Big Bang, corresponding to a redshift
    of about 15. Our results indicate the it may be possible to detect such early
    episodes of star formation in similar galaxies with future telescopes.

    DOI

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    192
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  • Detection of an oxygen emission line from a high redshift galaxy in the reionization epoch

    Akio K. Inoue, Yoichi Tamura, Hiroshi Matsuo, Ken Mawatari, Ikkoh Shimizu, Takatoshi Shibuya, Kazuaki Ota, Naoki Yoshida, Erik Zackrisson, Nobunari Kashikawa, Kotaro Kohno, Hideki Umehata, Bunyo Hatsukade, Masanori Iye, Yuichi Matsuda, Takashi Okamoto, Yuki Yamaguchi

    Science   352 ( 6293 ) 1559 - 1562  2016.06  [Refereed]

     View Summary

    The physical properties and elemental abundances of the interstellar medium
    in galaxies during cosmic reionization are important for understanding the role
    of galaxies in this process. We report the Atacama Large
    Millimeter/submillimeter Array detection of an oxygen emission line at a
    wavelength of 88 micrometers from a galaxy at an epoch about 700 million years
    after the Big Bang. The oxygen abundance of this galaxy is estimated at about
    one-tenth that of the Sun. The non-detection of far-infrared continuum emission
    indicates a deficiency of interstellar dust in the galaxy. A carbon emission
    line at a wavelength of 158 micrometers is also not detected, implying an
    unusually small amount of neutral gas. These properties might allow ionizing
    photons to escape into the intergalactic medium.

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    143
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  • An updated analytic model for attenuation by the intergalactic medium

    Akio K. Inoue, Ikkoh Shimizu, Ikuru Iwata, Masayuki Tanaka

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   442 ( 2 ) 1805 - 1820  2014.08  [Refereed]

     View Summary

    We present an updated version of the so-called Madau model for attenuation of the radiation from distant objects by intergalactic neutral hydrogen. First, we derive the distribution function of intergalactic absorbers from the latest observational statistics of the Ly alpha forest, Lyman-limit systems and damped Ly alpha systems. The distribution function reproduces the observed redshift evolution of the Ly alpha depression and the mean-free path of the Lyman continuum excellently and simultaneously. We then derive a set of analytic functions describing the mean intergalactic attenuation curve for objects at z &gt; 0.5. The new model predicts less (or more) Ly alpha attenuation for z a parts per thousand integral 3-5 (z &gt; 6) sources through the usual broad-band filters relative to the original Madau model. This may cause a systematic difference in the photometric redshift estimates, which is, however, still small: about 0.05. Finally, we find a more than 0.5 mag overestimation of Lyman-continuum attenuation in the original Madau model at z &gt; 3, which causes a significant overcorrection against direct observations of the Lyman continuum of galaxies.

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    205
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  • ALMA will determine the spectroscopic redshift z>8 with FIR [O III] emission lines

    Akio K. Inoue, Ikkoh Shimizu, Yoichi Tamura, Hiroshi Matsuo, Takashi Okamoto, Naoki Yoshida

    The Astrophysical Journal   780 ( 2 ) article id. L18, 5 pp.  2013.12  [Refereed]

     View Summary

    We investigate the potential use of nebular emission lines in the rest-frame
    far-infrared (FIR) for determining spectroscopic redshift of z>8 galaxies with
    the Atacama Large Millimeter/sub-millimeter Array (ALMA). After making a line
    emissivity model as a function of metallicity, especially for the [O III] 88
    micron line which is likely to be the strongest FIR line from H II regions, we
    predict the line fluxes from high-z galaxies based on a cosmological
    hydrodynamics simulation of galaxy formation. Since the metallicity of galaxies
    reaches at ~0.2 Zsun even at z>8 in our simulation, we expect the [O III] 88
    micron line as strong as 1.3 mJy for 27 AB objects, which is detectable at a
    high significance by <1 hour integration with ALMA. Therefore, the [O III] 88
    micron line would be the best tool to confirm the spectroscopic redshifts
    beyond z=8.

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    34
    Citation
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  • Rest-frame ultraviolet-to-optical spectral characteristics of extremely metal-poor and metal-free galaxies

    Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   415 ( 3 ) 2920 - 2931  2011.08  [Refereed]

     View Summary

    Finding the first generation of galaxies in the early Universe is the greatest step forward towards understanding galaxy formation and evolution. For a strategic survey of such galaxies and the interpretation of the obtained data, this paper presents an ultraviolet-to-optical spectral model of galaxies with a great care of the nebular emission. In particular, we present a machinereadable table of intensities of 119 nebular emission lines from Ly alpha to the rest-frame 1 mu m as a function of metallicity from zero to the solar one. Based on the spectral model, we present criteria of equivalent widths of Ly alpha, He II lambda 1640, H alpha, H beta and [OIII]lambda 5007 to select extremely metal-poor and metal-free galaxies although these criteria have uncertainty caused by the Lyman continuum escape fraction and the star formation duration. We also present criteria of broad-band colours which will be useful to select candidates for spectroscopic follow-up from drop-out galaxies. We propose the line intensity ratio of [OIII]lambda 5007 to H beta &lt; 0.1 as the most robust criterion for &lt; 1/1000 of the solar metallicity. This ratio of a galaxy with a few M(circle dot)yr(-1) at z similar to 8 is detectable by spectroscopy with the James Webb Space Telescope within a reasonable exposure time.

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    163
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  • The origin of dust in galaxies revisited: the mechanism determining dust content

    Akio K. Inoue

    EARTH PLANETS AND SPACE   63 ( 10 ) 1027 - 1039  2011  [Refereed]

     View Summary

    The origin of cosmic dust is a fundamental issue in planetary science. This paper revisits the origin of dust in galaxies, in particular, in the Milky Way, by using a chemical evolution model of a galaxy composed of stars, interstellar medium, metals (elements heavier than helium), and dust. We start from a review of time-evolutionary equations of the four components, and then, we present simple recipes for the stellar remnant mass and yields of metal and dust based on models of stellar nucleosynthesis and dust formation. After calibrating some model parameters with the data from the solar neighborhood, we have confirmed a shortage of the stellar-dust-production rate relative to the dust-destruction rate by supernovae if the destruction efficiency suggested by theoretical works is correct. If the dust-mass growth by material accretion in molecular clouds is active, the observed dust amount in the solar neighborhood is reproduced. We present a clear analytic explanation of the mechanism for determining dust content in galaxies after the activation of accretion growth: a balance between accretion growth and supernova destruction. Thus, the dust content is independent of the uncertainty of the stellar dust yield after the growth activation. The timing of the activation is determined by a critical metal mass fraction which depends on the growth and destruction efficiencies. The solar system formation seems to have occurred well after the activation and plenty of dust would have existed in the proto-solar nebula.

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    57
    Citation
    (Scopus)
  • DETECTION OF WATER ICE GRAINS ON THE SURFACE OF THE CIRCUMSTELLAR DISK AROUND HD 142527

    M. Honda, A. K. Inoue, M. Fukagawa, A. Oka, T. Nakamoto, M. Ishii, H. Terada, N. Takato, H. Kawakita, Y. K. Okamoto, H. Shibai, M. Tamura, T. Kudo, Y. Itoh

    ASTROPHYSICAL JOURNAL LETTERS   690 ( 2 ) L110 - L113  2009.01  [Refereed]

     View Summary

    Coronagraphic imaging for the Herbig Ae star, HD 142527, was performed using the Coronagraphic Imager with Adaptive Optics (CIAO) on the 8.2 m Subaru Telescope. The images were obtained in the H(2)O ice filter (lambda = 3.08 mu m) using adaptive optics (AO), and in the L&apos; band without AO. Combining these data with previous observational results in the H and K bands, we derived the spectra of the scattered light from the circumstellar disk around HD 142527 and detected an H2O ice absorption feature in the spectra. This result can be explained by the presence of silicate and H(2)O ice grains of similar to 1 mu m in size, according to the prediction model by Inoue et al. This grain size is consistent with previous observational study by Fukagawa et al. and Fujiwara et al. The present result demonstrates that high-resolution imaging of disk-scattered light in the ice band is useful for detecting H(2)O ice grain distributions in circumstellar disks.

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    49
    Citation
    (Scopus)
  • The escape fraction of ionizing photons from galaxies at z=0-6

    Akio K. Inoue, Ikuru Iwata, Jean-Michel Deharveng

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   371 ( 1 ) L1 - L5  2006.09  [Refereed]

     View Summary

    The escape fraction of ionizing photons from galaxies is a crucial quantity controlling the cosmic ionizing background radiation and the reionization. Various estimates of this parameter can be obtained in the redshift range z = 0-6, either from direct observations or from the observed ionizing background intensities. We compare them homogeneously in terms of the observed flux density ratio of ionizing (similar to 900 angstrom rest-frame) to non-ionizing ultraviolet (similar to 1500 angstrom rest-frame) corrected for the intergalactic absorption. The escape fraction is found to increase by an order of magnitude, from a value less than 0.01 at z less than or similar to 1 to about 0.1 at z greater than or similar to 4.

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    107
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    (Scopus)
  • Conversion law of infrared luminosity to star-formation rate for galaxies

    AK Inoue, H Hirashita, H Kamaya

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   52 ( 3 ) 539 - 543  2000.06  [Refereed]

     View Summary

    We construct a new algorithm for estimating the star-formation rate (SFR) of galaxies from their infrared (IR) luminosity by developing the theory of the IR emission from a dusty H II region. The derived formula is SFR/(M-circle dot, yr(-1)) = [3.3 x 10(-10)(1 -eta)/(0.4 - 0.2f + 0.6 epsilon)](L-IR(obs)/L-circle dot), where f is the fraction of ionizing photons absorbed by hydrogen, epsilon is the efficiency of dust absorption for nonionizing photons from OB stars, and eta is the cirrus fraction of observed IR luminosity. The previous conversion formulae of SFR from the IR luminosity are applicable to only the case where the observed IR luminosity is nearly equal to the bolometric luminosity (starburst galaxies etc.), except for some empirical formulae. On the other hand, our theoretical SFR is applicable to galaxies even with a moderate star-formation activity. That is, our simple and convenient formula is significantly useful for estimating the SFR of various morphologies and types of galaxies - from early elliptical to late spiral and irregular galaxies, or from active starburst to quiescent galaxies - as long as they have neither an abnormal dust-to-gas ratio nor an evident active galactic nucleus.

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    52
    Citation
    (Scopus)
  • ALMA Observations of CO Emission from Luminous Lyman-break Galaxies at z = 6.0293–6.2037

    Yoshiaki Ono, Seiji Fujimoto, Yuichi Harikane, Masami Ouchi, Livia Vallini, Andrea Ferrara, Takatoshi Shibuya, Andrea Pallottini, Akio K. Inoue, Masatoshi Imanishi, Kazuhiro Shimasaku, Takuya Hashimoto, Chien-Hsiu Lee, Yuma Sugahara, Yoichi Tamura, Kotaro Kohno, Malte Schramm

    The Astrophysical Journal   941 ( 1 ) 74 - 74  2022.12

     View Summary

    Abstract

    We present our new Atacama Large Millimeter/submillimeter Array (ALMA) observations targeting CO(6–5) emission from three luminous Lyman-break galaxies (LBGs) at zspec = 6.0293–6.2037 found in the Subaru/Hyper Suprime-Cam survey, whose [O iii] 88 μm and [C ii] 158 μm emissions have been detected with ALMA. We find a marginal detection of the CO(6–5) line from one of our LBGs, J0235–0532, at the ≃4σ significance level and obtain upper limits for the other two LBGs, J1211–0118 and J0217–0208. Our z = 6 luminous LBGs are consistent with the previously found correlation between the CO luminosity and the infrared luminosity. The unique ensemble of the multiple far-infrared emission lines and underlying continuum fed to a photodissociation region model reveals that J0235–0532 has a relatively high density of hydrogen nuclei nH that is comparable to those of low-z (U)LIRGs, quasars, and Galactic star-forming regions with high nH values, while the other two LBGs have lower nH consistent with local star-forming galaxies. By carefully taking account of various uncertainties, we obtain constraints on total gas mass and gas surface density from their CO luminosity measurements. We find that J0235–0532 is located below the Kennicutt–Schmidt (KS) relation, comparable to the z = 5.7 LBG, HZ10, previously detected with CO(2–1). Combined with previous results for dusty starbursts at similar redshifts, the KS relation at z = 5–6 is on average consistent with the local one.

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  • Bridging Optical and Far-infrared Emission-line Diagrams of Galaxies from Local to the Epoch of Reionization: Characteristic High [O iii] 88 μm/SFR at z &gt; 6

    Yuma Sugahara, Akio K. Inoue, Yoshinobu Fudamoto, Takuya Hashimoto, Yuichi Harikane, Satoshi Yamanaka

    The Astrophysical Journal   935 ( 2 ) 119 - 119  2022.08

     View Summary

    Abstract

    We present photoionization modeling of galaxy populations at z ∼ 0, 2, and &gt;6 to bridge optical and far-infrared (FIR) emission-line diagrams. We collect galaxies with measurements of optical and/or FIR ([O iii] 88 μm and [C ii] 158 μm) emission-line fluxes and plot them on the [O iii]λ5007/Hβ–[N ii]λ6585/Hα (BPT) and L([O iii]88)/SFR–L([C ii]158)/SFR diagrams, where SFR is the star formation rate and L([O iii]88) and L([C ii]158) are the FIR line luminosities. We aim to explain the galaxy distributions on the two diagrams with photoionization models that employ three nebular parameters: the ionization parameter U, hydrogen density nH, and gaseous metallicity Zgas. Our models successfully reproduce the nebular parameters of local galaxies, and then predict the distributions of the z ∼ 0, 2, and &gt;6 galaxies in the diagrams. The predicted distributions illustrate the redshift evolution on all the diagrams; e.g., [O iii]/Hβ and [O iii]88/[C ii]158 ratios continuously decrease from z &gt; 6 to 0. Specifically, the z &gt; 6 galaxies exhibit ∼0.5 dex higher U than low-redshift galaxies at a given Zgas and show predicted flat distributions on the BPT diagram at ${\rm{log } }[{\rm{O } }\,{\rm\small{III } }]/{\rm{H } }\beta \,=\,$ 0.5–0.8. We find that some of the z &gt; 6 galaxies exhibit high L([O iii]88)/SFR ratios. To explain these high ratios, our photoionization models require a low stellar-to-gaseous-metallicity ratio or bursty/increasing star formation history at z &gt; 6. JWST will test the predictions and scenarios for the z &gt; 6 galaxies proposed by our photoionization modeling.

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  • EMPRESS. IV. Extremely Metal-poor Galaxies Including Very Low-mass Primordial Systems with M * = 104–105 M and 2%–3% (O/H): High (Fe/O) Suggestive of Metal Enrichment by Hypernovae/Pair-instability Supernovae

    Yuki Isobe, Masami Ouchi, Akihiro Suzuki, Takashi J. Moriya, Kimihiko Nakajima, Ken’ichi Nomoto, Michael Rauch, Yuichi Harikane, Takashi Kojima, Yoshiaki Ono, Seiji Fujimoto, Akio K. Inoue, Ji Hoon Kim, Yutaka Komiyama, Haruka Kusakabe, Chien-Hsiu Lee, Michael Maseda, Jorryt Matthee, Leo Michel-Dansac, Tohru Nagao, Themiya Nanayakkara, Moka Nishigaki, Masato Onodera, Yuma Sugahara, Yi Xu

    The Astrophysical Journal   925 ( 2 ) 111 - 111  2022.02

     View Summary

    Abstract

    We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H), and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 × 104–7 × 105M and 2%–3% (O/H), respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ∼2% (O/H) show high (Fe/O) ratios of ∼0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ∼ 10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies.

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    8
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    (Scopus)
  • Where's Swimmy?: Mining unique color features buried in galaxies by deep anomaly detection using Subaru Hyper Suprime-Cam data

    Takumi S. Tanaka, Rhythm Shimakawa, Kazuhiro Shimasaku, Yoshiki Toba, Nobunari Kashikawa, Masayuki Tanaka, Akio K. Inoue

    Publications of the Astronomical Society of Japan   74 ( 1 ) 1 - 23  2022.02

     View Summary

    We present the Swimmy (Subaru WIde-field Machine-learning anoMalY) survey program, a deep-learning-based search for unique sources using multicolored (grizy) imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). This program aims to detect unexpected, novel, and rare populations and phenomena, by utilizing the deep imaging data acquired from the wide-field coverage of the HSC-SSP. This article, as the first paper in the Swimmy series, describes an anomaly detection technique to select unique populations as "outliers"from the data-set. The model was tested with known extreme emission-line galaxies (XELGs) and quasars, which consequently confirmed that the proposed method successfully selected ∼60%-70% of the quasars and 60% of the XELGs without labeled training data. In reference to the spectral information of local galaxies at z = 0.05-0.2 obtained from the Sloan Digital Sky Survey, we investigated the physical properties of the selected anomalies and compared them based on the significance of their outlier values. The results revealed that XELGs constitute notable fractions of the most anomalous galaxies, and certain galaxies manifest unique morphological features. In summary, deep anomaly detection is an effective tool that can search rare objects, and, ultimately, unknown unknowns with large data-sets. Further development of the proposed model and selection process can promote the practical applications required to achieve specific scientific goals.

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    4
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    (Scopus)
  • A Morphological Study of Galaxies Hosting Optical Variability-selected AGNs in the COSMOS Field

    Yuxing Zhong, Akio K. Inoue, Satoshi Yamanaka, Toru Yamada

    The Astrophysical Journal   925 ( 2 ) 157 - 157  2022.02

     View Summary

    <title>Abstract</title>
    Morphological studies are crucial to investigate the connections between active galactic nucleus (AGN) activities and the evolution of galaxies. Substantial studies have found that radiative-mode AGNs primarily reside in disk galaxies, questioning the merger-driven mechanism of AGN activities. In this study, through Sérsic profile fitting and nonparametric morphological parameter measurements, we investigated the morphology of host galaxies of 485 optical variability-selected low-luminosity AGNs at <italic>z</italic> ≲ 4.26 in the COSMOS field. We analyzed high-resolution images of the Hubble Space Telescope to measure these morphological parameters. We only successfully measured the morphological parameters for 76 objects and most AGN hosts (∼70%) were visually compact point-like sources. We examined the obtained morphological information as a function of redshift and compared them with literature data. We found that these AGN host galaxies showed no clear morphological preference. However, the merger rate increased with higher host star formation rate and AGN luminosity. Interestingly, we found ongoing star formation consistent with the typical star-forming populations in both elliptical and spiral galaxies, while these two types of galaxies were more symmetric than normal star-forming galaxies. These results suggest that optical variability-selected AGNs have higher probabilities to reside in elliptical galaxies than infrared-selected AGNs, whose host galaxies have a strong disk dominance, and support recent findings that the AGN feedback can enhance star-forming activities in host galaxies.

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  • FOREVER22: galaxy formation in protocluster regions

    Hidenobu Yajima, Makito Abe, Sadegh Khochfar, Kentaro Nagamine, Akio K Inoue, Tadayuki Kodama, Shohei Arata, Claudio Dalla Vecchia, Hajime Fukushima, Takuya Hashimoto, Nobunari Kashikawa, Mariko Kubo, Yuexing Li, Yuichi Matsuda, Ken Mawatari, Masami Ouchi, Hideki Umehata

    Monthly Notices of the Royal Astronomical Society   509 ( 3 ) 4037 - 4057  2021.12

     View Summary

    <title>ABSTRACT</title>
    We present results from a new cosmological hydrodynamics simulation campaign of protocluster (PC) regions, FOREVER22: FORmation and EVolution of galaxies in Extremely overdense Regions motivated by SSA22. The simulations cover a wide range of cosmological scales using three different zoom set-ups in a parent volume of $(714.2~\rm cMpc)^{3}$: PCR (Proto-Cluster Region; V = (28.6 cMpc)3, SPH particle mass, mSPH = 4.1 × 106 M⊙, and final redshift, zend = 2.0), BCG (Brightest proto-Cluster Galaxy; V ∼ (10 cMpc)3, mSPH = 5.0 × 105 M⊙ and zend = 4.0), and First (V ∼ (3 cMpc)3, mSPH = 7.9 × 103 M⊙ and zend = 9.5) runs, that allow us to focus on different aspects of galaxy formation. In the PCR runs, we follow 10 PCs, each harbouring 1–4 SMBHs with ${\rm M_{\rm BH } }\ge 10^{9}~{\rm M_{\odot } }$. One of the PC cores shows a spatially close arrangement of seven starburst galaxies with ${\rm SFR} \gtrsim 100~{\rm {\rm M_{\odot } }~{\rm yr^{-1 } } }$ each, that are dust-obscured and would appear as submillimetre galaxies with flux ≳1 mJy at $1.1~ \rm mm$ in observations. The BCG runs show that the total SFRs of haloes hosting BCGs are affected by AGN feedback, but exceed $1000~{\rm {\rm M_{\odot } }~{\rm yr^{-1 } } }$ at z ≲ 6. The First runs resolve mini-haloes hosting population (Pop) III stars and we show that, in PC regions, the dominant stellar population changes from Pop III to Pop II at z ≳ 20, and the first galaxies with ${\rm SFR} \gtrsim 18~{\rm {\rm M_{\odot } }~{\rm yr^{-1 } } }$ form at z ∼ 10. These can be prime targets for future observations with the James Webb Space Telescope. Our simulations successfully reproduce the global star formation activities in observed PCs and suggest that PCs can kickstart cosmic reionization.

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    2
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    (Scopus)
  • Subaru/FOCAS IFU revealed the metallicity gradient of a local extremely metal-poor galaxy

    Yuri Kashiwagi, Akio K Inoue, Yuki Isobe, Kimihiko Nakajima, Masami Ouchi, Shinobu Ozaki, Seiji Fujimoto, Yoshiaki Ono, Takashi Kojima

    Publications of the Astronomical Society of Japan    2021.12  [Refereed]

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  • Big Three Dragons: A [N ii] 122 μm Constraint and New Dust-continuum Detection of a z = 7.15 Bright Lyman-break Galaxy with ALMA

    Yuma Sugahara, Akio K. Inoue, Takuya Hashimoto, Satoshi Yamanaka, Seiji Fujimoto, Yoichi Tamura, Hiroshi Matsuo, Christian Binggeli, Erik Zackrisson

    The Astrophysical Journal   923 ( 1 ) 5 - 5  2021.12

     View Summary

    <title>Abstract</title>
    We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at <italic>z</italic> = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O <sc>iii</sc>] 88 <italic>μ</italic>m, [C <sc>ii</sc>] 158 <italic>μ</italic>m, and dust continuum emission during the epoch of reionization. Our targets are the [N <sc>ii</sc>] 122 <italic>μ</italic>m fine-structure emission line and the underlying 120 <italic>μ</italic>m dust continuum. The dust continuum is detected with a ∼19<italic>σ</italic> significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 <italic>μ</italic>m, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of <inline-formula>
    <tex-math>
    <?CDATA ${\mathrm{log } }_{10}({L}_{\mathrm{IR } }/{L}_{\odot })=11.6$?>
    </tex-math>
    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
    <mml:msub>
    <mml:mrow>
    <mml:mi>log</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mn>10</mml:mn>
    </mml:mrow>
    </mml:msub>
    <mml:mo stretchy="false">(</mml:mo>
    <mml:msub>
    <mml:mrow>
    <mml:mi>L</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mi>IR</mml:mi>
    </mml:mrow>
    </mml:msub>
    <mml:mrow>
    <mml:mo stretchy="true">/</mml:mo>
    </mml:mrow>
    <mml:msub>
    <mml:mrow>
    <mml:mi>L</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mo>⊙</mml:mo>
    </mml:mrow>
    </mml:msub>
    <mml:mo stretchy="false">)</mml:mo>
    <mml:mo>=</mml:mo>
    <mml:mn>11.6</mml:mn>
    </mml:math>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn1.gif" xlink:type="simple" />
    </inline-formula> (12.1) at the emissivity index <italic>β</italic> = 2.0 (1.0). The [N <sc>ii</sc>] 122 <italic>μ</italic>m line is not detected. The 3<italic>σ</italic> upper limit of the [N <sc>ii</sc>] luminosity is 8.1 × 107
    <italic>L</italic>
    . From the [N <sc>ii</sc>], [O <sc>iii</sc>], and [C <sc>ii</sc>] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (<italic>Z</italic> &gt; 0.4 <italic>Z</italic>
    ), the ionization parameter and hydrogen density are <inline-formula>
    <tex-math>
    <?CDATA ${\mathrm{log } }_{10}U\simeq -2.7\pm 0.1$?>
    </tex-math>
    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
    <mml:msub>
    <mml:mrow>
    <mml:mi>log</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mn>10</mml:mn>
    </mml:mrow>
    </mml:msub>
    <mml:mi>U</mml:mi>
    <mml:mo>≃</mml:mo>
    <mml:mo>−</mml:mo>
    <mml:mn>2.7</mml:mn>
    <mml:mo>±</mml:mo>
    <mml:mn>0.1</mml:mn>
    </mml:math>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn2.gif" xlink:type="simple" />
    </inline-formula> and <italic>n</italic>
    H ≃ 50–250 cm−3, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At <italic>Z</italic> &lt; 0.4 <italic>Z</italic>
    , the allowed <italic>U</italic> drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

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  • SILVERRUSH. XI. Constraints on the Lyα Luminosity Function and Cosmic Reionization at z = 7.3 with Subaru/Hyper Suprime-Cam

    Hinako Goto, Kazuhiro Shimasaku, Satoshi Yamanaka, Rieko Momose, Makoto Ando, Yuichi Harikane, Takuya Hashimoto, Akio K. Inoue, Masami Ouchi

    The Astrophysical Journal   923 ( 2 ) 229 - 229  2021.12

     View Summary

    <title>Abstract</title>
    The Ly<italic>α</italic> luminosity function (LF) of Ly<italic>α</italic> emitters (LAEs) has been used to constrain the neutral hydrogen fraction in the intergalactic medium (IGM) and thus the timeline of cosmic reionization. Here we present the results of a new narrowband imaging survey for <italic>z</italic> = 7.3 LAEs in a large area of ∼3 deg2 with Subaru/Hyper Suprime-Cam. No LAEs are detected down to <italic>L</italic>
    <sub>Ly<italic>α</italic>
    </sub> ≃ 1043.2 erg s−1 in an effective cosmic volume of ∼2 × 106 Mpc3, placing an upper limit on the bright part of the <italic>z</italic> = 7.3 Ly<italic>α</italic> LF for the first time and confirming a decrease in bright LAEs from <italic>z</italic> = 7.0. By comparing this upper limit with the Ly<italic>α</italic> LF in the case of fully ionized IGM, which is predicted using an observed <italic>z</italic> = 5.7 Ly<italic>α</italic> LF on the assumption that the intrinsic Ly<italic>α</italic> LF evolves in the same way as the UV LF, we obtain the relative IGM transmission <inline-formula>
    <tex-math>
    <?CDATA ${T}_{\mathrm{Ly}\alpha }^{\mathrm{IGM } }(7.3)/{T}_{\mathrm{Ly}\alpha }^{\mathrm{IGM } }(5.7)\lt 0.77$?>
    </tex-math>
    <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
    <mml:msubsup>
    <mml:mrow>
    <mml:mi>T</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mi>Ly</mml:mi>
    <mml:mi>α</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mi>IGM</mml:mi>
    </mml:mrow>
    </mml:msubsup>
    <mml:mo stretchy="false">(</mml:mo>
    <mml:mn>7.3</mml:mn>
    <mml:mo stretchy="false">)</mml:mo>
    <mml:mrow>
    <mml:mo stretchy="true">/</mml:mo>
    </mml:mrow>
    <mml:msubsup>
    <mml:mrow>
    <mml:mi>T</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mi>Ly</mml:mi>
    <mml:mi>α</mml:mi>
    </mml:mrow>
    <mml:mrow>
    <mml:mi>IGM</mml:mi>
    </mml:mrow>
    </mml:msubsup>
    <mml:mo stretchy="false">(</mml:mo>
    <mml:mn>5.7</mml:mn>
    <mml:mo stretchy="false">)</mml:mo>
    <mml:mo>&lt;</mml:mo>
    <mml:mn>0.77</mml:mn>
    </mml:math>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac308bieqn1.gif" xlink:type="simple" />
    </inline-formula> and then the volume-averaged neutral fraction <italic>x</italic>
    H I(7.3) &gt; 0.28. Cosmic reionization is thus still ongoing at <italic>z</italic> = 7.3, consistent with results from other <italic>x</italic>
    H I estimation methods. A similar analysis using literature Ly<italic>α</italic> LFs finds that at <italic>z</italic> = 6.6 and 7.0, the observed Ly<italic>α</italic> LF agrees with the predicted one, consistent with full ionization.

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    6
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  • Ionizing radiation from AGNs at z &gt; 3.3 with the Subaru Hyper Suprime-Cam Survey and the CFHT Large Area U-band Deep Survey (CLAUDS)

    Ikuru Iwata, Marcin Sawicki, Akio K Inoue, Masayuki Akiyama, Genoveva Micheva, Toshihiro Kawaguchi, Nobunari Kashikawa, Stephen Gwyn, Stephane Arnouts, Jean Coupon, Guillaume Desprez

    Monthly Notices of the Royal Astronomical Society    2021.09

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    5
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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XIII. Large-scale Feedback and Star Formation in a Low-luminosity Quasar at z = 7.07 on the Local Black Hole to Host Mass Relation

    Takuma Izumi, Yoshiki Matsuoka, Seiji Fujimoto, Masafusa Onoue, Michael A. Strauss, Hideki Umehata, Masatoshi Imanishi, Kotaro Kohno, Toshihiro Kawaguchi, Taiki Kawamuro, Shunsuke Baba, Tohru Nagao, Yoshiki Toba, Kohei Inayoshi, John D. Silverman, Akio K. Inoue, Soh Ikarashi, Kazushi Iwasawa, Nobunari Kashikawa, Takuya Hashimoto, Kouichiro Nakanishi, Yoshihiro Ueda, Malte Schramm, Chien-Hsiu Lee, Hyewon Suh

    The Astrophysical Journal   914 ( 1 ) 36 - 36  2021.06

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  • SILVERRUSH X: Machine Learning-aided Selection of 9318 LAEs at z = 2.2, 3.3, 4.9, 5.7, 6.6, and 7.0 from the HSC SSP and CHORUS Survey Data

    Yoshiaki Ono, Ryohei Itoh, Takatoshi Shibuya, Masami Ouchi, Yuichi Harikane, Satoshi Yamanaka, Akio K. Inoue, Toshiyuki Amagasa, Daichi Miura, Maiki Okura, Kazuhiro Shimasaku, Ikuru Iwata, Yoshiaki Taniguchi, Seiji Fujimoto, Masanori Iye, Anton T. Jaelani, Nobunari Kashikawa, Shotaro Kikuchihara, Satoshi Kikuta, Masakazu A. R. Kobayashi, Haruka Kusakabe, Chien-Hsiu Lee, Yongming Liang, Yoshiki Matsuoka, Rieko Momose, Tohru Nagao, Kimihiko Nakajima, Ken-ichi Tadaki

    The Astrophysical Journal   911 ( 2 ) 78 - 78  2021.04

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  • Scattering Polarization of 3 mu m Water-ice Feature by Large Icy Grains

    Ryo Tazaki, Koji Murakawa, Takayuki Muto, Mitsuhiko Honda, Akio K. Inoue

    ASTROPHYSICAL JOURNAL   910 ( 1 )  2021.03

     View Summary

    Water ice has a strong spectral feature at a wavelength of approximately 3 mu m, which plays a vital role in our understanding of the icy universe. In this study, we investigate the scattering polarization of this water-ice feature. The linear polarization degree of light scattered by micron-sized icy grains is known to be enhanced at the ice band; however, the dependence of this polarization enhancement on various grain properties is unclear. We find that the enhanced polarization at the ice band is sensitive to the presence of micron-sized grains as well as their ice abundance. We demonstrate that this enhancement is caused by the high absorbency of the water-ice feature, which attenuates internal scattering and renders the surface reflection dominant over internal scattering. Additionally, we compare our models with polarimetric observations of the low-mass protostar L1551 IRS 5. Our results show that scattering by a maximum grain radius of a few microns with a low water-ice abundance is consistent with observations. Thus, scattering polarization of the water-ice feature is a useful tool for characterizing ice properties in various astronomical environments.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XII. Extended [C ii] Structure (Merger or Outflow) in a z = 6.72 Red Quasar

    Takuma Izumi, Masafusa Onoue, Yoshiki Matsuoka, Michael A. Strauss, Seiji Fujimoto, Hideki Umehata, Masatoshi Imanishi, Taiki Kawamuro, Tohru Nagao, Yoshiki Toba, Kotaro Kohno, Nobunari Kashikawa, Kohei Inayoshi, Toshihiro Kawaguchi, Kazushi Iwasawa, Akio K. Inoue, Tomotsugu Goto, Shunsuke Baba, Malte Schramm, Hyewon Suh, Yuichi Harikane, Yoshihiro Ueda, John D. Silverman, Takuya Hashimoto, Yasuhiro Hashimoto, Soh Ikarashi, Daisuke Iono, Chien Hsiu Lee, Kianhong Lee, Takeo Minezaki, Kouichiro Nakanishi, Suzuka Nakano, Yoichi Tamura, Ji Jia Tang

    Astrophysical Journal   908 ( 2 )  2021.02

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    We present Atacama Large Millimeter/submillimeter Array [C ii] 158 μm line and far-infrared (FIR) continuum emission observations toward HSC J120505.09-000027.9 (J1205-0000) at z = 6.72 with a beam size of ∼0.″8 × 0.″5 (or 4.1 kpc × 2.6 kpc), the most distant red quasar known to date. Red quasars are modestly reddened by dust and are thought to be in rapid transition from an obscured starburst to an unobscured normal quasar, driven by powerful active galactic nucleus (AGN) feedback that blows out a cocoon of interstellar medium. The FIR continuum of J1205-0000 is bright, with an estimated luminosity of L FIR ∼ 3 × 1012 L o˙. The [C ii] line emission is extended on scales of r ∼ 5 kpc, greater than that of the FIR continuum. The line profiles at the extended regions are complex and broad (FWHM ∼ 630-780 km s-1). Although it is not practical to identify the nature of this extended structure, possible explanations include (i) companion/merging galaxies and (ii) massive AGN-driven outflows. For the case of (i), the companions are modestly star-forming (∼10 M o˙ yr-1) but are not detected by our Subaru optical observations (y AB,5σ = 24.4 mag). For the case of (ii), our lower limit to the cold neutral outflow rate is ∼100 M o˙ yr-1. The outflow kinetic energy and momentum are both much lower than predicted in energy-conserving wind models, suggesting that the AGN feedback in this quasar is not capable of completely suppressing its star formation.

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  • A puzzling non-detection of [O III] and [C II] from a z ≈ 7.7 galaxy observed with ALMA

    C. Binggeli, A. K. Inoue, T. Hashimoto, M. C. Toribio, E. Zackrisson, S. Ramstedt, K. Mawatari, Y. Harikane, H. Matsuo, T. Okamoto, K. Ota, I. Shimizu, Y. Tamura, Y. Taniguchi, H. Umehata

    Astronomy and Astrophysics   646  2021.02

     View Summary

    Context. Characterizing the galaxy population in the early Universe holds the key to understanding the evolution of these objects and the role they played in cosmic reionization. However, there have been very few observations at the very highest redshifts to date. Aims. In order to shed light on the properties of galaxies in the high-redshift Universe and their interstellar media, we observe the Lyman-α emitting galaxy z7_GSD_3811 at z = 7.664 with bands 6 and 8 at the Atacama Large Millimeter/submillimeter Array (ALMA). Methods. We target the far-infrared [O iii] 88 µm and [C ii] 158 µm emission lines and dust continuum in the star-forming galaxy z7_GSD_3811 with ALMA. We combine these measurements with earlier observations in the rest-frame ultraviolet (UV) in order to characterize the object and compare the results to those of earlier studies that observed [O iii] and [C ii] emission in high-redshift galaxies. Results. The [O iii] 88 µm and [C ii] 158 µm emission lines are undetected at the position of z7_GSD_3811, with 3σ upper limits of 1.6 × 108 L and 4.0 × 107 L, respectively. We do not detect any dust continuum in band 6 nor band 8. The measured rms in the band 8 and band 6 continua are 26 and 9.9 µJy beam−1, respectively. Similar to several other high-redshift galaxies, z7_GSD_3811 exhibits low [C ii] emission for its star formation rate compared to local galaxies. Furthermore, our upper limit on the [O iii] line luminosity is lower than the previously observed [O iii] lines in high-redshift galaxies with similar UV luminosities. Our ALMA band 6 and 8 dust continuum observations imply that z7_GSD_3811 likely has a low dust content, and our non-detections of the [O iii] and [C ii] lines could indicate that z7_GSD_3811 has a low metallicity (Z. 0.1 Z).

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  • The Spectral Evolution of the First Galaxies. III. Simulated James Webb Space Telescope Spectra of Reionization-epoch Galaxies with Lyman-continuum Leakage (vol 836, 78, 2017)

    Erik Zackrisson, Christian Binggeli, Kristian Finlator, Nickolay Y. Gnedin, Jan-Pieter Paardekooper, Ikkoh Shimizu, Akio K. Inoue, Hannes Jensen, Genoveva Micheva, Sadegh Khochfar, Claudio Dalla Vecchia

    ASTROPHYSICAL JOURNAL   908 ( 1 )  2021.02

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    Due to a mistake, the BPASS v2.0 binary-star model (Stanway et al. 2016) used in Figure 6(b) of the published article featured a different initial mass function (IMF) than the Geneva single-star model used for comparison. While the Geneva model used the Kroupa universal IMF (Kroupa 2001) with upper slope α = 2.3 (dN dM ∝ M-α) at 0.5 ≤ M(M⊙) ≤ 100, the BPASS model used a slope of α = 2.0 throughout the same mass interval. Hence, in its original form, that figure actually illustrated the combined effect of assuming binary stars and adopting a more extreme IMF. This resulted in a greater number of massive stars and a boosted ionizing flux for the BPASS model. In the revised Figure 6(b), we show the corrected comparison with identical IMF slopes (α = 2.3). In this case, the shift between the two sets of simulated galaxies in the EW(Hβ)-β diagram is more modest than in the published article. The galaxies simulated using the BPASS binary-star model are shifted by an average Δ(EW(Hβ)) ≈ 0.2 compared to galaxies simulated using the Geneva single-star model. The difference in UV slope β between the two sets of simulated galaxies is also smaller in the corrected version (Δ(β) < 0.1 on average). The risk of misclassifying high-fesc objects due using a stellar evolutionary model not representative of z > 7 galaxies is therefore somewhat smaller than indicated in the published article. (Figure Presented).

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  • Large format imaging spectrograph for the Large Submillimeter Telescope (LST)

    Kotaro Kohno, Ryohei Kawabe, Yoichi Tamura, Akira Endo, Jochem J. A. Baselmans, Kenichi Karatsu, Akio Inoue, Kana Moriwaki, Natsuki H. Hayatsu, Naoki Yoshida, Yuki Yoshimura, Bunyo Hatsukade, Hideki Umehata, Tai Oshima, Tatsuya Takekoshi, Akio Taniguchi, Pamela Klaassen, Tony Mroczkowski, Claudia Cicone, Frank Bertoldi, Helmut Dannerbauer, Tomoka Tosaki

    Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X    2020.12

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  • Spatially Resolved CIII] λ1909 Emission in Haro 11

    Genoveva Micheva, Göran Östlin, Jens Melinder, Matthew Hayes, M. S. Oey, Akio K. Inoue, Ikuru Iwata, Angela Adamo, Lutz Wisotzki, Kimihiko Nakajima

    Astrophysical Journal   903 ( 2 )  2020.11

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    The C III] 1909 (hereafter C III]) line is the strongest ultraviolet emission line after Lyα and is therefore of interest to high-redshift studies of star-forming (SF) galaxies near the epoch of reionization. It is thought that C III] emission is strongest in galaxies with subsolar metallicity and low mass; however, spectral observations of numerous such galaxies at high and low redshift produce inconclusive or even contradictory results. We present the first-ever C III] imaging, obtained with HST/STIS for the low-redshift SF galaxy Haro 11. Cluster parameters like stellar mass, dust fraction and attenuation, and ionization parameter, obtained through spectral energy distribution fitting, show no correlation with the C III] equivalent width (EW), which may be due to a combination of the limitation of the models and the age homogeneity of the cluster population. Comparing the ratio of C III] emission line flux from individual clusters to that of Hα, [O III], and [O II], we find that the clusters with the highest EW(C III]) can be reconciled only with Cloudy models with an extremely high C/O ratio of 1.4(C/O)e for an ionizing population of single stars, binary stars, or a mixture of binary stars and active galactic nuclei. Given the pointlike nature of strong C III], the integrated total strength of EW(C III]) becomes dependent on the morphology of the galaxy, which would explain the large scatter in EW(C III]) strengths observed in galaxies with otherwise similar SF properties and of similarly low metallicity and stellar mass.

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  • Testing an indirect method for identifying galaxies with high levels of Lyman continuum leakage

    Satoshi Yamanaka, Akio K. Inoue, Toru Yamada, Erik Zackrisson, Ikuru Iwata, Genoveva Micheva, Ken Mawatari, Takuya Hashimoto, Mariko Kubo

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   498 ( 3 ) 3095 - 3114  2020.11

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    Using a sample of galaxies at z approximate to 3 with detected Lyman Continuum (LyC) leakage in the SSA22 field, we attempt to verify a proposed indirect method for identifying cases with high LyC escape fraction f(esc) based on measurements of the H beta equivalent width (EW) and the beta slope of the UV continuum. To this end, we present Keck/MOSFIRE H beta emission line flux measurements of LyC galaxies (LCGs) at spectroscopic redshifts z(spec) similar to 3.3, Lyman break galaxies (LBGs) at photometric redshifts z(phot) = 2.7-3.7, and Ly alpha emitters at z(phot) = 3.1. We also reconfirm the spectroscopic redshifts and measure the H beta emission-line fluxes from two LCGs and six LBGs. For the LCG in our sample with the most extreme f(esc), as revealed by the direct detection of LyC photons, we find that the EW(H beta)-beta method gives a broadly consistent estimate for f(esc), although the error bars remain very large. We also discuss how a combination of f(esc) measurements based on direct and indirect methods can shed light on the LyC escape mechanism and the anisotropy of the leakage.

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  • A 16 deg2 survey of emission-line galaxies at z &lt; 1.6 from HSC-SSP PDR2 and CHORUS

    Masao HAYASHI, Rhythm SHIMAKAWA, Masayuki TANAKA, Masato ONODERA, Yusei KOYAMA, Akio K. INOUE, Yutaka KOMIYAMA, Chien Hsiu LEE, Yen Ting LIN, Kiyoto YABE

    Publications of the Astronomical Society of Japan   72 ( 5 )  2020.10

     View Summary

    We have conducted a comprehensive survey of emission-line galaxies at z 1.6 based on narrow-band (NB) imaging data taken with Hyper Suprime-Cam (HSC) on the Subaru telescope. In this paper, we update the catalogs of Hα, [OIII], and [OII] emission-line galaxies using the data from the second Public Data Release (PDR2) of the Subaru Strategic Program (SSP) of the HSC and Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS) survey along with the spectroscopic redshifts for 2019 emission-line galaxies selected with the PDR1 data. The wider effective coverage of NB816 and NB921, 16.3 deg2 and 16.9 deg2, respectively, are available in the Deep and UltraDeep layers of HSC-SSP from the PDR2. The CHORUS survey provides us with data with additional three NBs (NB527, NB718, and NB973) in the COSMOS field in the UltraDeep layer (1.37 deg2). The five NB datasets allow us to investigate the star-forming galaxies presenting emissionlines at 14 specific redshifts ranging from z ∼ 1.6 down to z ∼ 0.05. We revisit the distribution of large-scale structures and luminosity functions (LFs) for the emission-line galaxies with the large samples of 75377 emission-line galaxies selected. The redshift revolution of LFs shows that the star formation rate densities (SFRDs) decreases monotonically from z ∼ 1.6, which is consistent with the cosmic SFRD known to-date. Our samples of emission-line galaxies covering a sufficiently large survey volume are useful to investigate the evolution of star-forming galaxies since the cosmic noon in a wide range of environments including galaxy clusters, filaments, and voids.

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  • The Lyman Continuum Escape Fraction of Galaxies and AGN in the GOODS Fields

    Brent M. Smith, Rogier A. Windhorst, Seth H. Cohen, Anton M. Koekemoer, Rolf A. Jansen, Cameron White, Sanchayeeta Borthakur, Nimish Hathi, Linhua Jiang, Michael Rutkowski, Russell E. Ryan, Akio K. Inoue, Robert W. O'Connell, John W. MacKenty, Christopher J. Conselice, Joseph Silk

    ASTROPHYSICAL JOURNAL   897 ( 1 )  2020.07

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    We present our analysis of the Lyman continuum (LyC) emission and escape fraction of 111 spectroscopically verified galaxies with and without active galactic nuclei (AGN) from 2.26 < z < 4.3. We extended our ERS sample from Smith et al. with 64 galaxies in the GOODS North and South fields using WFC3/UVIS F225W, F275W, and F336W mosaics we independently drizzled using the HDUV, CANDELS, and UVUDF data. Among the 17 AGN from the 111 galaxies, one provided a LyC detection in F275W at m(AB) = 23.19 mag (signal-to-noise ratio, S/N, similar or equal to 133) and GALEX NUV at mAB = 23.77 mag (S/N similar or equal to 13). We simultaneously fit SDSS and Chandra spectra of this AGN to an accretion disk and Comptonization model, and find f(esc) values of f(esc)(F275W) similar or equal to 28(-4)(+20)% and f(esc)(NUV) similar or equal to 30(-5)(+22)%. For the remaining 110 galaxies, we stack image cutouts that capture their 3 LyC emission using the F225W, F275W, and F336W data of the GOODS and ERS samples, and both combined, as well as subsamples of galaxies with and without AGN, and all galaxies. We find the stack of 17 AGN dominate the LyC production from < z > similar or equal to 2.3-4.3 by a factor of similar to 10 compared to all 94 galaxies without AGN. While the IGM of the early universe may have been reionized mostly by massive stars, there is evidence that a significant portion of the ionizing energy came from AGN.

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  • Large Population of ALMA Galaxies at z &gt; 6 with Very High [O III] 88 μm to [C II] 158 μm Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?

    Harikane, Yuichi, Ouchi, Masami, Inoue, Akio K., Matsuoka, Yoshiki, Tamura, Yoichi, Bakx, Tom, Fujimoto, Seiji, Moriwaki, Kana, Ono, Yoshiaki, Nagao, Tohru, Tadaki, Ken-ichi, Kojima, Takashi, Shibuya, Takatoshi, Egami, Eiichi, Ferrara, Andrea, Gallerani, Simona, Hashimoto, Takuya, Kohno, Kotaro, Matsuda, Yuichi, Matsuo, Hiroshi, Pallottini, Andrea, Sugahara, Yuma, Vallini, Livia

    The Astrophysical Journal   896 ( 2 ) 93 - 93  2020.06  [Refereed]

     View Summary

    We present our new Atacama Large Millimeter/Submillimeter Array (ALMA) observations targeting [O III]88 μm, [C II]158 μm, [N II]122 μm, and dust-continuum emission for three Lyman break galaxies at z = 6.0293-6.2037, identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [O III] and [C II] lines from all of the galaxies at 4.3-11.8σ levels, and identify multi-band dust-continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z &gt; 6, we confirm that all the nine z = 6-9 galaxies have high [O III]/[C II] ratios of ${L}_{[{\rm{O } }{\rm{III } }]}/{L}_{[{\rm{C } }{\rm{II } }]}\sim 3\mbox{--}20$, ∼10 times higher than z ∼ 0 galaxies. We also find a positive correlation between the [O III]/[C II] ratio and the Lyα equivalent width (EW) at the ∼90% significance level. We carefully investigate physical origins of the high [O III]/[C II] ratios at z = 6-9 using Cloudy, and find that high density of the interstellar medium, low C/O abundance ratio, and the cosmic microwave background attenuation are responsible to only a part of the z = 6-9 galaxies. Instead, the observed high [O III]/[C II] ratios are explained by 10-100 times higher ionization parameters or low photodissociation region (PDR) covering fractions of 0%-10%, both of which are consistent with our [N II] observations. The latter scenario can be reproduced with a density-bounded nebula with PDR deficit, which would enhance the Lyα, Lyman continuum, and ${ { \rm{C } } }^{+}$ ionizing photons escape from galaxies, consistent with the [O III]/[C II]-Lyα EW correlation we find....

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  • Outside the Lyman-break box: Detecting Lyman continuum emitters at 3.5 &lt; z &lt; 5.1 with CLAUDS

    U. Meštrić, E. V. Ryan-Weber, J. Cooke, R. Bassett, M. Sawicki, A. L. Faisst, K. Kakiichi, A. K. Inoue, M. Rafelski, L. J. Prichard, S. Arnouts, T. Moutard, J. Coupon, A. Golob, S. Gwyn

    Monthly Notices of the Royal Astronomical Society   494 ( 4 ) 4986 - 5007  2020.06

     View Summary

    Identifying non-contaminated sample of high-redshift galaxies with escaping Lyman continuum (LyC) flux is important for understanding the sources and evolution of cosmic reionization. We present CLAUDS (CFHT Large Area u-band deep survey) u-band photometry of the COSMOS field to probe LyC radiation from spectroscopically confirmed galaxies at z ≥ 3.5 and outside the standard Lyman-break galaxy colour-selection expectations. Complementary to the CLAUDS data, we use Subaru multifilter photometry, Hubble Space Telescope (HST) multifilter imaging, and the spectroscopic surveys D10K, VUDS, and 3D-HST. We present a sample of Lyman continuum galaxy (LCG) candidates in the redshift range 3.5 ≥ z ≥ 5.1. Here, we introduce 5 LCG candidates, where two are flagged quality 1 and three quality 2. The estimated fabsesc for quality 1 candidates are in the range 5 - 73 per cent and 30 - 93 per cent . These estimates are based on our derived parameters from individual galaxies as inputs to a range of BPASS models as well as mean intergalactic medium (IGM) and maximal intergalactic and circumgalactic media (IGM+CGM) transmission. We conclude that our search for LCGs is most likely biased to lines of sight with low H i densities or free from Lyman limit systems. Our two best LCG candidates have EW (Lyα) ≤ 50 Å and we find no correlation or anticorrelation between EW (Lyα), fabsesc, and Robs, the ratio of ionizing to non-ionizing observed flux in the measured passbands. Stacking candidates without solid LyC detections (S/N < 3) results in an estimated fabsesc from galaxies not greater than 1 per cent.

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  • Observational and theoretical constraints on the formation and early evolution of the first dust grains in galaxies at 5 &lt; z &lt; 10

    D. Burgarella, A. Nanni, H. Hirashita, P. Theulé, A. K. Inoue, T. T. Takeuchi

    Astronomy and Astrophysics   637  2020.05

     View Summary

    Context. The first generation of stars were born a few hundred million years after the big bang. These stars synthesise elements heavier than H and He, which are later expelled into the interstellar medium, initiating the rise of metals. Within this enriched medium, the first dust grains were formed. This event is cosmologically crucial for molecule formation, as dust plays a major role by cooling low-metallicity star-forming clouds, which can fragment to create lower mass stars. Collecting information on these first dust grains is difficult because of the negative alliance of large distances and low dust masses. Aims. We aim to combine the observational information from galaxies at redshifts 5 z 10 to constrain their dust emission and theoretically understand the first evolutionary phases of the dust cycle. Methods. Spectral energy distributions (SEDs) are fitted with CIGALE and the physical parameters and their evolution are modelled. From this SED fitting, we built a dust-emission template for this population of galaxies in the reionisation epoch. Results. Our new models explain why some early galaxies are observed and others are not. We follow in time the formation of the first grains by supernovae later destroyed by other supernova blasts and expelled in the circumgalactic and intergalactic media. Conclusions. We find evidence for the first dust grains formed in the universe. But above all, this work underlines the need to collect more data and to develop new facilities to further constrain the dust cycle in galaxies in the reionisation epoch.

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  • ALMA uncovers the [C II] emission and warm dust continuum in a z = 8.31 Lyman break galaxy

    Bakx, Tom J. L. C., Tamura, Yoichi, Hashimoto, Takuya, Inoue, Akio K., Lee, Minju M., Mawatari, Ken, Ota, Kazuaki, Umehata, Hideki, Zackrisson, Erik, Hatsukade, Bunyo, Kohno, Kotaro, Matsuda, Yuichi, Matsuo, Hiroshi, Okamoto, Takashi, Shibuya, Takatoshi, Shimizu, Ikkoh, Taniguchi, Yoshiaki, Yoshida, Naoki

    Monthly Notices of the Royal Astronomical Society    2020.04

     View Summary

    We report on the detection of the [C II] 157.7 μm emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [O III] 88 μm (from previous campaigns) to [C II] is 9.3 ± 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photodissociation regions. The emission of [C II] is cospatial to the 850 μm dust emission (90 μm rest frame, from previous campaigns), however the peak [C II] emission does not agree with the peak [O III] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 μm rest frame) down to 18 μJy (3σ). This non-detection places a strong limits on the dust spectrum, considering the 137 ± 26 μJy continuum emission at 850 μm. This suggests an unusually warm dust component (T &gt; 80 K, 90 per cent confidence limit), and/or a steep dust-emissivity index (βdust &gt; 2), compared to galaxy-wide dust emission found at lower redshifts (typically T ∼ 30-50 K, βdust ∼ 1-2). If such temperatures are common, this would reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization....

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  • Detectability of 21-cm signal during the epoch of reionization with 21-cm-Lyman-α emitter cross-correlation - III. Model dependence

    Kenji Kubota, Akio K. Inoue, Kenji Hasegawa, Keitaro Takahashi

    Monthly Notices of the Royal Astronomical Society   494 ( 3 ) 3131 - 3140  2020

     View Summary

    Detecting HI 21-cm line in the intergalactic medium during the epoch of reionization suffers from foreground contamination such as Galactic synchrotron and extragalactic radio sources. Cross-correlation between the 21-cm line and Lyman-α emitter (LAE) galaxies is a powerful tool to identify the 21-cm signal since the 21-cm line emission has correlationwith LAEs,while the LAEs are statistically independent of the foregrounds. So far, the detectability of 21-cm- LAE cross-power spectrum has been investigated with simple LAEmodels where the observed Lyα luminosity is proportional to the dark matter halo mass. However, the previous models were inconsistent with the latest observational data of LAEs obtained with Subaru/Hyper Suprime-Cam (HSC). Here, we revisit the detectability of 21-cm-LAE cross-power spectrum adopting a state-of-the-art LAE model consistent with all Subaru/HSC observations such as the Lyα luminosity function, LAE angular autocorrelation, and the LAE fractions in the continuum selected galaxies. We find that resultant cross-power spectrum with the updated LAE model is reduced at small scales (k ∼ 1 Mpc-1) compared to the simple models, while the amplitudes at large scales (k ≲ 0.2 Mpc-1) are not affected so much. We conclude that the large-scale signal would be detectable with Square Kilometre Array (SKA) and HSC LAE cross-correlation but detecting the small-scale signal would require an extended HSC LAE survey with an area of ∼ 75 deg2or 3000 h observation time of 21-cm line with SKA.

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  • ALMA uncovers the [CII] emission and warm dust continuum in a z = 8.31 Lyman break galaxy

    Bakx, Tom J. L. C., Tamura, Yoichi, Hashimoto, Takuya, Inoue, Akio K., Lee, Minju M., Mawatari, Ken, Ota, Kazuaki, Umehata, Hideki, Zackrisson, Erik, Hatsukade, Bunyo, Kohno, Kotaro, Matsuda, Yuichi, Matsuo, Hiroshi, Okamoto, Takashi, Shibuya, Takatoshi, Shimizu, Ikkoh, Taniguchi, Yoshiaki, Yoshida, Naoki

    Monthly Notices of the Royal Astronomical Society   493 ( 3 ) 4294 - 4307  2020.01  [Refereed]

     View Summary

    We report on the detection of the [CII] 157.7 $\mu$m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [OIII] 88 $\mu$m (from previous campaigns) to [CII] is 9.31 $\pm$ 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photo-dissociation regions. The emission of [CII] is cospatial to the 850 $\mu$m dust emission (90 $\mu$m rest-frame, from previous campaigns), however the peak [CII] emission does not agree with the peak [OIII] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 $\mu$m rest-frame) down to 18 $\mu$Jy (3$\sigma$). This nondetection places a strong limit on the dust spectrum, considering the 137 $\pm$ 26 $\mu$Jy continuum emission at 850 $\mu$m. This suggests an unusually warm dust component (T $&gt;$ 80 K, 90% confidence limit), and/or a steep dust-emissivity index ($\beta_{\rm dust}$ $&gt;$ 2), compared to galaxy-wide dust emission found at lower redshifts (typically T $\sim$ 30 - 50 K, $\beta_{\rm dust}$ $\sim$ 1 - 2). If such temperatures are common, this would reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization....

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  • Detections of [O III] 88 μm in two quasars in the reionization epoch

    Hashimoto, Takuya, Inoue, Akio K., Tamura, Yoichi, Matsuo, Hiroshi, Mawatari, Ken, Yamaguchi, Yuki

    Publications of the Astronomical Society of Japan    2019.12  [Refereed]

     View Summary

    We report on detections with the Atacama Large Millimeter/sub-millimeter Array of the far-infrared [O III] 88 μm line and the underlying dust continuum in two quasars in the reionization epoch, J205406.48-000514.8 (hereafter J2054-0005) at z = 6.0391 ± 0.0002 and J231038.88+185519.7 (hereafter J2310+1855) at z = 6.0035 ± 0.0007. The [O III] luminosities of J2054-0005 and J2310+1855 are L[O III] = (6.8 ± 0.6) × 109 and (2.4 ± 0.6) × 109 L, corresponding to ̃0.05% and 0.01% of the total infrared luminosity, LTIR, respectively. Combining these [O III] luminosities with [C II] 158 μm luminosities in the literature, we find that J2054-0005 and J2310+1855 have [O III]-to-[C II] luminosity ratios of 2.1 ± 0.4 and 0.3 ± 0.1, respectively, the latter of which is the lowest among objects so far reported at z &gt; 6. Combining [O III] observations at z ≈ 6-9 from our study and the literature, we identify the [O III] line deficit: objects with a larger LTIR (total infrared luminosity) have lower L[O III]-to-LTIR ratios. Furthermore, we also find that the anti-correlation is shifted toward a higher LTIR value when compared with the local [O III] line deficit....

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  • Panchromatic Analysis for Nature of HIgh-z galaxies Tool (PANHIT)

    Ken Mawatari, Akio K. Inoue, Satoshi Yamanaka, Takuya Hashimoto, Yoichi Tamura

    Proceedings of the International Astronomical Union   15 ( S341 ) 285 - 286  2019.11

     View Summary

    <title>Abstract</title>We have developed a new SED fitting tool specialized for frontier redshift galaxies. It is a common case for high-<italic>z</italic> galaxies that the available data are restricted to rich optical to near-infrared photometry and few far-infrared (FIR) data deep enough to detect the faint object (e.g., <italic>HST</italic>/WFC3 + <italic>Spitzer</italic>/IRAC + ALMA). In such situation, one cannot perform a complicated modeling of dust emission in FIR regime. We then adopt simple treatment for the dust emission using empirical LIRG templates. Instead, we adopt a sophisticated and physically motivated modeling for stellar and nebular emission parts in rest-frame UV-to-optical regime. Our new code fits not only broad band photometry but also spectral emission line flux. There is an option to fit observed SED with two templates with different physical properties. Our new code, PANHIT, is now in public, and was already applied to some high-<italic>z</italic> frontier galaxies.

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  • ALMA detection of the [OIII] 88 μm line in a highly-magnified Lyman break galaxy at z = 6.1

    Kaho Sunaga, Yoichi Tamura, Minju Lee, Ken Mawatari, Akio K. Inoue, Takuya Hashimoto, Hiroshi Matsuo, Akio Taniguchi

    Proceedings of the International Astronomical Union   15 ( S341 ) 309 - 311  2019.11

     View Summary

    <title>Abstract</title>We present a 4.7σ detection of the [OIII] 88 <italic>μ</italic>m line in a gravitationally-lensed Lyman break galaxy, RXC J2248-ID3, using the Atacama Large Millimeter/submillimeter Array (ALMA). We did not detect [CII] 158 <italic>μ</italic>m and rest-frame 90 <italic>μ</italic>m dust continuum emission, suggesting that the bulk of the interstellar medium (ISM) is ionized. Our two-component SED model combining the previous Hubble Space Telescope (HST) data and new photometry obtained from Very Large Telescope (VLT), Spitzer and ALMA suggests the presence of young (∼2 Myr) and mature (∼600 Myr) stellar components with the metallicity of <italic>Z</italic> = 0.2Z. Our findings are in contrast with previous results claiming a very young, metal-poor stellar component.

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  • Dust evolution in galaxies at z > 7

    Tsutomu T. Takeuchi, Ryosuke S. Asano, Sayaka Nagasaki, Takaya Nozawa, Yoichi Tamura, Ken Mawatari, Akio K. Inoue

    Proceedings of the International Astronomical Union   15 ( S341 ) 312 - 313  2019.11

     View Summary

    <title>Abstract</title>Recently huge amount of dust <italic>M</italic>dust ≃ 106−7<italic>M</italic> in galaxies at <italic>z</italic> = 7–8 has been discovered by ALMA observations. The suggested timescale of the dust production was a few–several×108 yr, while the stellar mass was several × 109<italic>M</italic>. This amount of dust cannot be easily explained only by a supply from supernovae if we consider the dust destruction by reverse shocks. We propose that these values can be consistently explained if we take into account the grain growth in the interstellar medium (ISM). This scenario successfully reproduces the evolution of the dust mass, as well as the SFR, and stellar mass simultaneously. We conclude that even at such an early epoch of the Universe, the dust grain growth in the ISM plays a significant role in galaxies.

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  • 3D Distribution Map of HI Gas and Galaxies Around an Enormous Ly$α$ Nebula and Three QSOs at $z=2.3$ Revealed by the HI Tomographic Mapping Technique

    Shiro Mukae, Masami Ouchi, Zheng Cai, Khee-Gan Lee, J. Xavier Prochaska, Sebastiano Cantalupo, Zheng Zheng, Kentaro Nagamine, Nao Suzuki, John D. Silverman, Toru Misawa, Akio K. Inoue, Joseph F. Hennawi, Yuichi Matsuda, Ken Mawatari, Yuma Sugahara, Takashi Kojima, Yoshiaki Ono, Takatoshi Shibuya, Yuichi Harikane, Seiji Fujimoto, Yi-Kuan Chiang, Haibin Zhang, Ryota Kakuma

    Astrophysical Journal   896 ( 1 )  2019.10

     View Summary

    We present an IGM HI tomography map in a survey volume of $16 \times 19<br />
    \times 131 \ h^{-3} {\rm comoving \ Mpc}^{3}$ (cMpc$^3$) centered at MAMMOTH-1<br />
    nebula and three neighbouring quasars at $z=2.3$. MAMMOTH-1 nebula is an<br />
    enormous Ly$\alpha$ nebula (ELAN), hosted by a type-II quasar dubbed<br />
    MAMMOTH1-QSO, that extends over $1\ h^{-1}$ cMpc with not fully clear physical<br />
    origin. Here we investigate the HI-gas distribution around MAMMOTH1-QSO with<br />
    the ELAN and three neighbouring type-I quasars, making the IGM HI tomography<br />
    map with a spatial resolution of $2.6\ h^{-1}$ cMpc. Our HI tomography map is<br />
    reconstructed with HI Ly$\alpha$ forest absorption of bright background objects<br />
    at $z=2.4-2.9$: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate<br />
    the radial profile of HI flux overdensity for MAMMOTH1-QSO, and find that<br />
    MAMMOTH1-QSO resides in a volume with significantly weak HI absorption. This<br />
    suggests that MAMMOTH1-QSO has a proximity zone where quasar illuminates and<br />
    photo-ionizes the surrounding HI gas and suppresses HI absorption, and that the<br />
    ELAN is probably a photo-ionized cloud embedded in the cosmic web. The HI<br />
    radial profile of MAMMOTH1-QSO is very similar to those of three neighbouring<br />
    type-I quasars at $z=2.3$, which is compatible with the AGN unification model.<br />
    We compare the distributions of the HI absorption and star-forming galaxies in<br />
    our survey volume, and identify a spatial offset between density peaks of<br />
    star-forming galaxies and HI gas. This segregation may suggest anisotropic UV<br />
    background radiation created by star-forming galaxy density fluctuations.

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  • Subaru narrow-band imaging search for Lyman continuum from galaxies at z > 3 in the GOODS-N field

    Ikuru Iwata, Akio K. Inoue, Genoveva Micheva, Yuichi Matsuda, Toru Yamada

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   488 ( 4 ) 5671 - 5689  2019.10

     View Summary

    We report results of a search for galaxies at z > 3 with Lyman continuum (LyC) emission using a narrow-band filter NB359 with Subaru/Suprime-Cam in an similar to 800 arcmin(2) blank field around the GOODS-N. We use 103 star-forming galaxies (SFGs) and 8 active galactic nuclei (AGNs) with spectroscopic redshifts in a range between 3.06 and 3.5 and 157 photometrically selected z = 3.1 Lyman a emitter (LAE) candidates as the targets. After removing galaxies spectroscopically confirmed to be contaminated by foreground sources, we found two SFGs and one AGN as candidate LyC-emitting sources among the targets with spectroscopic redshifts. Among LAE candidates, five sources are detected in the NB359 image, and three among them may be contaminated by foreground sources. We compare the sample galaxies in the GOODS-N with those in the SSA22, where a prominent protocluster at z = 3.1 is known and an LyC search using the same NB359 filter has been made. The frequency of galaxies with LyC leakage in the SSA22 field may be about two times higher than that of galaxies in the GOODS-N with the sample ultraviolet (UV) magnitude range, although the numbers of LyC detections in these fields are too small to make a statistically significant conclusion. By combining the sample galaxies in these fields, we place the 3 sigma upper limits of the observed LyC-to-UV flux density ratio and LyC escape fraction for galaxies at z = 3.1 with absolute UV magnitude M-UV < -18.8 as (f(LyC)/f(UV))(obs) < 0.036 and f(esc)(abs) < 8 per cent, respectively.

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  • Large Population of ALMA Galaxies at z&gt;6 with Very High [OIII]88um to [CII]158um Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?

    Harikane, Yuichi, Ouchi, Masami, Inoue, Akio K., Matsuoka, Yoshiki, Tamura, Yoichi, Bakx, Tom, Fujimoto, Seiji, Moriwaki, Kana, Ono, Yoshiaki, Nagao, Tohru, Tadaki, Ken-ichi, Kojima, Takashi, Shibuya, Takatoshi, Egami, Eiichi, Ferrara, Andrea, Gallerani, Simona, Hashimoto, Takuya, Kohno, Kotaro, Matsuda, Yuichi, Matsuo, Hiroshi, Pallottini, Andrea, Sugahara, Yuma, Vallini, Livia

    Astrophysical Journal   896 ( 2 )  2019.10  [Refereed]

     View Summary

    We present our new ALMA observations targeting [OIII]88um, [CII]158um, [NII]122um, and dust continuum emission for three Lyman break galaxies at z=6.0293-6.2037 identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [OIII] and [CII] lines from all of the galaxies at 4.3-11.8sigma levels, and identify multi-band dust continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z&gt;6, we confirm that all the nine z=6-9 galaxies have high [OIII]/[CII] ratios of L[OIII]/L[CII]~3-20, ~10 times higher than z~0 galaxies. We also find a positive correlation between the [OIII]/[CII] ratio and the Lya equivalent width (EW) at the &gt;91% confidence level. We carefully investigate physical origins of the high [OIII]/[CII] ratios at z=6-9 using Cloudy, and find that high density of the interstellar medium, low C/O abundance ratio, and the cosmic microwave background attenuation are responsible to only a part of the z=6-9 galaxies. Instead, the observed high [OIII]/[CII] ratios are explained by 10-100 times higher ionization parameters or low photodissociation region (PDR) covering fractions of 0-10%, both of which are consistent with our [NII] observations. The latter scenario can be reproduced with a density bounded nebula with PDR deficit, which would enhance the Lya, Lyman continuum, and C+ ionizing photons escape from galaxies, consistent with the [OIII]/[CII]-Lya EW correlation we find. <P />...

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  • ADF22: Blind Detections of [C II] Line Emitters Shown to be Spurious

    Natsuki H. Hayatsu, R. J. Ivison, Paola Andreani, Hideki Umehata, Yuichi Matsuda, Naoki Yoshida, Kotaro Kohno, Bunyo Hatsukade, Akio K. Inoue, Yoichi Tamura, Tutomu T. Takeuchi, Seiji Fujimoto, Minju M. Lee, Tohru Nagao, Yiping Ao

    Research Notes of the AAS    2019.07  [Refereed]

     View Summary

    We report Atacama Large Millimetre/submillimeter Array (ALMA) Cycle-5
    follow-up observations of two candidate [CII] emitters at z ~ 6 in the ALMA
    deep field in SSA22 (ADF22). The candidates were detected blindly in a Cycle-2
    ALMA survey covering ~ 5 square arcmins, with a single tuning, along with two
    CO lines associated with galaxies at lower redshifts. Various tests suggested
    at least one of the two > 6-sigma [CII] candidates should be robust (Hayatsu et
    al. 2017). Nevertheless, our new, deeper observations recover neither
    candidate, demonstrating a higher contamination rate than expected. The cause
    of the spurious detections is under investigation but at present it remains
    unclarified.

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  • The absence of [C II] 158 μm emission in spectroscopically confirmed galaxies at z &gt; 8

    Laporte, N., Katz, H., Ellis, R. S., Lagache, G., Bauer, F. E., Boone, F., Inoue, A. K., Hashimoto, T., Matsuo, H., Mawatari, K., Tamura, Y.

    Monthly Notices of the Royal Astronomical Society    2019.07  [Refereed]

     View Summary

    The scatter in the relationship between the strength of [C II] 158 μm emission and the star formation rate at high redshift has been the source of much recent interest. Although the relationship is well established locally, several intensely star-forming galaxies have been found whose [C II] 158 μm emission is either weak, absent, or spatially offset from the young stars. Here we present new ALMA data for the two most distant gravitationally lensed and spectroscopically confirmed galaxies, A2744_YD4 at z = 8.38 and MACS1149_JD1 at z = 9.11, both of which reveal intense [O III] 88 μm emission. In both cases we provide stringent upper limits on the presence of [C II] 158 μm with respect to [O III] 88 μm. We review possible explanations for this apparent redshift-dependent [C II] deficit in the context of our recent hydrodynamical simulations. Our results highlight the importance of using several emission line diagnostics with ALMA to investigate the nature of the interstellar medium in early galaxies....

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  • SILVERRUSH. VII. Subaru/HSC Identifications of Protocluster Candidates at z similar to 6-7: Implications for Cosmic Reionization

    Higuchi Ryo, Ouchi Masami, Ono Yoshiaki, Shibuya Takatoshi, Toshikawa Jun, Harikane Yuichi, Kojima Takashi, Chiang Yi-Kuan, Egami Eiichi, Kashikawa Nobunari, Overzier Roderik, Konno Akira, Inoue Akio K, Hasegawa Kenji, Fujimoto Seiji, Goto Tomotsugu, Ishikawa Shogo, Ito Kei, Komiyama Yutaka, Tanaka Masayuki

    ASTROPHYSICAL JOURNAL   879 ( 1 ) 28 - 28  2019.07  [Refereed]

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  • SILVERRUSH. IX. Ly$α$ Intensity Mapping with Star-Forming Galaxies at $z=5.7$ and $6.6$: Ly$α$ Emission Extended at $>150$ comoving kpc Beyond the Virial-Radius Scale of Galaxy Dark Matter Halos

    Ryota Kakuma, Masami Ouchi, Yuichi Harikane, Akio K Inoue, Yutaka Komiyama, Haruka Kusakabe, Chien-Hsiu Liu, Yuichi Matsuda, Yoshiki Matsuoka, Ken Mawatari, Rieko Momose, Yoshiaki Ono, Takatoshi Shibuya, Yoshiaki Taniguchi

    Astrophysical Journal   916 ( 1 )  2019.06

     View Summary

    We present results of the cross-correlation Lya intensity mapping with<br />
    Subaru/Hyper Suprime-Cam (HSC) ultra-deep narrowband images and Lya emitters<br />
    (LAEs) at $z=5.7$ and $6.6$ in a total area of $4$ deg$^2$. Although<br />
    overwhelming amount of data quality controls have been performed for the<br />
    narrowband images and the LAE samples, we further conduct extensive analysis<br />
    evaluating systematics of large-scale point spread function wings, sky<br />
    subtractions, and unknown errors on the basis of physically uncorrelated<br />
    signals and sources found in real HSC images and object catalogs, respectively.<br />
    Removing the systematics, we carefully calculate cross-correlations between Lya<br />
    intensity of the narrowband images and the LAEs. We identify very diffuse Lya<br />
    emission with the $3\sigma$ ($2\sigma$) significance at $&gt;150$ comoving kpc<br />
    (ckpc) far from the LAEs at $z = 5.7$ ($6.6$), beyond a virial radius of<br />
    star-forming galaxies with $M_\mathrm{h} \sim 10^{11} M_\odot$. The diffuse Lya<br />
    emission possibly extends up to $1,000$ ckpc with the surface brightness of<br />
    $10^{-20}-10^{-19}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. We confirm that the<br />
    small-scale ($&lt;150$ ckpc) Lya radial profiles of LAEs in our Lya intensity maps<br />
    are consistent with those obtained by recent MUSE observations (Leclercq et al.<br />
    2017). Comparisons with numerical simulations suggest that the large-scale<br />
    ($\sim 150-1,000$ ckpc) Lya emission are not explained by unresolved faint<br />
    sources of neighboring galaxies including satellites, but by a combination of<br />
    Lya photons emitted from the central LAE and other unknown sources, such as a<br />
    cold-gas stream and galactic outflow. We find no evolution in the Lya radial<br />
    profiles of our LAEs from $z=5.7$ to $6.6$, where theoretical models predict a<br />
    flattening of the profile slope made by cosmic reionization, albeit with our<br />
    moderately large observational errors.

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  • Exploration and characterization of the earliest epoch of galaxy formation: beyond the re-ionization era

    Kohno, Kotaro, Tamura, Yoichi, Inoue, Akio, Kawabe, Ryohei, Oshima, Tai, Hatsukade, Bunyo, Takekoshi, Tatsuya, Yoshimura, Yuki, Umehata, Hideki, Dannerbauer, Helmut, Cicone, Claudia, Bertoldi, Frank

    Astro2020: Decadal Survey on Astronomy and Astrophysics    2019.05  [Refereed]

     View Summary

    Recent ALMA detection of the bright [OIII] 88 um line at z = 9.11, indicates the onset of star formation at z 15. In order to uncover a large number of z=10-15 galaxies, we argue two possible pathways: (1) a blind spectroscopic survey of [OIII] 88 um line emitters, and (2) a high-cadence survey of transient sources to catch the pop-III GRBs. <P />...

  • CHORUS. III. Photometric and Spectroscopic Properties of Ly$α$ Blobs at $z=4.9-7.0$

    Zhang} Haibin, Ouchi} Masami, Itoh} Ryohei, Shibuya} Takatoshi, Ono} Yoshiaki, Harikane} Yuichi, Inoue, Akio K, Rauch} Michael, Kikuchihara} Shotaro, Nakajima} Kimihiko, Yajima} Hidenobu, Arata} Shohei, Abe} Makito, Iwata} Ikuru, Kashikawa} Nobunari, Kawanomoto} Satoshi, Kikuta} Satoshi, Kobayashi, Masakazu, Kusakabe} Haruka, Mawatari} Ken, Nagao} Tohru, Shimasaku} Kazuhiro, Taniguchi} Yoshiaki

    arXiv e-prints   891 ( 2 ) arXiv:1905.09841  2019  [Refereed]

     View Summary

    We report the Subaru Hyper Suprime-Cam (HSC) discovery of two Ly alpha blobs (LABs), dubbed z70-1 and z49-1 at z = 6.965 and z = 4.888, respectively, that are Ly alpha emitters with a bright (log Lly alpha/[crg s(-1)] > 43.4 and and spatially extended Ly alpha emission, and present the photometric and spectroscopic properties of a total of seven LABs: the two new LABs and five previously known LABs at z = 5.7-6.6. The z70-1 LAB shows extended Ly alpha emission with a scale length of 1.4 +/- 0.2 kpc, about three times larger than the UV continuum emission, making z70-1 the most distant LAB identified to date. All of the seven LABs, except z49-1, exhibit no active galactic nucleus (AGN) signatures such as X-ray emission, N v lambda 1240 emission, or Ly alpha line broadening, while z49-1 has a strong C iv lambda 1548 emission line indicating an AGN on the basis of the UV-line ratio diagnostics. We carefully model the point-spread functions of the HSC images and conduct two-component exponential profile fitting to the extended Ly alpha emission of the LABs. The Ly alpha scale lengths of the core (star-forming region) and halo components are r(c) = 0.6-1.2 kpc and r(h) = 2.0-13.8 kpc, respectively. The relations between the scale lengths and galaxy properties (Ly alpha luminosity L-Ly alpha, Ly alpha rest-frame equivalent width EW0, and UV continuum magnitude M-UV) of our LABs are similar to those of Ly alpha halos (LAHs) identified around star-forming galaxies found previously by the Very Large Telescope/MUSE at similar redshifts, suggesting that our LABs are likely the bright version of high-z LAHs.

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  • SILVERRUSH. VIII. Spectroscopic Identications of Early Large Scale Structures with Protoclusters Over 200 Mpc at z=6-7: Strong Associations of Dusty Star-Forming Galaxies

    Yuichi Harikane, Masami Ouchi, Yoshiaki Ono, Seiji Fujimoto, Darko Donevski, Takatoshi Shibuya, Andreas L. Faisst, Tomotsugu Goto, Bunyo Hatsukade, Nobunari Kashikawa, Kotaro Kohno, Takuya Hashimoto, Ryo Higuchi, Akio K. Inoue, Yen-Ting Lin, Crystal L. Martin, Roderik Overzier, Ian Smail, Jun Toshikawa, Hideki Umehata, Yiping Ao, Scott Chapman, David L. Clements, Myungshin Im, Yipeng Jing, Toshihiro Kawaguchi, Chien-Hsiu Lee, Minju M. Lee, Lihwai Lin, Yoshiki Matsuoka, Murilo Marinello, Tohru Nagao, Masato Onodera, Sune Toft, Wei-Hao Wang

    The Astrophysical Journal   883 ( 2 ) 142 - 142  2019  [Refereed]

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  • The distribution and physical properties of high-redshift [O III] emitters in a cosmological hydrodynamics simulation

    Moriwaki, Kana, Yoshida, Naoki, Shimizu, Ikkoh, Harikane, Yuichi, Matsuda, Yuichi, Matsuo, Hiroshi, Hashimoto, Takuya, Inoue, Akio K., Tamura, Yoichi, Nagao, Tohru

    Monthly Notices of the Royal Astronomical Society    2018.11  [Refereed]

     View Summary

    Recent observations with the Atacama Large Millimeter/submillimeter Array (ALMA) detected far-infrared emission lines such as the [O III] 88 μ m line from galaxies at z ̃ 7-9. We use a cosmological simulation of galaxy formation to study the physical properties of [O III] 88 μ m emitters. In a comoving volume of 50 h-1 Mpc on a side, we locate 34 galaxies with stellar masses greater than 10^8 M_{☉} at z = 9, and more than 270 such galaxies at z = 7. We calculate the [O III] 88 μ m luminosities (L_{O III}, 88) by combining a physical model of H II regions with emission line calculations using the photoionization code CLOUDY. We show that the resulting L_{O III}, 88, for a given star formation rate, is slightly higher than predicted from the empirical relation for local galaxies, and is consistent with recent observations of galaxies at redshifts 7-9. Bright [O III] emitters with L_{O III}, 88 &gt; 10^8 L_{☉} have star formation rates higher than 3 M_{☉} yr^{-1}, and the typical metallicity is {̃ } 0.1 Z_{☉}. The galaxies are hosted by dark matter haloes with masses greater than 10^{11} M_{☉}. We propose to use the [O III] 5007 Å line, to be detected by James Webb Space Telescope, to study the properties of galaxies whose [O III] 88 μ m line emission has been already detected with ALMA....

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  • CHORUS. II. Subaru/HSC Determination of the Ly alpha Luminosity Function at z=7.0: Constraints on Cosmic Reionization Model Parameter

    Itoh Ryohei, Ouchi Masami, Zhang Haibin, Inoue Akio K, Mawatari Ken, Shibuya Takatoshi, Harikane Yuichi, Ono Yoshiaki, Kusakabe Haruka, Shimasaku Kazuhiro, Fujimoto Seiji, Iwata Ikuru, Kajisawa Masaru, Kashikawa Nobunari, Kawanomoto Satoshi, Komiyama Yutaka, Lee Chien-Hsiu, Nagao Tohru, Taniguchi Yoshiaki

    ASTROPHYSICAL JOURNAL   867 ( 1 )  2018.11  [Refereed]

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  • Detections of [OIII] 88 $\mu$m in Two Quasars in the Reionization Epoch

    Hashimoto, Takuya, Inoue, Akio K., Tamura, Yoichi, Matsuo, Hiroshi, Mawatari, Ken, Yamaguchi, Yuki

       2018.10  [Refereed]

     View Summary

    With the Atacama Large Millimeter/sub-millimeter Array (ALMA), we report detections of the far-infrared (FIR) [OIII] 88 $\mu$m line and the underlying dust continuum in the two quasars in the reionization epoch, J205406.48-000514.8 (hereafter J2054-0005) at $z=6.0391\pm0.0002$ and J231038.88+185519.7 (hereafter J2310+1855) at $z=6.0035\pm0.0007$. The [OIII] luminosity of J2054-0005 and J2310+1855 are $L_{\rm [OIII]} = (6.8\pm0.6) \times 10^{9}$ and $(2.4\pm0.6) \times 10^{9}$ $L_{\rm \odot}$, corresponding to $\approx$ 0.05\%\ and 0.01\%\ of the total infrared luminosity, $L_{\rm TIR}$, respectively. Combining these [OIII] luminosities with [CII] 158 $\mu$m luminosities in the literature, we find that J2054-0005 and J2310+1855 have the [OIII]-to-[CII] luminosity ratio of $2.1\pm0.4$ and $0.3\pm0.1$, respectively, the latter of which is the lowest among objects so far reported at $z&gt;6$. Combining [OIII] observations at $z\approx6-9$ from our study and the literature, we identify the [OIII] line deficit: objects with larger $L_{\rm TIR}$ have lower $L_{\rm [OIII]}$-to-$L_{\rm TIR}$ ratios. Furthermore, we also find that the anti-correlation is shifted toward higher $L_{\rm TIR}$ value when compared to the local [OIII] line deficit. <P />...

  • SILVERRUSH. V. Census of Lyα, [O III] λ5007, Hα, and [C II] 158 μm Line Emission with ∼1000 LAEs at z = 4.9-7.0 Revealed with Subaru/HSC

    Yuichi Harikane, Masami Ouchi, Takatoshi Shibuya, Takashi Kojima, Haibin Zhang, Ryohei Itoh, Yoshiaki Ono, Ryo Higuchi, Akio K. Inoue, Jacopo Chevallard, Peter L. Capak, Tohru Nagao, Masato Onodera, Andreas L. Faisst, Crystal L. Martin, Michael Rauch, Gustavo A. Bruzual, Stephane Charlot, Iary Davidzon, Seiji Fujimoto, Miftahul Hilmi, Olivier Ilbert, Chien-Hsiu Lee, Yoshiki Matsuoka, John D. Silverman, Sune Toft

    Astrophysical Journal   859 ( 2 ) article id. 84, 21 pp.  2018.06  [Refereed]

     View Summary

    We investigate Lyα, [O iii] λ5007, Hα, and [C ii] 158 μm emission from 1124 galaxies at z = 4.9-7.0. Our sample is composed of 1092 Lyα emitters (LAEs) at z = 4.9, 5.7, 6.6, and 7.0 identified by Subaru/Hyper-Suprime-Cam (HSC) narrowband surveys covered by Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) and 34 galaxies at z = 5.148-7.508 with deep ALMA [C ii] 158 μm data in the literature. Fluxes of strong rest-frame optical lines of [O iii] and Hα (Hβ) are constrained by significant excesses found in the SPLASH 3.6 and 4.5 μm photometry. At z = 4.9, we find that the rest-frame Hα equivalent width and the Lyα escape fraction f Lyα positively correlate with the rest-frame Lyα equivalent width fLyα positively correlate with the rest-frame Lyα equivalent width EWLyα0 . The correlation is similarly found at z ∼ 0-2, suggesting no evolution of the correlation over z ≃ 0-5. The typical ionizing photon production efficiency of LAEs is log(ξ ion/[Hz erg-1]) ≃ 25.5, significantly (60%-100%) higher than those of LBGs at a given UV magnitude. At z = 5.7-7.0, there exists an interesting turnover trend that the [O iii]/Hα flux ratio increases in and then decreases out to . We also identify an anticorrelation between a ratio of [C ii] luminosity to star formation rate (L [C ii]/SFR) and at the &gt
    99% confidence level.. We carefully investigate physical origins of the correlations with stellar-synthesis and photoionization models and find that a simple anticorrelation between and metallicity explains self-consistently all of the correlations of Lyα, Hα, [O iii]/Hα, and [C ii] identified in our study, indicating detections of metal-poor (∼0.03 Z o) galaxies with .

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  • Hubble Space Telescope Wide Field Camera 3 Observations of Escaping Lyman Continuum Radiation from Galaxies and Weak AGN at Redshifts z ∼ 2.3-4.1

    Brent M. Smith, Rogier A. Windhorst, Rolf A. Jansen, Seth H. Cohen, Linhua Jiang, Mark Dijkstra, Anton M. Koekemoer, Richard Bielby, Akio K. Inoue, John W. Mackenty, Robert W. O'Connell, Joseph I. Silk

    Astrophysical Journal   853 ( 2 ) article id. 191, 30 pp.  2018.02  [Refereed]

     View Summary

    We present observations of escaping Lyman Continuum (LyC) radiation from 34 massive star-forming galaxies (SFGs) and 12 weak AGN with reliably measured spectroscopic redshifts at z ≅ 2.3-4.1. We analyzed Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) mosaics of the Early Release Science (ERS) field in three UVIS filters to sample the rest-frame LyC over this redshift range. With our best current assessment of the WFC3 systematics, we provide 1s upper limits for the average LyC emission of galaxies at 〈z〉 = 2.35, 2.75, and 3.60 to ∼28.5, 28.1, and 30.7 mag in image stacks of 11-15 galaxies in the WFC3/UVIS F225W, F275W, and F336W, respectively. The LyC flux of weak AGN at 〈z〉 = 2.62 and 3.32 are detected at 28.3 and 27.4 mag with S/Ns of ∼2.7 and 2.5 in F275W and F336W for stacks of 7 and 3 AGN, respectively, while AGN at 〈z〉 = 2.37 are constrained to ≳27.9 mag at 1s in a stack of 2 AGN. The stacked AGN LyC light profiles are flatter than their corresponding non-ionizing UV continuum profiles out to radii of r ≲ 0.″9, which may indicate a radial dependence of porosity in the ISM. With synthetic stellar SEDs fit to UV continuum measurements longward of Lya and IGM transmission models, we constrain the absolute LyC escape fractions to fesc abs 22-22 +44% at 〈z〉 = 2.35 and ≲55% at 〈z〉= 2.75 and 3.60, respectively. All available data for galaxies, including published work, suggests a more sudden increase of fesc with redshift at z ≅ 2. Dust accumulating in (massive) galaxies over cosmic time correlates with increased H I column density, which may lead to reducing fesc more suddenly at z ≲ 2. This may suggest that SFGs collectively contributed to maintaining cosmic reionization at redshifts z ≳ 2-4, while AGN likely dominated reionization at z ≲ 2.

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  • SILVERRUSH. IV. Lya Luminosity Functions at z=5.7 and 6.6 Studied with ~2,000 LAEs on the 14-21 deg2 Sky

    Konno, A, Ouchi, M, Shibuya, T, Ono, Y, Shimasaku, K, Taniguchi, Y, Nagao, T, Kobayashi, M. A. R, Kajisawa, M, Kashikawa, N, Inoue, A. K, Oguri, M, Furusawa, H, Goto, T, Harikane, Y, Higuchi, R, Komiyama, Y, Kusakabe, H, Miyazaki, S, Nakajima, K, Wang, S.-Y

    PASJ   70   S16  2018  [Refereed]

  • The Hyper Suprime-Cam SSP survey: Overview and survey design

    Hiroaki Aihara, Nobuo Arimoto, Robert Armstrong, Stéphane Arnouts, Neta A. Bahcall, Steven Bickerton, James Bosch, Kevin Bundy, Peter L. Capak, James H. H. Chan, Masashi Chiba, Jean Coupon, Eiichi Egami, Motohiro Enoki, Francois Finet, Hiroki Fujimori, Seiji Fujimoto, Hisanori Furusawa, Junko Furusawa, Tomotsugu Goto, Andy Goulding, Johnny P. Greco, Jenny E. Greene, James E. Gunn, Takashi Hamana, Yuichi Harikane, Yasuhiro Hashimoto, Takashi Hattori, Masao Hayashi, Yusuke Hayashi, Krzysztof G. Hełminiak, Ryo Higuchi, Chiaki Hikage, Paul T. P. Ho, Bau-Ching Hsieh, Kuiyun Huang, Song Huang, Hiroyuki Ikeda, Masatoshi Imanishi, Akio K. Inoue, Kazushi Iwasawa, Ikuru Iwata, Anton T. Jaelani, Hung-Yu Jian, Yukiko Kamata, Hiroshi Karoji, Nobunari Kashikawa, Nobuhiko Katayama, Satoshi Kawanomoto, Issha Kayo, Jin Koda, Michitaro Koike, Takashi Kojima, Yutaka Komiyama, Akira Konno, Shintaro Koshida, Yusei Koyama, Haruka Kusakabe, Alexie Leauthaud, Chien-Hsiu Lee, Lihwai Lin, Yen-Ting Lin, Robert H. Lupton, Rachel Mandelbaum, Yoshiki Matsuoka, Elinor Medezinski, Sogo Mineo, Shoken Miyama, Hironao Miyatake, Satoshi Miyazaki, Rieko Momose, Anupreeta More, Surhud More, Yuki Moritani, Takashi J. M. Oriya, Tomoki Morokuma, Shiro Mukae, Ryoma Murata, Hitoshi Murayama, Tohru Nagao, Fumiaki Nakata, Mana Niida, Hiroko Niikura, Atsushi J. Nishizawa, Yoshiyuki Obuchi, Masamune Oguri, Yukie Oishi, Nobuhiro Okabe, Sakurako Okamoto, Yuki Okura, Yoshiaki Ono, Masato Onodera, Masafusa Onoue, Ken Osato, Masami Ouchi, Paul A. Price, Tae-Soo Pyo, Masao Sako, Marcin Sawicki, Takatoshi Shibuya, Kazuhiro Shimasaku, Atsushi Shimono, Masato Shirasaki, John D. Silverman, Melanie Simet, Joshua Speagle, David N. Spergel, Michael A. Strauss, Yuma Sugahara, Naoshi Sugiyama, Yasushi Suto, Sherry H. Suyu, Nao Suzuki, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Naoyuki Tamura, Manobu M. Tanaka, Masaomi Tanaka, Masayuki Tanaka, Yoko Tanaka, Tsuyoshi Terai, Yuichi Terashima, Yoshiki Toba, Nozomu Tominaga, Jun Toshikawa, Edwin L. Turner, Tomohisa Uchida, Hisakazu Uchiyama, Keiichi Umetsu, Fumihiro Uraguchi, Yu Ji Urata, Tomonori Usuda, Yousuke Utsumi, Shiang-Yu Wang, Wei-Hao Wang, Kenneth C. Wong, Kiyoto Yabe, Yoshihiko Yamada, Hitomi Yamanoi, Naoki Yasuda, Sherry Yeh, Atsunori Yonehara, Suraphong Yuma

    Publications of the Astronomical Society of Japan   70 ( 1 ) id.S4  2018.01  [Refereed]

     View Summary

    Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea in Hawaii. A team of scientists from Japan, Taiwan, and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg2 in five broad bands (grizy), with a 5 σ point-source depth of r ≈ 26. The Deep layer covers a total of 26 deg2 in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.

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  • Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program strategy and clustering properties of ∼2000 Lyα emitters at z = 6-7 over the 0.3-0.5 Gpc2 survey area

    Masami Ouchi, Yuichi Harikane, Takatoshi Shibuya, Kazuhiro Shimasaku, Yoshiaki Taniguchi, Akira Konno, Masakazu Kobayashi, Masaru Kajisawa, Tohru Nagao, Yoshiaki Ono, Akio K Inoue, Masayuki Umemura, Masao Mori, Kenji Hasegawa, Ryo Higuchi, Yutaka Komiyama, Yuichi Matsuda, Kimihiko Nakajima, Tomoki Saito, Shiang-Yu Wang

    Publications of the Astronomical Society of Japan   70 ( SP1 ) id.S13  2018.01  [Refereed]

     View Summary

    We present the SILVERRUSH program strategy and clustering properties investigated with ∼2000 Lyα emitters (LAEs) at z = 5.7 and 6.6 found in the early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrow-band filters. We derive angular correlation functions with the unprecedentedly large samples of LAEs at z = 6-7 over the large total area of 14-21 deg2 corresponding to 0.3-0.5 comoving Gpc2. We obtain the average large-scale bias values of bavg = 4.1±0.2 (4.5±0.6) at z = 5.7 (z = 6.6) for L∗ LAEs, indicating a weak evolution of LAE clustering from z = 5.7 to 6.6. We compare the LAE clustering results with two independent theoretical models that suggest an increase of an LAE clustering signal by the patchy ionized bubbles at the epoch of reionization (EoR), and estimate the neutral hydrogen fraction to be xHI = 0.15-0.15+0.15 at z = 6.6. Based on the halo occupation distributionmodels, we find that the L∗ LAEs are hosted by dark-matter halos with an average mass of log(Mh/M) = 11.1-0.4+0.2 (10.8-0.5+0.3) at z = 5.7 (6.6) with a Lyα duty cycle of 1% or less, where the results of z = 6.6 LAEs may be slightly biased, due to the increase of the clustering signal at the EoR. Our clustering analysis reveals the low-mass nature of L∗ LAEs at z = 6-7, and that these LAEs probably evolve into massive super-L∗ galaxies in the present-day universe.

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  • SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14-21 deg2 sky

    Akira Konno, Masami Ouchi, Takatoshi Shibuya, Yoshiaki Ono, Kazuhiro Shimasaku, Yoshiaki Taniguchi, Tohru Nagao, Masakazu A.R. Kobayashi, Masaru Kajisawa, Nobunari Kashikawa, Akio K Inoue, Masamune Oguri, Hisanori Furusawa, Tomotsugu Goto, Yuichi Harikane, Ryo Higuchi, Yutaka Komiyama, Haruka Kusakabe, Satoshi Miyazaki, Kimihiko Nakajima, Shiang-Yu Wang

    Publications of the Astronomical Society of Japan   70 ( SP1 ) id.S16  2018.01  [Refereed]

     View Summary

    We present the Lyα luminosity functions (LFs) at z = 5.7 and 6.6 derived from a new large sample of 1266 Lyα emitters (LAEs) identified in total areas of 14 and 21 deg2, respectively, based on the early narrowband data of the Subaru/Hyper Suprime-Cam survey. Together with careful Monte Carlo simulations that account for the incompleteness of the LAE selection and the flux estimate systematics in the narrowband imaging, we have determined the Lyα LFs with unprecedentedly small statistical and systematic uncertainties in a wide Lyα luminosity range of 1042.8-43.8 erg s-1. We obtain best-fit Schechter parameters of L∗Lyα = 1.6-0.6 +2.2 (1.7-0.7 +0.3) × 1043 erg s-1, φ∗Lyα = 0.85-0.77 +1.87 (0.47-0.44 +1.44) × 10-4 Mpc-3, and α = -2.6-0.4 +0.6 (-2.5-0.5 +0.5) at z = 5.7 (6.6). We confirm that our best-estimate Lyα LFs are consistent with the majority of the previous studies, but find that our Lyα LFs do not agree with the high number densities of LAEs recently claimed by Matthee/Santos et al.'s studies that may overcorrect the incompleteness and the flux systematics. Our Lyα LFs at z = 5.7 and 6.6 show an indication that the faint-end slope is very steep (α - -2.5), although it is also possible that the bright-end LF results are enhanced by systematic effects such as the contribution from AGNs, blended merging galaxies, and/or large ionized bubbles around bright LAEs. Comparing our Lyα LF measurements with four independent reionization models, we estimate the neutral hydrogen fraction of the intergalactic medium to be xHI = 0.3 ± 0.2 at z = 6.6, which is consistent with the small Thomson scattering optical depth obtained by Planck 2016.

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  • ALMA 26 arcmin2 Survey of GOODS-S at One-millimeter (ASAGAO): X-Ray AGN Properties of Millimeter-selected Galaxies

    Ueda, Y., Hatsukade, B., Kohno, K., Yamaguchi, Y., Tamura, Y., Umehata, H., Akiyama, M., Ao, Y., Aretxaga, I., Caputi, K., Dunlop, J. S., Espada, D., Fujimoto, S., Hayatsu, N. H., Imanishi, M., Inoue, A. K., Ivison, R. J., Kodama, T., Lee, M. M., Matsuoka, K., Miyaji, T., Morokuma-Matsui, K., Nagao, T., Nakanishi, K., Nyland, K., Ohta, K., Ouchi, M., Rujopakarn, W., Saito, T., Tadaki, K., Tanaka, I., Taniguchi, Y., Wang, T., Wang, W. -H., Yoshimura, Y., Yun, M. S.

    The Astrophysical Journal   853 ( 1 ) article id. 24, 11 pp.  2018.01  [Refereed]

     View Summary

    We investigate the X-ray active galactic nucleus (AGN) properties of millimeter galaxies in the Great Observatories Origins Deep Survey South (GOODS-S) field detected with the Atacama Large Millimeter/submillimeter Array (ALMA), by utilizing the Chandra 7-Ms data, the deepest X-ray survey to date. Our millimeter galaxy sample comes from the ASAGAO survey covering 26 arcmin2 (12 sources at a 1.2 mm flux-density limit of ≈ 0.6 mJy), supplemented by the deeper but narrower 1.3 mm survey of a part of the ASAGAO field by Dunlop et al. Ofthe 25 total millimeter galaxies, 14 have Chandra counterparts. The observed AGN fractions at z=1.5{--}3 are found to be {90}-19+8% and {57}-25+23% for the ultra-luminous and luminous infrared galaxies with log {L}{IR}/{L} = 12-12.8 and log {L}{IR}/{L} = 11.5-12, respectively. The majority (̃2/3) of the ALMA and/or Herschel detected X-ray AGNs at z = 1.5-3 appear to be star-formation-dominant populations, having {L}{ { X } }/ {L}{IR} ratios smaller than the “simultaneous evolution” value expected from the local black-hole-mass-to-stellar-mass ({M}{BH}-M *) relation. On the basis of the {L}{ { X } } and stellar mass relation, we infer that a large fraction of star-forming galaxies at z=1.5{--}3 have black hole masses that are smaller than those expected from the local {M}{BH}-M * relation. This contrasts previous reports on luminous AGNs at the same redshifts detected in wider and shallower surveys, which are subject to selection biases against lower luminosity AGNs. Our results are consistent with an evolutionary scenario in which star formation occurs first, and an AGN-dominant phase follows later, in objects that finally evolve into galaxies with classical bulges....

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  • The effect of radiation pressure on spatial distribution of dust inside HII regions

    Shohei Ishiki, Takashi Okamoto, Akio K. Inoue

    Monthly Notices of the Royal Astronomical Society   474 ( 2 ) 1935 - 1943  2018  [Refereed]

     View Summary

    We investigate the impact of radiation pressure on spatial dust distribution inside HII regions using one-dimensional radiation hydrodynamic simulations, which include absorption and reemission of photons by dust. In order to investigate grain-size effects as well, we introduce two additional fluid components describing large and small dust grains in the simulations. Relative velocity between dust and gas strongly depends on the drag force. We include collisional drag force and coulomb drag force. We find that, in a compact HII region, a dust cavity region is formed by radiation pressure. Resulting dust cavity sizes (~0.2 pc) agree with observational estimates reasonably well. Since dust inside an HII region is strongly charged, relative velocity between dust and gas is mainly determined by the coulomb drag force. Strength of the coulomb drag force is about 2 order of magnitude larger than that of the collisional drag force. In addition, in a cloud of mass 105 M⊙, we find that the radiation pressure changes the grain-size distribution insideHII regions. Since large (0.1 μm) dust grains are accelerated more efficiently than small (0.01 μm) grains, the large-to-small grain mass ratio becomes smaller by an order of magnitude compared with the initial one. Resulting dust-size distributions depend on the luminosity of the radiation source. The large and small grain segregation becomes weaker when we assume stronger radiation source, since dust grain charges become larger under stronger radiation and hence coulomb drag force becomes stronger.

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  • ALMA deep field in SSA22: Blindly detected CO emitters and [C II] emitter candidates

    Hayatsu, Natsuki H., Matsuda, Yuichi, Umehata, Hideki, Yoshida, Naoki, Smail, Ian, Swinbank, A. Mark, Ivison, Rob, Kohno, Kotaro, Tamura, Yoichi, Kubo, Mariko, Iono, Daisuke, Hatsukade, Bunyo, Nakanishi, Kouichiro, Kawabe, Ryohei, Nagao, Tohru, Inoue, Akio K., Takeuchi, Tsutomu T., Lee, Minju, Ao, Yiping, Fujimoto, Seiji, Izumi, Takuma, Yamaguchi, Yuki, Ikarashi, Soh, Yamada, Toru

    Publications of the Astronomical Society of Japan   69 ( 3 ) id.45  2017.06  [Refereed]

     View Summary

    We report the identification of four millimeter line-emitting galaxies with the Atacama Large Milli/submillimeter Array (ALMA) in SSA22 Field (ADF22). We analyze the ALMA 1.1-mm survey data, with an effective survey area of 5 arcmin2, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0{^''.}7 and rms noise of 0.8 mJy beam-1 at 36 km s-1 velocity resolution. We detect four line-emitter candidates with significance levels above 6σ. We identify one of the four sources as a CO(9-8) emitter at z = 3.1 in a member of the proto-cluster known in this field. Another line emitter with an optical counterpart is likely a CO(4-3) emitter at z = 0.7. The other two sources without any millimeter continuum or optical/near-infrared counterpart are likely to be [C II] emitter candidates at z = 6.0 and 6.5. The equivalent widths of the [C II] candidates are consistent with those of confirmed high-redshift [C II] emitters and candidates, and are a factor of 10 times larger than that of the CO(9-8) emitter detected in this search. The [C II] luminosity of the candidates are 4-7 × 108 L. The star formation rates (SFRs) of these sources are estimated to be 10-20 M yr-1 if we adopt an empirical [C II] luminosity-SFR relation. One of them has a relatively low S/N ratio, but shows features characteristic of emission lines. Assuming that at least one of the two candidates is a [C II] emitter, we derive a lower limit of [C II]-based star formation rate density (SFRD) at z ̃ 6. The resulting value of &gt;10-2 M yr-1 Mpc-3 is consistent with the dust-uncorrected UV-based SFRD. Future millimeter/submillimeter surveys can be used to detect a number of high-redshift line emitters, with which to study the star formation history in the early universe....

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  • Imaging of diffuse HI absorption structure in the SSA22 protocluster region at z=3.1

    Ken Mawatari, Akio K. Inoue, Toru Yamada, Tomoki Hayashino, Takuya Otsuka, Yuichi Matsuda, Hideki Umehata, Masami Ouchi, Shiro Mukae

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   467 ( 4 ) 3951 - 3962  2017.06  [Refereed]

     View Summary

    Using galaxies as background light sources to map intervening Ly a absorption is a novel approach to study the interplay among galaxies, the circumgalactic medium (CGM) and the intergalactic medium. Introducing a new measure of z = 3.1 HI Ly alpha absorption relative to the cosmic mean, Delta NB497, estimated from photometric data of star-forming galaxies at 3.3 less than or similar to z less than or similar to 3.5, we have made two-dimensional Delta NB497 maps in the z = 3.1 SSA22 protocluster region and two control fields (Subaru/XMM-Newton Deep Survey; Great Observatory Optical Deep Survey North) with a spatial resolution of similar to 5 comoving Mpc. The Delta NB497 measurements in the SSA22 field are systematically larger than those in the control fields, and this HI absorption enhancement extends more than 50 comovingMpc. The field-averaged (i. e. similar to 50 comovingMpc scale) Delta NB497 and the overdensity of Ly alpha emitters (LAEs) seem to be correlated, while there is no clear dependency of the Delta NB497 on the local LAE overdensity in a few comoving Mpc scale. These results suggest that diffuse HI gas spreads out in/around the SSA22 protocluster. We have also found an enhancement of Delta NB497 at a projected distance &lt; 100 physical kpc from the nearest z = 3.1 galaxies at least in the SSA22 field, which is probably due to HI gas associated with the CGM of individual galaxies. The HI absorption enhancement in the CGM-scale tends to be weaker around galaxies with stronger Ly alpha emission, which suggests that the Ly alpha escape fraction from galaxies depends on hydrogen neutrality in the CGM.

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  • Cosmic Galaxy-IGM HI Relation at z similar to 2-3 Probed in the COSMOS/UltraVISTA 1.6 Deg(2) Field

    Shiro Mukae, Masami Ouchi, Koki Kakiichi, Nao Suzuki, Yoshiaki Ono, Zheng Cai, Akio K. Inoue, Yi-Kuan Chiang, Takatoshi Shibuya, Yuichi Matsuda

    ASTROPHYSICAL JOURNAL   835 ( 2 ) article id. 281, 12 pp.  2017.02  [Refereed]

     View Summary

    We present spatial correlations of galaxies and IGM neutral hydrogen H I in the COSMOS/UltraVISTA 1.62 deg(2) field. Our data consist of 13,415 photo-z galaxies at z similar to 2-3 with K-s &lt; 23.4 and the Ly alpha forest absorption lines in the background quasar spectra selected from SDSS data with no signature of damped Ly alpha system contamination. We estimate a galaxy overdensity delta(gal) in an impact parameter of 2.5 (proper) Mpc, and calculate the Ly alpha forest fluctuations delta((F)) whose negative values correspond to the strong Ly alpha forest absorption lines. We identify weak evidence of an anti-correlation between delta(gal) and delta((F)) with a Spearman's rank correlation coefficient of -0.39 suggesting that the galaxy overdensities and the Ly alpha forest absorption lines positively correlate in space at the similar to 90% confidence level. This positive correlation indicates that high-z galaxies exist around an excess of H I gas in the Ly alpha forest. We find four cosmic volumes, dubbed A(obs), B-obs, C-obs, and D-obs, that have extremely large (small) values of delta(gal) similar or equal to 0.8 (-1) and delta((F)) similar or equal to 0.1(-0.4), three of which, B-obs-D-obs, significantly depart from the delta(gal)-delta((F)) correlation, and weaken the correlation signal. We perform cosmological hydrodynamical simulations. and compare with our observational results. Our simulations reproduce the delta(gal)-delta((F)) correlation, agreeing with the observational results. Moreover, our simulations have model counterparts of A(obs)-D-obs, and suggest that the observations pinpoint, by chance, a galaxy overdensity like a proto-cluster, gas filaments lying on the quasar sightline, a large void, and orthogonal low-density filaments. Our simulations indicate that the significant departures of B-obs-D-obs are produced by the filamentary large-scale structures and the observation sightline effects.

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  • The Spectral Evolution of the First Galaxies. III. Simulated James Webb Space Telescope Spectra of Reionization-epoch Galaxies with Lyman-continuum Leakage

    Erik Zackrisson, Christian Binggeli, Kristian Finlator, Nickolay Y. Gnedin, Jan-Pieter Paardekooper, Ikkoh Shimizu, Akio K. Inoue, Hannes Jensen, Genoveva Micheva, Sadegh Khochfar, Claudio Dalla Vecchia

    ASTROPHYSICAL JOURNAL   836 ( 1 ) article id. 78, 12 pp.  2017.02  [Refereed]

     View Summary

    Using four different suites of cosmological simulations, we generate synthetic spectra for galaxies with different Lyman-continuum escape fractions (f(esc)) at redshifts z approximate to 7-9, in the rest-frame wavelength range relevant for the James Webb Space Telescope (JWST) NIRSpec instrument. By investigating the effects of realistic star formation histories and metallicity distributions on the EW(H beta)-beta diagram (previously proposed as a tool for identifying galaxies with very high f(esc)), we find that neither of these effects are likely to jeopardize the identification of galaxies with extreme Lyman-continuum leakage. Based on our models, we expect that essentially all z approximate to 7-9 galaxies that exhibit rest-frame EW(Hb). 30 angstrom to have f(esc) &gt; 0.5. Incorrect assumptions concerning the ionizing fluxes of stellar populations or the dust properties of z &gt; 6 galaxies can in principle bias the selection, but substantial model deficiencies of this type should at the same time be evident from offsets in the observed distribution of z &gt; 6 galaxies in the EW(H beta)-beta diagram compared to the simulated distribution. Such offsets would thereby allow JWST/NIRSpec measurements of these observables to serve as input for further model refinement.

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  • Searching for candidates of Lyman continuum sources - revisiting the SSA22 field

    Genoveva Micheva, Ikuru Iwata, Akio K. Inoue, Yuichi Matsuda, Toru Yamada, Tomoki Hayashino

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   465 ( 1 ) 316 - 336  2017.02  [Refereed]

     View Summary

    We present the largest to date sample of hydrogen Lyman continuum (LyC) emitting galaxy candidates at any redshift, with 18 Lyman alpha emitters (LAEs) and seven Lyman break galaxies (LBGs), obtained from the SSA22 field with Subaru/Suprime-Cam. The sample is based on the 159 LAEs and 136 LBGs observed in the field, all with spectroscopically confirmed redshifts, and these LyC candidates are selected as galaxies with counterparts in a narrow-band filter image which traces LyC at z &gt;= 3.06. Many LyC candidates show a spatial offset between the rest-frame non-ionizing ultraviolet (UV) detection and the LyC-emitting substructure or between the Ly alpha emission and LyC. The possibility of foreground contamination complicates the analysis of the nature of LyC emitters, although statistically it is highly unlikely that all candidates in our sample are contaminated by foreground sources. Many viable LyC LAE candidates have flux density ratios inconsistent with standard models, while also having too blue UV slopes to be foreground contaminants. Stacking reveals no significant LyC detection, suggesting that there is a dearth of objects with marginal LyC signal strength, perhaps due to a bimodality in the LyC emission. The foreground contamination corrected 3 sigma upper limits of the observed average flux density ratios are f(LyC)/f(UV) &lt; 0.08 from stacking LAEs and f(LyC)/f(UV) &lt; 0.02 from stacking LBGs. There is a sign of a positive correlation between LyC and Ly alpha, suggesting that both types of photons escape via a similar mechanism. The LyC detection rate among protocluster LBGs is seemingly lower compared to the field.

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  • Lyman continuum leaking AGN in the SSA22 field

    Genoveva Micheva, Ikuru Iwata, Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   465 ( 1 ) 302 - 315  2017.02  [Refereed]

     View Summary

    Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin nature or are foreground contaminants. The remaining two LyC candidates are type I AGN. We argue that the average LyC escape fraction of high-redshift, low-luminosityAGNis not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of 2 lower than values obtained assuming f(esc) = 1. Comparing to recent Ly alpha forest measurements, AGNs at redshift z similar to 3 make up at most similar to 12 per cent and as little as similar to 5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

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  • A HARD IONIZING SPECTRUM IN z=3-4 Ly alpha EMITTERS WITH INTENSE [O III] EMISSION: ANALOGS OF GALAXIES IN THE REIONIZATION ERA?

    Kimihiko Nakajima, Richard S. Ellis, Ikuru Iwata, Akio K. Inoue, Haruka Kusakabe, Masami Ouchi, Brant E. Robertson

    ASTROPHYSICAL JOURNAL LETTERS   831 ( 1 ) article id. L9, 6 pp.  2016.11  [Refereed]

     View Summary

    We present Keck/MOSFIRE spectra of the diagnostic nebular emission lines [O III]lambda lambda 5007, 4959, [O II]lambda 3727, and H beta for a sample of 15 redshift z similar or equal to 3.1-3.7 Ly alpha emitters (LAEs) and Lyman break galaxies (LBGs). In conjunction with spectra from other surveys, we confirm earlier indications that LAEs have a much higher [O III]/[O II] line ratio than is seen in similar redshift LBGs. By comparing their distributions on a [O III]/[O II] versus R23 diagram, we demonstrate that this difference cannot arise solely because of their lower metallicities but most likely is due to a harder ionizing spectrum. Using measures of H beta and recombination theory, we demonstrate, for a subset of our LAEs, that xi(ion)-the number of Lyman continuum photons per UV luminosity-is indeed 0.2-0.5 dex larger than for typical LBGs at similar redshifts. Using photoionization models, we estimate the effect this would have on both [O III]/[O II] and R23 and conclude such a hard spectrum can only partially explain such intense line emission. The additional possibility is that such a large [O III]/[O II] ratio is in part due to density rather than ionization bound nebular regions, which would imply a high escape fraction of ionizing photons. We discuss how further observations could confirm this possibility. Clearly LAEs with intense [O III] emission represent a promising analog of those z &gt; 7 sources with similarly strong lines that are thought to be an important contributor to cosmic reionization.

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  • A HARD IONIZING SPECTRUM INz= 3–4 LyαEMITTERS WITH INTENSE $[{\rm{O } }\,{\rm{III } }]$ EMISSION: ANALOGS OF GALAXIES IN THE REIONIZATION ERA?

    Kimihiko Nakajima, Richard S. Ellis, Ikuru Iwata, Akio K. Inoue, Haruka Kusakabe, Masami Ouchi, Brant E. Robertson

    The Astrophysical Journal   831 ( 1 )  2016.10

    DOI

  • Nebular line emission from z &gt; 7 galaxies in a cosmological simulation: rest-frame UV to optical lines

    Ikkoh Shimizu, Akio K. Inoue, Takashi Okamoto, Naoki Yoshida

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   461 ( 4 ) 3563 - 3575  2016.10  [Refereed]

     View Summary

    We have performed very large and high-resolution cosmological hydrodynamic simulations in order to investigate detectability of nebular lines in the rest-frame ultraviolet (UV) to optical wavelength range from galaxies at z &gt; 7. We find that the expected line fluxes are very well correlated with the apparent UV magnitudes. The C-IV 1549 angstrom and C III] 1909 angstrom lines of galaxies brighter than 26 AB magnitudes are detectable with current facilities such as the Very Large Telescope (VLT) XShooter and the Keck Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE). Metal lines such as C-IV 1549 angstrom, C III] 1909 angstrom, [O II] 3727 angstrom and [O III] 4959/5007 angstrom are good targets for spectroscopic observation with the Thirty-Metre Telescope (TMT), European Extremely Large Telescope (E-ELT), Giant Magellan Telescope (GMT) and James Webb Space Telescope (JWST). We also expect Ha and H beta lines to be detectable with these telescopes. Additionally, we predict the detectability of nebular lines for z &gt; 10 galaxies, which will be found with JWST, the Wide-Field Infrared Survey Telescope (WFIRST) and First Light And Reionization Explorer (FLARE) (11 &lt;= z &lt;= 15). We conclude that the C-IV 1549 angstrom, C III] 1909 angstrom, [O III] 4959/5007 angstrom and H beta lines from even z similar to 15 galaxies could be strong targets for TMT, E-ELT and JWST. We also find that magnification by gravitational lensing is of great help in detecting such high-z galaxies. According to our model, the C III] 1909 angstrom line in z &gt; 9 galaxy candidates is detectable even using current facilities.

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  • CONSTRAINING THE MOVEMENT OF THE SPIRAL FEATURES AND THE LOCATIONS OF PLANETARY BODIES WITHIN THE AB AUR SYSTEM

    Jamie R. Lomax, John P. Wisniewski, Carol A. Grady, Michael W. McElwain, Jun Hashimoto, Tomoyuki Kudo, Nobuhiko Kusakabe, Yoshiko K. Okamoto, Misato Fukagawa, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph C. Carson, Thayne M. Currie, Sebastian Egner, Markus Feldt, Miwa Goto, Olivier Guyon, Yutaka Hayano, Masahiko Hayashi, Saeko S. Hayashi, Thomas Henning, Klaus W. Hodapp, Akio Inoue, Miki Ishii, Masanori Iye, Markus Janson, Ryo Kandori, Gillian R. Knapp, Masayuki Kuzuhara, Jungmi Kwon, Taro Matsuo, Satoshi Mayama, Shoken Miyama, Munetake Momose, Jun-Ichi Morino, Amaya Moro-Martin, Tetsuo Nishimura, Tae-Soo Pyo, Glenn H. Schneider, Eugene Serabyn, Michael L. Sitko, Takuya Suenaga, Hiroshi Suto, Ryuji Suzuki, Yasuhiro H. Takahashi, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda, Motohide Tamura

    ASTROPHYSICAL JOURNAL   828 ( 1 )  2016.09

     View Summary

    We present a new analysis of multi-epoch, H-band, scattered light images of the AB Aur system. We use a Monte Carlo radiative transfer code to simultaneously model the system's spectral energy distribution (SED) and H-band polarized intensity (PI) imagery. We find that a disk-dominated model, as opposed to one that is envelope-dominated, can plausibly reproduce AB Aur's SED and near-IR imagery. This is consistent with previous modeling attempts presented in the literature and supports the idea that at least a subset of AB Aur's spirals originate within the disk. In light of this, we also analyzed the movement of spiral structures in multi-epoch H-band total light and PI imagery of the disk. We detect no significant rotation or change in spatial location of the spiral structures in these data, which span a 5.8-year baseline. If such structures are caused by disk-planet interactions, the lack of observed rotation constrains the location of the orbit of planetary perturbers to be >47 au.

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    5
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  • WATER ICE AT THE SURFACE OF THE HD 100546 DISK

    M. Honda, T. Kudo, S. Takatsuki, A. K. Inoue, T. Nakamoto, M. Fukagawa, M. Tamura, H. Terada, N. Takato

    ASTROPHYSICAL JOURNAL   821 ( 1 ) article id. 2 6 pp.  2016.04  [Refereed]

     View Summary

    We made near-infrared multicolor imaging observations of a disk around Herbig Be star HD. 100546 using Gemini/NICI. K (2.2 mu m), H2O ice (3.06 mu m), and L' (3.8 mu m) disk images were obtained and we found a 3.1 mu m absorption feature in the scattered light spectrum, likely due to water ice grains at the disk surface. We compared the observed depth of the ice absorption feature with the disk model based on Oka et al., including the water ice photodesorption effect by stellar UV photons. The observed absorption depth can be explained by both the disk models with and without the photodesorption effect within the measurement accuracy, but the model with photodesorption effects is slightly more favored, implying that the UV photons play an important role in the survival/destruction of ice grains at the Herbig Ae/Be disk surface. Further improvement to the accuracy of the observations of the water ice absorption depth is needed to constrain the disk models.

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    20
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  • Japanese Cosmic Dawn/Epoch of Reionization Science with the Square Kilometre Array

    Kenji Hasegawa, Shinsuke Asaba, Kiyotomo Ichiki, Akio K. Inoue, Susumu Inoue, Tomoaki Ishiyama, Hayato Shimabukuro, Keitaro Takahashi, Hiroyuki Tashiro, Hidenobu Yajima, Shu-ichiro Yokoyama, Kohji Yoshikawa, Shintaro Yoshiura, on behalf of Japan, SKA consortium, EoR Science Working Group

       2016.03

     View Summary

    Cosmic reionization is known to be a major phase transition of the gas in the<br />
    Universe. Since astronomical objects formed in the early Universe, such as the<br />
    first stars, galaxies and black holes, are expected to have caused cosmic<br />
    reionization, the formation history and properties of such objects are closely<br />
    related to the reionization process. In spite of the importance of exploring<br />
    reionization, our understandings regarding reionization is not sufficient yet.<br />
    Square Kilometre Array (SKA) is a next-generation large telescope that will be<br />
    operated in the next decade. Although several programs of next-generation<br />
    telescopes are currently scheduled, the SKA will be the unique telescope with a<br />
    potential to directly observe neutral hydrogen up to z~30, and provide us with<br />
    valuable information on the Cosmic Dawn (CD) and the Epoch of Reionization<br />
    (EoR). The early science with the SKA will start in a few years; it is thus the<br />
    time for us to elaborate a strategy for CD/EoR Science with the SKA. The<br />
    purpose of this document is to introduce Japanese scientific interests in the<br />
    SKA project and to report results of our investigation.

  • DISCOVERY OF A DAMPED Ly alpha ABSORBER AT z=3.3 ALONG A GALAXY SIGHT-LINE IN THE SSA22 FIELD

    K. Mawatari, A. K. Inoue, K. Kousai, T. Hayashino, R. Cooke, J. X. Prochaska, T. Yamada, Y. Matsuda

    ASTROPHYSICAL JOURNAL   817 ( 2 ) article id. 161, 7 pp.  2016.02  [Refereed]

     View Summary

    Using galaxies as background light sources to map the Ly alpha absorption lines is a novel approach to study Damped Ly alpha Absorbers (DLAs). We report the discovery of an intervening z = 3.335 +/- 0.007 DLA along a galaxy sight-line identified among 80 Lyman Break Galaxy (LBG) spectra obtained with our Very Large Telescope/Visible Multi-Object Spectrograph survey in the SSA22 field. The measured DLA neutral hydrogen (H-I) column density is log(N-H I/cm(-2)) = 21.68 +/- 0.17. The DLA covering fraction over the extended background LBG is &gt;70% (2 sigma), yielding a conservative constraint on the DLA area of greater than or similar to 1 kpc(2). Our search for a counterpart galaxy hosting this DLA concludes that there is no counterpart galaxy with star formation rate larger than a few M-circle dot yr(-1), ruling out an unobscured violent star formation in the DLA gas cloud. We also rule out the possibility that the host galaxy of the DLA is a passive galaxy with M-* greater than or similar to 5 x 10(10) M-circle dot or a heavily dust-obscured galaxy with E(B - V) greater than or similar to 2. The DLA may coincide with a large-scale overdensity of the spectroscopic LBGs. The occurrence rate of the DLA is compatible with that of DLAs found in QSO sight-lines.

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  • The critical radiation intensity for direct collapse black hole formation: dependence on the radiation spectral shape (vol 445, pg 544, 2014)

    Kazuyuki Sugimura, Kazuyuki Omukai, Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   452 ( 2 ) 1201 - 1201  2015.09

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  • Primordial star clusters at extreme magnification

    Erik Zackrisson, Juan Gonzalez, Simon Eriksson, Saghar Asadi, Chalence Safranek-Shrader, Michele Trenti, Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   449 ( 3 ) 3057 - 3063  2015.05  [Refereed]

     View Summary

    Gravitationally lensed galaxies with magnification mu approximate to 10-100 are routinely detected at high redshifts, but magnifications significantly higher than this are hampered by a combination of low probability and large source sizes. Magnifications of mu similar to 1000 may none the less be relevant in the case of intrinsically small, high-redshift objects with very high number densities. Here, we explore the prospects of detecting compact (less than or similar to 10 pc), high-redshift (z greater than or similar to 7) Population III star clusters at such extreme magnifications in large-area surveys with planned telescopes like Euclid, Wide Field Infrared Survey Telescope and Wide-field Imaging Surveyor for High-redshift (WISH). We find that the planned WISH 100 deg(2) ultradeep survey may be able to detect a small number of such objects, provided that the total stellar mass of these star clusters is greater than or similar to 10(4) M-circle dot. If candidates for such lensed Population III star clusters are found, follow-up spectroscopy of the surrounding nebula with the James Webb Space Telescope or ground-based Extremely Large Telescopes should be able to confirm the Population III nature of these objects. Multiband photometry of these objects with the James Webb Space Telescope also has the potential to confirm that the stellar initial mass function in these Population III star clusters is top-heavy, as supported by current simulations.

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    21
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  • Peering through the holes: the far-UV color of star-forming galaxies at z similar to 3-4 and the escaping fraction of ionizing radiation

    E. Vanzella, S. de Barros, M. Castellano, A. Grazian, A. K. Inoue, D. Schaerer, L. Guaita, G. Zamorani, M. Giavalisco, B. Siana, L. Pentericci, E. Giallongo, A. Fontana, C. Vignali

    ASTRONOMY & ASTROPHYSICS   576   id.A116, 13 pp.  2015.04  [Refereed]

     View Summary

    Aims. We aim to investigate the effect of the escaping ionizing radiation on the color selection of high-redshift galaxies and identify candidate Lyman-continuum (LyC) emitters.
    Methods. We used the intergalactic medium (IGM) prescription of Inoue et al. (2014, MNRAS, 442, 1805) and galaxy synthesis models of Bruzual & Charlot (2003, MNRAS, 344, 1000) to properly treat the ultraviolet stellar emission and the stochasticity of the intergalactic transmission and mean free path in the ionizing regime. Color tracks were computed by turning the escape fraction fesc of ionizing radiation on or off.
    Results. At variance with recent studies, a careful treatment of IGM transmission leads to no significant effects on the high-redshift broad-band color selection, even adopting the most extreme ionizing emission model (with an age of 1 Myr, zero dust, and metallicity Z/Z(circle dot) = 0.02). The decreasing mean free path of ionizing photons with increasing redshift further diminishes the contribution of the LyC to broad-band colors. We demonstrate that prominent LyC sources can be selected under suitable conditions by calculating the probability of a null escaping ionizing radiation. This was performed by running ad hoc Monte Carlo simulations anchored to the observed photometry, exploring the stochasticity of the IGM, and comparing the simulated and observed colors that encompass the Lyman edge. The method was applied to a sample of galaxies extracted from the GOODS-S field. A known LyC source at z = 3.795 was successfully recovered as a LyC-emitter candidate, and another convincing candidate at z = 3.212 is reported. A detailed analysis of the two sources (including their variability and morphology) suggests a possible mixture of stellar and non-stellar (AGN) contribution in the ultraviolet.
    Conclusions. The classical broad-band color selection of 2.5 &lt; z &lt; 4.5 galaxies does not prevent the inclusion of LyC emitters in the selected samples. High fesc in relatively bright galaxies (L &gt; 0.1L(star)) could be favored by the presence of a faint active galactic nucleus (AGN) that is not easily detected at any wavelength. A hybrid stellar and non-stellar (AGN) ionizing emission could coexist in these systems and explain the tensions found among the UV excess and the stellar population synthesis models reported in literature.

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  • The environments of Ly alpha blobs - I. Wide-field Ly alpha imaging of TN J1338-1942, a powerful radio galaxy at z similar or equal to 4.1 associated with a giant Ly alpha nebula

    Tomoki Saito, Yuichi Matsuda, Cedric G. Lacey, Ian Smail, Alvaro Orsi, Carlton M. Baugh, Akio K. Inoue, Ichi Tanaka, Toru Yamada, Kouji Ohta, Carlos De Breuck, Tadayuki Kodama, Yoshiaki Taniguchi

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   447 ( 4 ) 3069 - 3086  2015.03  [Refereed]

     View Summary

    We exploit wide-field Ly alpha imaging with Subaru to probe the environment around TN J1338-1942, a powerful radio galaxy with a &gt; 100 kpc Ly alpha halo at z = 4.11. We used a sample of Ly alpha emitters (LAEs) down to log (L-Ly alpha [erg s(-1)]) similar to 42.8 to measure the galaxy density around TN J1338-1942, compared to a control sample from a blank field taken with the same instrument. We found that TN J1338-1942 resides in a region with a peak over-density of delta(LAE) = 2.8 +/- 0.5 on scales of 8 h(-1) Mpc (on the sky) and 112 h(-1) Mpc (line of sight) in comoving coordinates. Adjacent to this overdensity, we found a strong underdensity where virtually no LAEs are detected. We used a semi-analytical model of LAEs derived from the Millennium Simulation to compare our results with theoretical predictions. While the theoretical density distribution is consistent with the blank field, overdense regions such as that around TN J1338-1942 are very rare, with a number density of 6.4 x 10(-8) Mpc(-3) (comoving), corresponding to the densest &lt; 0.4 percentile at z similar or equal to 4.1. We also found that the Ly alpha luminosity function in the TN J1338-1942 field differs from that in the blank field: the number of bright LAEs (log(L-Ly alpha [ergs(-1)]) greater than or similar to 43.3) is enhanced, while the number of fainter LAEs is relatively suppressed. These results suggest that some powerful radio galaxies associated with Ly a nebulae reside in extreme overdensities on similar to 3-6 Mpc scales, where star formation and AGN activity may be enhanced via frequent galaxy mergers or high rates of gas accretion from the surroundings.

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  • VARIABILITY OF DISK EMISSION IN PRE-MAIN SEQUENCE AND RELATED STARS. III. EXPLORING STRUCTURAL CHANGES IN THE PRE-TRANSITIONAL DISK IN HD 169142

    Kevin R. Wagner, Michael L. Sitko, Carol A. Grady, Jeremy R. Swearingen, Elizabeth H. Champney, Alexa N. Johnson, Chelsea Werren, Barbara A. Whitney, Ray W. Russell, Glenn H. Schneider, Munetake Momose, Takayuki Muto, Akio K. Inoue, James T. Lauroesch, Jeremy Hornbeck, Alexander Brown, Misato Fukagawa, Thayne M. Currie, John P. Wisniewski, Bruce E. Woodgate

    ASTROPHYSICAL JOURNAL   798 ( 2 ) article id. 94, 15 pp.  2015.01  [Refereed]

     View Summary

    We present near-IR (NIR) and far-UV observations of the pre-transitional (gapped) disk in HD 169142 using NASA's Infrared Telescope Facility and Hubble Space Telescope. The combination of our data along with existing data sets into the broadband spectral energy distribution reveals variability of up to 45% between similar to 1.5-10 mu m over a maximum timescale of 10 yr. All observations known to us separate into two distinct states corresponding to a high near-IR state in the pre-2000 epoch and a low state in the post-2000 epoch, indicating activity within the less than or similar to 1AU region of the disk. Through analysis of the Pa beta and Br gamma lines in our data we derive a mass accretion rate in 2013 May of (M)overdot approximate to (1.5-2.7) x 10-9 M-circle dot yr(-1). We present a theoretical modeling analysis of the disk in HD 169142 using Monte-Carlo radiative transfer simulation software to explore the conditions and perhaps signs of planetary formation in our collection of 24 yr of observations. We find that shifting the outer edge (r approximate to 0.3AU) of the inner disk by 0.05 AU toward the star (in simulation of accretion and/or sculpting by forming planets) successfully reproduces the shift in NIR flux. We establish that the similar to 40-70 AU dark ring imaged in the NIR by Quanz et al. and Momose et al. and at 7 mm by Osorio et al. may be reproduced with a 30% scaled density profile throughout the region, strengthening the link to this structure being dynamically cleared by one or more planetary mass bodies.

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    22
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  • The critical radiation intensity for direct collapse black hole formation: dependence on the radiation spectral shape

    Kazuyuki Sugimura, Kazuyuki Omukai, Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   445 ( 1 ) 544 - 553  2014.11  [Refereed]

     View Summary

    It has been proposed that supermassive black holes (SMBHs) are originated from direct-collapse black holes (DCBHs) that are formed at z greater than or similar to 10 in the primordial gas in the case where H-2 cooling is suppressed by strong external radiation. In this work, we study the critical specific intensity J(crit) required for DCBH formation for various radiation spectral shapes by a series of one-zone calculations of a collapsing primordial-gas cloud. We calculate the critical specific intensity at the Lyman-Werner (LW) bands J(LW,21)(crit) (in units of 10(-21) erg s(-1) Hz(-1) sr(-1) cm(-2)) for realistic spectra of metal-poor galaxies. We find that J(crit) is not sensitive to the age or metallicity for the constant star formation galaxies with J(LW,21)(crit) = 1300-1400, while J(crit) decreases as galaxies become older or more metal-enriched for the instantaneous starburst galaxies. However, for the young (the age &lt; 100 Myr) and/or extremely metal poor (Z &lt; 5 x 10(-4) Z(circle dot)) instantaneous starburst galaxies, such dependence is not strong and J(LW,21)(crit) = 1000-1400. We also find that J(crit) is solely determined by the ratio between the H- and H-2 photodissociation rate coefficients, k(H-,pd)/k(H2,pd), with which we develop a formula to estimate J(crit) for a given spectrum. The higher value of J(crit) for the realistic spectra than those expected in the literature significantly reduces the estimated DCBH number density n(DCBH). By extrapolating the result of Dijkstra, Ferrara & Mesinger, we obtain n(DCBH) similar to 10(-10) cMpc(-3) at z = 10, which is roughly consistent with the observed number density of high-redshift SMBHs n(SMBH) similar to 10(-9) cMpc(-3) at z similar to 6, considering large uncertainties in the estimation.

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    109
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  • Physical properties of UDF12 galaxies in cosmological simulations

    Ikkoh Shimizu, Akio K. Inoue, Takashi Okamoto, Naoki Yoshida

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   440 ( 1 ) 731 - 745  2014.05  [Refereed]

     View Summary

    We have performed a large cosmological hydrodynamics simulation tailored to the deep survey with the Hubble Space Telescope made in 2012, the so-called UDF12 campaign. After making a light-cone output, we have applied the same colour-selection criteria as the UDF12 campaign to select galaxies from our simulation, and then, have examined the physical properties of them as a proxy of the real observed UDF12 galaxies at z &gt; 7. As a result, we find that the halo mass is almost linearly proportional to the observed ultraviolet (UV) luminosity (4 x 10(11)M(circle dot) at M-UV = -21). The dust attenuation and UV slope beta well correlates with the observed UV luminosity, which is consistent with observations quantitatively. The star formation rate (SFR) is also linearly proportional to the stellar mass and the specific SFR shows only a weak dependence on the mass. We also find an increasing star formation history with a time-scale of similar to 100 Myr in the high-z galaxies. An average metallicity weighted by the Lyman continuum luminosity reaches up to &gt; 0.1 Solar even at z similar to 10, suggesting a rapid metal enrichment. We also expect &gt;= 0.1 mJy at 350 GHz of the dust thermal emission from the galaxies with H-160 &lt; 27, which can be detectable with the Atacama Large Millimetre-sub-millimetre Array. The galaxies selected by the UDF12 survey contribute to only 52-12 per cent of the cosmic SFR density from z similar to 7 to z similar to 10, respectively. The James Webb Space Telescope will push the detection fraction up to 77-72 per cent.

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    31
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  • THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. II. SPECTRAL SIGNATURES OF LYMAN CONTINUUM LEAKAGE FROM GALAXIES IN THE REIONIZATION EPOCH

    Erik Zackrisson, Akio K. Inoue, Hannes Jensen

    ASTROPHYSICAL JOURNAL   777 ( 1 ) article id. 39, 12 pp.  2013.11  [Refereed]

     View Summary

    The fraction of ionizing photons that escape (f(esc)) from z greater than or similar to 6 galaxies is an important parameter for assessing the role of these objects in the reionization of the universe, but the opacity of the intergalactic medium precludes a direct measurement of f(esc) for individual galaxies at these epochs. We argue that since f(esc) regulates the impact of nebular emission on the spectra of galaxies, it should nonetheless be possible to indirectly probe f(esc) well into the reionization epoch. As a first step, we demonstrate that by combining measurements of the rest-frame UV slope beta with the equivalent width of the H beta emission line, galaxies with very high Lyman continuum escape fractions (f(esc) &gt;= 0.5) should be identifiable up to z approximate to 9 through spectroscopy with the upcoming James Webb Space Telescope (JWST). By targeting strongly lensed galaxies behind low-redshift galaxy clusters, JWST spectra of sufficiently good quality can be obtained for M-1500 less than or similar to -16.0 galaxies at z approximate to 7 and for M-1500 less than or similar to -17.5 galaxies at z approximate to 9. Dust-obscured star formation may complicate the analysis, but supporting observations with ALMA or the planned SPICA mission may provide useful constraints on this effect.

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    94
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  • Effect of the Remnant Mass in Estimating the Stellar Mass of Galaxies

    Shimizu, I, Inoue, A. K

    Publications of the Astronomical Society of Japan   65 ( 5 ) Article No.96 8 pp.  2013.10  [Refereed]

     View Summary

    銀河の恒星質量分布関数は、近傍から遠方宇宙まで観測が進められており、銀河形成進化モデルと比較することで、モデルの標準的なテストとして用いられている。しかし、観測から導出した恒星質量と、モデルの恒星質量の定義が異なる場合が多々ある。この論文では、白色矮星など恒星の残骸の質量を含めるか否かでモデル恒星質量関数がどれほど異なるか検討し、場合によっては無視できない違いが現れることを指摘した。

    DOI

  • A GRAVITATIONAL LENS MODEL FOR THE Ly alpha EMITTER LAE 221724+001716 AT z=3.1 IN THE SSA 22 FIELD

    Y. Nakahiro, Y. Taniguchi, A. K. Inoue, Y. Shioya, M. Kajisawa, M. A. R. Kobayashi, I. Iwata, Y. Matsuda, T. Hayashino, A. R. Tanaka, K. Hamada

    ASTROPHYSICAL JOURNAL   766 ( 2 ) article id. 122, 5 pp.  2013.04  [Refereed]

     View Summary

    During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Ly alpha emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission (lambda(rest) similar to 900 angstrom) that escapes from this galaxy. However, another recent spectroscopic survey revealed that the supposed Lyman continuum emission could arise from a foreground galaxy at z = 1.76 if the emission line newly detected from the galaxy at lambda(obs) approximate to 3360 angstrom is Lya. If this is the case, as the angular separation between these two galaxies is very small (approximate to 0 ''. 6), LAE 221724+001716 at z = 3.10 could be amplified by the gravitational lensing caused by this intervening galaxy. Here we present a possible gravitational lens model for the system of LAE 221724+001716. First, we estimate the stellar mass of the intervening galaxy as M-star similar to 3.5 x 10(9) M-circle dot from its UV luminosity and similar to 3.0 x 10(7)-2.4 x 10(9) M-circle dot through the spectral energy distribution fitting. Then, we find that the gravitational magnification factor ranges from 1.01 to 1.16 using the so-called singular isothermal sphere model for strong lensing. While LAE 221724+001716 is the first system of an LAE-LAE lensing reported so far, the estimated magnification factor is not so significant because the stellar mass of the intervening galaxy is small.

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  • REVISITING THE COSMIC STAR FORMATION HISTORY: CAUTION ON THE UNCERTAINTIES IN DUST CORRECTION AND STAR FORMATION RATE CONVERSION

    Masakazu A. R. Kobayashi, Yoshiyuki Inoue, Akio K. Inoue

    ASTROPHYSICAL JOURNAL   763 ( 1 ) article id. 3, 12 pp.  2013.01  [Refereed]

     View Summary

    The cosmic star formation rate density (CSFRD) has been observationally investigated out to redshift z similar or equal to 10. However, most of the theoretical models for galaxy formation underpredict the CSFRD at z greater than or similar to 1. Since the theoretical models reproduce the observed luminosity functions (LFs), luminosity densities (LDs), and stellar mass density at each redshift, this inconsistency does not simply imply that theoretical models should incorporate some missing unknown physical processes in galaxy formation. Here, we examine the cause of this inconsistency at UV wavelengths by using a mock catalog of galaxies generated by a semi-analytic model of galaxy formation. We find that this inconsistency is due to two observational uncertainties: the dust obscuration correction and the conversion from UV luminosity to star formation rate (SFR). The methods for correction of obscuration and SFR conversion used in observational studies result in the overestimation of the CSFRD by similar to 0.1-0.3 dex and similar to 0.1-0.2 dex, respectively, compared to the results obtained directly from our mock catalog. We present new empirical calibrations for dust attenuation and conversion from observed UV LFs and LDs into the CSFRD.

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    18
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  • Dust formation history of galaxies: A critical role of metallicity for the dust mass growth by accreting materials in the interstellar medium

    Ryosuke S. Asano, Tsutomu T. Takeuchi, Hiroyuki Hirashita, Akio K. Inoue

    EARTH PLANETS AND SPACE   65 ( 3 ) 213 - 222  2013  [Refereed]

     View Summary

    This paper investigates the main driver of dust mass growth in the interstellar medium (ISM) by using a chemical evolution model of a galaxy with metals (elements heavier than helium) in the dust phase, in addition to the total amount of metals. We consider asymptotic giant branch (AGB) stars, type II supernovae (SNe II), and dust mass growth in the ISM, as the sources of dust, and SN shocks as the destruction mechanism of dust. Furthermore, to describe the dust evolution precisely, our model takes into account the age and metallicity (the ratio of metal mass to ISM mass) dependence of the sources of dust. We have particularly focused on the dust mass growth, and found that in the ISM this is regulated by the metallicity. To quantify this aspect, we introduce a "critical metallicity", which is the metallicity at which the contribution of stars (AGB stars and SNe II) equals that of the dust mass growth in the ISM. If the star-formation timescale is shorter, the value of the critical metallicity is higher, but the galactic age at which the metallicity reaches the critical metallicity is shorter. From observations, it was expected that the dust mass growth was the dominant source of dust in the Milky Way and dusty QSOs at high redshifts. By introducing a critical metallicity, it is clearly shown that the dust mass growth is the main source of dust in such galaxies with various star-formation timescales and ages. The dust mass growth in the ISM is regulated by metallicity, and we emphasize that the critical metallicity serves as an indicator to judge whether the grain growth in the ISM is the dominant source of dust in a galaxy, especially because of the strong, and nonlinear, dependence on the metallicity.

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    158
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  • REEXAMINATION OF THE INFRARED EXCESS-ULTRAVIOLET SLOPE RELATION OF LOCAL GALAXIES

    Tsutomu T. Takeuchi, Fang-Ting Yuan, Akira Ikeyama, Katsuhiro L. Murata, Akio K. Inoue

    ASTROPHYSICAL JOURNAL   755 ( 2 ) article id. 144, 16pp.  2012.08  [Refereed]

     View Summary

    The relation between the ratio of infrared (IR) and ultraviolet (UV) flux densities (the infrared excess: IRX) and the slope of the UV spectrum (beta) of galaxies plays a fundamental role in the evaluation of the dust attenuation of star-forming galaxies, especially at high redshifts. Many authors, however, have pointed out that there is a significant dispersion and/or deviation from the originally proposed IRX-beta relation depending on sample selection. We reexamined the IRX-beta relation by measuring the far-and near-UV flux densities of the original sample galaxies with GALEX and AKARI imaging data and constructed a revised formula. We found that the newly obtained IRX values were lower than the original relation because of the significant underestimation of the UV flux densities of the galaxies, caused by the small aperture of IUE. Furthermore, since the original relation was based on IRAS data that covered a wavelength range of lambda = 42-122 mu m, we obtained an appropriate IRX-beta relation with total dust emission (TIR): log(L-TIR/L-FUV) = log[10(0.4(3.06+1.58 beta)) - 1] + 0.22 using the data from AKARI, which has wider wavelength coverage toward longer wavelengths. This new relation is consistent with most of the preceding results for samples selected at optical and UV, though there is significant scatter around it. We also found that even the quiescent class of IR galaxies follows this new relation, though luminous and ultraluminous IR galaxies distribute completely differently as previously thought.

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    74
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  • EFFECT OF PHOTODESORPTION ON THE SNOW LINES AT THE SURFACE OF OPTICALLY THICK CIRCUMSTELLAR DISKS AROUND HERBIG Ae/Be STARS

    Akinori Oka, Akio K. Inoue, Taishi Nakamoto, Mitsuhiko Honda

    ASTROPHYSICAL JOURNAL   747 ( 2 ) Article id. 138  2012.03  [Refereed]

     View Summary

    We investigate the effect of photodesorption on the snow line position at the surface of a protoplanetary disk around a Herbig Ae/Be star, motivated by the detection of water ice particles at the surface of the disk around HD142527 by Honda et al. For this aim, we obtain the density and temperature structure in the disk with a 1+1D radiative transfer and determine the distribution of water ice particles in the disk by the balance between condensation, sublimation, and photodesorption. We find that photodesorption induced by far-ultraviolet radiation from the central star depresses the ice-condensation front toward the mid-plane and pushes the surface snow line significantly outward when the stellar effective temperature exceeds a certain critical value. This critical effective temperature depends on the stellar luminosity and mass, the water abundance in the disk, and the yield of photodesorption. We present an approximate analytic formula for the critical temperature. We separate Herbig Ae/Be stars into two groups on the HR diagram according to the critical temperature: one is the disks where photodesorption is effective and from which we may not find ice particles at the surface, and the other is the disks where photodesorption is not effective. We estimate the snow line position at the surface of the disk around HD142527 to be 100-300 AU, which is consistent with the water ice detection at &gt;140 AU in the disk. All the results depend on the dust grain size in a complex way, and this point requires more work in the future.

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    12
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  • The Hubble Space Telescope colours of high-redshift Population III galaxies with strong Lya emission

    Erik Zackrisson, Akio K. Inoue, Claes-Erik Rydberg, Florent Duval

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   418 ( 1 ) L104 - L108  2011.11  [Refereed]

     View Summary

    Population III (pop III) galaxies, made partly or exclusively of metal-free stars, are predicted to exist at high redshifts and may produce very strong Lya emission. A substantial fraction of these Lya photons are likely absorbed in the intergalactic medium at z &gt; 6, but recent simulations suggest that significant Lya emission may be detectable up to z similar to 8.5, i.e. well into the reionization epoch. Here, we argue that high-redshift pop III galaxies with strong Lya emission can be identified in Hubble Space Telescope imaging data because of their unusual colours. We quantify this effect in some of the filters used in Y-band dropout searches for galaxies at z approximate to 8 and find that pop III galaxies with high Lya fluxes may exhibit much bluer J-H colours at z approximate to 8-10 than any normal type of galaxy at these redshifts. This colour signature can arise even if pop III stars account for as little as similar to 10(-3) to 10(-2) of the stellar mass in these galaxies. Some of the anomalously blue objects reported in current Y-band dropout samples do in fact meet the colour criteria for Lya-emitting pop III galaxies.

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    13
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  • Ly alpha emitters at z=6.5 in the SSA22 field: an area more neutral or void at the end of the re-ionization epoch

    E. Nakamura, A. K. Inoue, T. Hayashino, M. Horie, K. Kousai, T. Fujii, Y. Matsuda

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   412 ( 4 ) 2579 - 2586  2011.04  [Refereed]

     View Summary

    We present results of a survey of Ly alpha emitters (LAEs) at z = 6.5 which is thought to be the final epoch of the cosmic re-ionization. In a approximate to 530 arcmin2 deep image of the SSA22 field taken through a narrow-band filter NB912 installed in the Subaru/Suprime-Cam, we have found only 14 LAE candidates with L-Ly alpha greater than or similar to 3 x 1042 erg s-1. Even applying the same colour selection criteria, the number density of the LAE candidates is a factor of 3 smaller than that found at the same redshift in the Subaru Deep Field (SDF). Assuming the number density in the SDF is a cosmic average, the probability to have a number density equal to or smaller than that found in the SSA22 field is only 7 per cent if we consider fluctuation by the large-scale structure (i.e. cosmic variance) and Poisson error. Therefore, the SSA22 field may be a rare void at z = 6.5. On the other hand, we have found that the number density of i'-drop galaxies with 25.5 &lt; z' &lt; 26.0 in the SSA22 field agrees well with that in the SDF. If we consider a scenario that a larger neutral fraction of intergalactic hydrogen, x(H I), in the SSA22 field obscures a part of Ly alpha emission, x(H I) in the SSA22 field should be about two times larger than that in the SDF. This can be translated into x(H I) &lt; 0.9 at z = 6.5 in the SSA22 field. A much larger survey area than previous ones is required to overcome a large fluctuation reported here and to obtain a robust constraint on x(H I) at the end of the re-ionization from LAEs.

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    18
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  • Lyman 'bump' galaxies - II. A possible signature of massive extremely metal-poor or metal-free stars in z = 3.1 Ly alpha emitters

    A. K. Inoue, K. Kousai, I. Iwata, Y. Matsuda, E. Nakamura, M. Horie, T. Hayashino, C. Tapken, M. Akiyama, S. Noll, T. Yamada, D. Burgarella, Y. Nakamura

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   411 ( 4 ) 2336 - 2352  2011.03  [Refereed]

     View Summary

    Deep narrow-band (NB359) imaging with Subaru telescope by Iwata et al. has detected a surprisingly strong Lyman continuum (LyC; similar to 900 A in the rest frame) from some Lyman alpha emitters (LAEs) at z = 3.1. However, the possibility of a redshift misidentification by the previous spectroscopic studies due to a narrow wavelength coverage cannot be rejected. Here we present the results of a new technique, the deep spectroscopy, in which we covered 4000-7000 A with VLT/VIMOS and Subaru/FOCAS for the eight LAEs detected in NB359. All the eight objects have only one detectable emission line around 4970 A, which is most likely to be Ly alpha at z = 3.1, and thus, the objects are certainly LAEs at the redshift. However, five of them show a similar to 0.8 arcsec spatial offset between the Ly alpha emission and the source detected in NB359. No indications of the redshifts of the NB359 sources are found although it is statistically difficult that all the five LAEs have a foreground object accounting for the NB359 flux. The rest three LAEs show no significant offset from the NB359 position. Therefore, we conclude that they are truly LyC-emitting LAEs at z = 3.1. We also examine the stellar population which simultaneously accounts for the strength of the LyC and the spectral slope of non-ionizing ultraviolet of the LAEs. We consider the latest statistics of Lyman limit systems to estimate the LyC optical depth in the intergalactic medium (IGM) and an additional contribution of the bound-free LyC from photoionized nebulae to the LyC emissivity. As a result, we find that stellar populations with metallicity Z &gt;= 1/50 Z(circle dot) can explain the observed LyC strength only with a very top-heavy initial mass function (IMF; &lt;&lt; m &gt;&gt; similar to 50 M-circle dot). However, the critical metallicity for such an IMF is expected to be much lower. A very young (similar to 1 Myr) and massive (similar to 100 M-circle dot) extremely metal-poor (Z &lt; 5 x 10-4 Z(circle dot)) or metal-free (so-called Population III) stellar population can reproduce the observed LyC strength. The required mass fraction of such 'primordial' stellar population is similar to 1-10 per cent in total stellar mass of the LAEs. We also present a possible evolutionary scenario of galaxies emitting strong LyC and implications of the primordial stars at z similar to 3 for the metal enrichment in the intergalactic medium and for the ionizing background and reionization.

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    34
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  • THE GREAT OBSERVATORIES ORIGINS DEEP SURVEY: CONSTRAINTS ON THE LYMAN CONTINUUM ESCAPE FRACTION DISTRIBUTION OF LYMAN-BREAK GALAXIES AT 3.4 &lt; z &lt; 4.5

    E. Vanzella, M. Giavalisco, A. K. Inoue, M. Nonino, F. Fontanot, S. Cristiani, A. Grazian, M. Dickinson, D. Stern, P. Tozzi, E. Giallongo, H. Ferguson, H. Spinrad, K. Boutsia, A. Fontana, P. Rosati, L. Pentericci

    ASTROPHYSICAL JOURNAL   725 ( 1 ) 1011 - 1031  2010.12  [Refereed]

     View Summary

    We use ultra-deep ultraviolet VLT/VIMOS intermediate-band and VLT/FORS1 narrowband imaging in the GOODS Southern field to derive limits on the distribution of the escape fraction (f(esc)) of ionizing radiation for L &gt;= L-z=3* Lyman-break galaxies (LBGs) at redshift 3.4-4.5. Only one LBG, at redshift z = 3.795, is detected in its Lyman continuum (LyC; S/N similar or equal to 5.5), the highest redshift galaxy currently known with a direct detection. Its ultraviolet morphology is quite compact (R-eff = 0.8 kpc physical). Three out of seven active galactic nuclei are also detected in their LyC, including one at redshift z = 3.951 and z(850) = 26.1. From stacked data (LBGs), we set an upper limit to the average f(esc) in the range 5%-20%, depending on how the data are selected (e. g., by magnitude and/or redshift). We undertake extensive Monte Carlo simulations that take into account intergalactic attenuation, stellar population synthesis models, dust extinction, and photometric noise in order to explore the moments of the distribution of the escaping radiation. Various distributions (exponential, log-normal, and Gaussian) are explored. We find that the median f(esc) is lower than similar or equal to 6% with an 84% percentile limit not larger than 20%. If this result remains valid for fainter LBGs down to current observational limits, then the LBG population might be not sufficient to account for the entire photoionization budget at the redshifts considered here, with the exact details dependent upon the assumed ionizing background and QSO contribution thereto. It is possible that f(esc) depends on the UV luminosity of the galaxies, with fainter galaxies having higher f(esc), and estimates of f(esc) from a sample of faint LBGs from HUDF (i775 &lt;= 28.5) are in broad quantitative agreement with such a scenario.

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    125
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  • PRE-TRANSITIONAL DISK NATURE OF THE AB Aur DISK

    M. Honda, A. K. Inoue, Y. K. Okamoto, H. Kataza, M. Fukagawa, T. Yamashita, T. Fujiyoshi, M. Tamura, J. Hashimoto, T. Miyata, S. Sako, I. Sakon, H. Fujiwara, T. Kamizuka, T. Onaka

    ASTROPHYSICAL JOURNAL LETTERS   718 ( 2 ) L199 - L203  2010.08  [Refereed]

     View Summary

    The disk around AB Aur was imaged and resolved at 24.6 mu m using the Cooled Mid-infrared Camera and Spectrometer on the 8.2 m Subaru Telescope. The Gaussian full width at half-maximum of the source size is estimated to be 90 +/- 6 AU, indicating that the disk extends further out at 24.6 mu m than at shorter wavelengths. In order to interpret the extended 24.6 mu m image, we consider a disk with a reduced surface density within a boundary radius R(c), which is motivated by radio observations that suggest a reduced inner region within about 100 AU from the star. Introducing the surface density reduction factor f(c) for the inner disk, we determine that the best match with the observed radial intensity profile at 24.6 mu m is achieved with R(c) = 88 AU and f(c) = 0.01. We suggest that the extended emission at 24.6 mu m is due to the enhanced emission from a wall-like structure at the boundary radius (the inner edge of the outer disk), which is caused by a jump in the surface density at R(c). Such a reduced inner disk and geometrically thick outer disk structure can also explain the more point-like nature at shorter wavelengths. We also note that this disk geometry is qualitatively similar to a pre-transitional disk, suggesting that the AB Aur disk is in a pre-transitional disk phase.

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    16
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  • Lyman &apos;bump&apos; galaxies - I. Spectral energy distribution of galaxies with an escape of nebular Lyman continuum

    Akio K. Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   401 ( 2 ) 1325 - 1333  2010.01  [Refereed]

     View Summary

    It is essential to know galactic emissivity and spectrum of Lyman continuum (LyC) in order to understand the cosmic re-ionization. Here we consider an escape of nebular LyC from galaxies and examine the consequent spectral energy distribution. It is usually assumed that hydrogen nebular LyC mostly produced by bound-free transitions is consumed within photoionized nebulae (so-called on-the-spot approximation). However, an escape of the continuum should be taken into account if stellar LyC escapes from galaxies through &apos;matter-bounded&apos; nebulae. We show that the escaping hydrogen bound-free LyC makes a strong bump just below the Lyman limit. Such a galaxy would be observed as a Lyman &apos;bump&apos; galaxy. This bump results from the radiation energy redistribution of stellar LyC by nebulae. The strength of the bump depends on electron temperature in nebulae, escape fraction of stellar and nebular LyC, hardness of stellar LyC (i.e. metallicity, initial mass function, age and star formation history) and intergalactic medium attenuation. We can use the bump to find very young (similar to 1 Myr), massive (similar to 100 M(circle dot)) and extremely metal-poor (or metal-free) stellar populations at z &lt; 4. Because of the bump, 900-to-1500 A luminosity density ratio (per Hz) becomes maximum (two-three times larger than the stellar intrinsic ratio) when about 40 per cent of the stellar LyC is absorbed by nebulae. The total number of escaping LyC photons increases due to the escape of nebular LyC but does not exceed the stellar intrinsic one. The radiation energy redistribution by nebulae reduces the mean energy of escaping LyC only by approximate to 10 per cent relative to that of stellar LyC. Therefore, the effect of the escape of nebular LyC on the re-ionization process may be small.

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    32
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  • Intergalactic dust and its photoelectric heating

    Akio K. Inoue, Hideyuki Kamaya

    EARTH PLANETS AND SPACE   62 ( 1 ) 69 - 79  2010  [Refereed]

     View Summary

    We have examined dust photoelectric heating in the intergalactic medium (IGM). The heating rate in a typical radiation field of the IGM is represented by Gamma(pe) = 1.2 x 10(-34) erg s(-1) cm(-3) (D/10(-4))(n(H)/10(-5) cm(-3))(4/3)(J(L)/10(-21) erg s(-1) cm(-2) Hz(-1) sr(-1))(2/3)(T/10(4) K)(-1/6), where D is the dust-to-gas mass ratio, n(H) is the hydrogen number density, J(L) is the mean intensity at the hydrogen Lyman limit of the background radiation, and T is the gas temperature, if we assume the new X-ray photoelectric yield model by Weingartner et al. (2006) and the dust size distribution in the Milky Way by Mathis et al. (1977). This heating rate dominates the HI and Hell photoionization heating rates when the hydrogen number density is less than similar to 10(-6) cm(-3) if D = 10(-4) which is 1% of that in the Milky Way, although the heating rate is a factor of 2-4 smaller than that with the old yield model by Weingartner and Draine (2001). The grain size distribution is very important. If only large (&gt;= 0.1 mu m) grains exist in the IGM, the heating rate is reduced by it factor of similar or equal to 5. Since dust heating is more efficient in a lower density medium relative to the photoionization heating, it may Cause all inverted temperature-density relation in the low-density IGM, as Suggested by Bolton et al. (2008). Finally, we have found that dust heating is not very important in the mean IGM before the cosmic reionization.

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    7
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  • Ly alpha blobs like company: the discovery of a candidate 100 kpc Ly alpha blob near to a radio galaxy with a giant Ly alpha halo B3 J2330+3927 at z=3.1

    Y. Matsuda, Y. Nakamura, N. Morimoto, Ian Smail, C. De Breuck, K. Ohta, T. Kodama, A. K. Inoue, T. Hayashino, K. Kousai, E. Nakamura, M. Horie, T. Yamada, M. Kitamura, T. Saito, Y. Taniguchi, I. Tanaka, P. Hibon

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   400 ( 1 ) L66 - L70  2009.11  [Refereed]

     View Summary

    We present the discovery of a candidate of giant radio-quiet Ly alpha blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Ly alpha halo B3 J2330+3927 at redshift z = 3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Ly alpha emitters (LAEs) and absorbers (LAAs) at redshift z = 3.09 +/- 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 x 24 arcmin(2) (58 x 44 comoving Mpc). We found that B3 J2330+3927 is surrounded by a 130 kpc Ly alpha halo and a large-scale (similar to 60 x 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8 arcmin (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Ly alpha nebulae in the same large-scale structure suggests that giant Ly alpha nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Ly alpha nebulae. First, RQLAB may need a prominent (delta similar to 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Ly alpha halo around HzRG may not always need a prominent density peak to form if the surrounding Ly alpha halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Ly alpha halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey.

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    41
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  • Effects of scattering and dust grain size on the temperature structure of protoplanetary discs: a three-layer approach

    Akio K. Inoue, Akinori Oka, Taishi Nakamoto

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   393 ( 4 ) 1377 - 1390  2009.03

     View Summary

    The temperature in the optically thick interior of protoplanetary discs is essential for the interpretation of millimetre observations of the discs, for the vertical structure of the discs, for models of the disc evolution and the planet formation, and for the chemistry in the discs. Since large icy grains have a large albedo even in the infrared, the effect of scattering of the diffuse radiation in the discs on the interior temperature should be examined. We have performed a series of numerical radiation transfer simulations, including isotropic scattering by grains with various typical sizes for the diffuse radiation as well as for the incident stellar radiation. We also have developed an analytic model including isotropic scattering to understand the physics concealed in the numerical results. With the analytic model, we have shown that the standard two-layer approach is valid only for grey opacity (i.e. grain size greater than or similar to 10 mu m) even without scattering. A three-layer interpretation is required for grain size less than or similar to 10 mu m. When the grain size is 0.1-10 mu m, the numerical simulations show that the isotropic scattering reduces the temperature of the disc interior. This reduction is nicely explained by the analytic three-layer model as a result of the energy loss by scatterings of the incident stellar radiation and of the warm diffuse radiation in the disc atmosphere. For grain size greater than or similar to 10 mu m (i.e. grey scattering), the numerical simulations show that the isotropic scattering does not affect the interior temperature. This is nicely explained by the analytic two-layer model; the energy loss by scattering in the disc atmosphere is exactly offset by the &apos;green-house effect&apos; due to the scattering of the cold diffuse radiation in the interior.

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    10
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  • DETECTIONS OF LYMAN CONTINUUM FROM STAR-FORMING GALAXIES AT z similar to 3 THROUGH SUBARU/SUPRIME-CAM NARROW-BAND IMAGING

    I. Iwata, A. K. Inoue, Y. Matsuda, H. Furusawa, T. Hayashino, K. Kousai, M. Akiyama, T. Yamada, D. Burgarella, J. -M. Deharveng

    ASTROPHYSICAL JOURNAL   692 ( 2 ) 1287 - 1293  2009.02  [Refereed]

     View Summary

    Knowing the amount of ionizing photons from young star-forming galaxies is of particular importance to understanding the reionization process. Here we report initial results of a Subaru/Suprime-Cam deep imaging observation of the SSA22 proto-cluster region at z = 3.09, using a special narrow-band filter to optimally trace ionizing radiation from galaxies at z similar to 3. The unique wide field-of-view of Suprime-Cam enabled us to search for ionizing photons from 198 galaxies (73 Lyman break galaxies (LBGs) and 125 Ly alpha emitters (LAEs)) with spectroscopically measured redshifts z similar or equal to 3.1. We detected ionizing radiation from 7 LBGs, as well as from 10 LAE candidates. Some of the detected galaxies show significant spatial offsets of ionizing radiation from nonionizing UV emission. For some LBGs the observed nonionizing UV to Lyman continuum flux density ratios are smaller than values expected from population synthesis models with a standard Salpeter initialmass function (IMF) with moderate dust attenuation (which is suggested from the observed UV slopes), even if we assume very transparent intergalactic medium along the sightlines of these objects. This implies an intrinsically bluer spectral energy distribution, e. g., that produced by a top-heavy IMF, for these LBGs. The observed flux density ratios of nonionizing UV to ionizing radiation of 7 detected LBGs range from 2.4 to 23.8 and the median is 6.6. The observed flux density ratios of the detected LAEs are even smaller than LBGs, if they are truly at z similar or equal to 3.1. We find that the median value of the flux density ratio for the detected LBGs suggests that their escape fractions are likely to be higher than 4%, if the Lyman continuum escape is isotropic. The results imply that some of the LBGs in the proto-cluster at z similar to 3 have escape fraction significantly higher than that of galaxies (in a general field) at z similar to 1 studied previously.

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    164
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  • A Monte Carlo simulation of the intergalactic absorption and the detectability of the Lyman continuum from distant galaxies

    Akio K. Inoue, Ikuru Iwata

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   387 ( 4 ) 1681 - 1692  2008.07  [Refereed]

     View Summary

    We have made a Monte Carlo simulation of the intergalactic absorption in order to model the Lyman continuum absorption, which is required to estimate the escape fraction of the Lyman continuum from distant galaxies. To input into the simulation, we derive an empirical distribution function of the intergalactic absorbers which reproduces recent observational statistics of the Lyman alpha forest, Lyman limit systems (LLSs) and damped Lyman alpha systems (DLAs) simultaneously. In particular, we assume a common functional form of the number evolution along the redshift for all types of absorbers. The Lyman series transmissions in our simulation reproduce the observed redshift evolution of the transmissions excellently, and the Lyman continuum transmission also agrees with an observed estimation which is still quite rare in the literature. The probability distribution of the Lyman alpha opacity in our simulation is lognormal with a tail towards a large opacity. This tail is produced by DLAs. The probability distribution of the Lyman continuum opacity in our simulation also shows a broad tail towards a large opacity. This tail is produced by LLSs. Because of the rarity of LLSs, we have a chance to have a clean line of sight in the Lyman continuum even for z similar to 4 with a probability of about 20 per cent. Our simulation expects a good correlation between the Lyman continuum opacity and the Lyman alpha opacity, which may be useful to estimate the former from the latter for an individual line of sight.

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    81
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  • Observational possibility of the "snow line" on the surface of circumstellar disks with the scattered light

    Akio K. Inoue, Mitsuhiko Honda, Taishi Nakamoto, Akinori Oka

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   60 ( 3 ) 557 - 563  2008.06  [Refereed]

     View Summary

    We discuss how we obtain the spatial distribution of ice on the surface of the circumstellar disk around young stars. Ice in the disks plays a very important role in various issues, for instance, on the disk structure, on planet formation, on an isotopic anomaly in meteorites, and on the origin of the oceans on Earth. Therefore, spatially resolved observations of the condensation/sublimation front of ice, the so-called snow line is strongly required. Here, we propose a new method for obtaining a spatially resolved snow line on circumstellar disks by observing a 3 mu m H2O ice feature in the scattered light. Based on radiative transfer considerations, we show that the feature is clearly imprinted in the spectrum of the scattered light from both optically thick and thin circumstellar disks. We also show that the scattered light and the H2O ice feature from protoplanetary disks are detectable and spatially resolvable with current instruments through an H2O narrowband filter around 3 Am. Finally, we present a diagnostics of disk dust properties on K - H2O and K - L' two-color diagram.

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  • Ultraviolet dust attenuation in spiral galaxies: the role of age-dependent extinction and the initial mass function

    P. Panuzzo, G. L. Granato, V. Buat, A. K. Inoue, L. Silva, J. Iglesias-Paramo, A. Bressan

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   375 ( 2 ) 640 - 648  2007.02  [Refereed]

     View Summary

    We analyse the attenuation properties of a sample of ultraviolet (UV) selected galaxies, with the use of the spectrophotometric model GRASIL. In particular, we focus on the relation between dust attenuation and the reddening in the UV spectral region. We show that a realistic modelling of geometrical distribution of dust and the different population of stars can explain the UV reddening of normal spiral galaxies also with a standard Milky Way dust. Our results clearly underline that it is fundamental to take into account that younger stars suffer a higher attenuation than older stars (the age-dependent extinction) because stars are born in more-than-average dusty environments. In this work, we also find that the concentration of young stars on the galactic plane of spirals has a relevant impact on the expected UV colours, impact that has not been explored before this paper. Finally, we discuss the role of the initial mass function (IMF) in shaping the relation between UV reddening and dust attenuation, and we show that a Kroupa IMF is more consistent with observed data than the classical Salpeter IMF.

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    72
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  • Fragmentation of star-forming clouds enriched with the first dust

    R Schneider, K Omukai, AK Inoue, A Ferrara

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   369 ( 3 ) 1437 - 1444  2006.07  [Refereed]

     View Summary

    The thermal and fragmentation properties of star forming clouds have important consequences on the corresponding characteristic stellar mass. The initial composition of the gas within these clouds is a record of the nucleosynthetic products of previous stellar generations. In this paper, we present a model for the evolution of star forming clouds enriched by metals and dust from the first supernovae (SNe), resulting from the explosions of metal-free progenitors with masses in the range 12-30M(circle dot) and 140-260M(circle dot). Using a self-consistent approach, we show that: (i) metals depleted on to dust grains play a fundamental role, enabling fragmentation to solar or subsolar mass scales already at metallicities Z(cr) = 10(-6) Z(circle dot); (ii) even at metallicities as high as 10(-2) Z(circle dot), metals diffused in the gas phase lead to fragment mass scales which are greater than or similar to 100M(circle dot); (iii) C atoms are strongly depleted on to amorphous carbon grains and CO molecules so that CII plays a minor role in gas cooling, leaving OI as the main gas-phase cooling agent in low-metallicity clouds. These conclusions hold independently of the assumed SN progenitors and suggest that the onset of low-mass star formation is conditioned to the presence of dust in the parent clouds.

    DOI

  • Effects of dust scattering albedo and 2175-angstrom bump on ultraviolet colours of normal disc galaxies

    Akio K. Inoue, Veronique Buat, Denis Burgarella, Pasquale Panuzzo, Tsutomu T. Takeuchi, Jorge Iglesias-Paramo

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   370 ( 1 ) 380 - 398  2006.07  [Refereed]

     View Summary

    We discuss dust properties in the interstellar medium (ISM) of nearby normal galaxies by comparing observations in the ultraviolet (UV) with simulations by a radiative transfer model. The observed UV colours of nearby galaxies show a reddening relative to their expected intrinsic colours. Some authors argued that the Milky Way dust cannot reproduce the reddening because of the prominent 2175-angstrom absorption bump. Other authors proposed a reduction mechanism of the bump strength in an attenuation law derived from the ratio of the observed intensity to the intrinsic one through an age-selective attenuation (i.e. young stars are more attenuated selectively). We find that the wavelength dependence of the scattering albedo also has a strong effect on the UV colour; an albedo decreasing towards shorter wavelengths (except for the absorption bump range) produces a significant UV reddening. After comparing the observed UV colours of nearby normal galaxies with those expected from radiative transfer simulations assumed several dust models, we find two sorts of dust suitable for these galaxies: (i) dust with a bump and a smaller albedo for a shorter wavelength (except for the bump range) and (ii) dust without any bump but with an almost constant albedo. If very small carbonaceous grains responsible for the common unidentified infrared emission band are also the bump carrier, the former dust is favourable. Finally, we derive mean attenuation laws of various dust models as a function of the UV attenuation, and derive some relations between the UV attenuation and observable/theoretical quantities.

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    31
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  • Spectroscopy and stellar populations of star-forming galaxies at z similar to 3 in the Hubble Deep Field-South

    Iwata, I, AK Inoue, D Burgarella

    ASTRONOMY & ASTROPHYSICS   440 ( 3 ) 881 - 892  2005.09  [Refereed]

     View Summary

    We present results of VLT/FORS2 spectroscopy of galaxies at z similar to 3 in the Hubble Deep Field - South (HDF-S). A sample of galaxies was drawn from the photometric redshift catalogue based on the HST/WFPC2 optical images and the deep near-infrared images obtained with VLT/ISAAC as a part of the Faint Infrared Extragalactic Survey ( FIRES) project. We selected galaxies with photometric redshift between 2.5 and 4. Most of the selected galaxies are bright in rest-frame UV wavelengths and satisfy color selection criteria of Lyman break galaxies (LBGs) at z similar to 3. The number of target galaxies with I-AB &lt;= 25.0 was 15. We identified new 5 firm and 2 probable redshifts in addition to confirmation of 6 previously known galaxies at z similar to 3. We found that 6 among these 13 galaxies lie in a quite narrow redshift range at z = 2.80 +/- 0.01. Their spatial distribution is fairly concentrated and is at the edge of the HDF-S field, suggesting the possible existence of larger galaxy clustering. We examined stellar populations of the galaxies with spectroscopic redshifts through comparisons of their optical and near-infrared photometry data with template spectra generated by a population synthesis code. The ages from the onset of star formation for these star-forming galaxies with I &lt;= 25.0 are typically 50- 200 Myr, and their stellar masses are between (0.5- 5) x 10(10) M-., consistent with previous studies. We also compared these SED fitting results with those for "distant red galaxies" (DRGs) at z &gt; 2 discovered by FIRES. DRGs have larger stellar masses, higer dust attenuation than our UV-luminous LBG sample, and their star formation rates are often comparable to LBGs. These trends suggest that majority of the DRGs are indeed the most massive systems at that redshift and are still in the active star-forming phase. Unless the number density of DRGs is much smaller than LBGs, estimates based on a UV selected sample could miss substantial part of stellar mass density at z similar to 3.

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    14
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  • VLT narrow-band photometry in the Lyman continuum of two galaxies at z ∼ 3* limits to the escape of ionizing flux

    A. K. Inoue, I. Iwata, J. M. Deharveng, V. Buat, D. Burgarella

    Astronomy and Astrophysics   435 ( 2 ) 471 - 482  2005.05

     View Summary

    We have performed narrow-band imaging observations with the Very Large Telescope, aimed at detecting the Lyman continuum (LC) flux escaping from galaxies at z ∼ 3. We do not find any significant LC flux from our sample of two galaxies in the Hubble Deep Field South, at z = 3.170 and 3.275. The corresponding lower limits on the F1400/F900 flux density (per Hz) ratio are 15.6 and 10.2 (3-σ confidence level). After correction for the intergalactic hydrogen absorption, the resulting limits on the relative escape fraction of the LC are compared with those obtained by different approaches, at similar or lower redshifts. One of our two objects has a relative escape fraction lower than the detection reported by Steidel et al. in a composite spectrum of z ∼ 3 galaxies. A larger number of objects is required to reach a significant conclusion. Our comparison shows the potential of narrow-band imaging for obtaining the best limit on the relative escape fraction at z ∼ 3. Stacking a significant number of galaxies observed through a narrow-band filter would provide constraint on the galactic contribution to the cosmic reionization. © ESO 2005.

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    62
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  • VLT narrow-band photometry in the Lyman continuum of two galaxies at z similar to 3 - Limits to the escape of ionizing flux

    AK Inoue, Iwata, I, JM Deharveng, Buat, V, D Burgarella

    ASTRONOMY & ASTROPHYSICS   435 ( 2 ) 471 - 482  2005.05  [Refereed]

     View Summary

    We have performed narrow-band imaging observations with the Very Large Telescope, aimed at detecting the Lyman continuum (LC) flux escaping from galaxies at z similar to 3. We do not find any significant LC flux from our sample of two galaxies in the Hubble Deep Field South, at z = 3.170 and 3.275. The corresponding lower limits on the F-1400/F-900 flux density ( per Hz) ratio are 15.6 and 10.2 ( 3-sigma confidence level). After correction for the intergalactic hydrogen absorption, the resulting limits on the relative escape fraction of the LC are compared with those obtained by different approaches, at similar or lower redshifts. One of our two objects has a relative escape fraction lower than the detection reported by Steidel et al. in a composite spectrum of z similar to 3 galaxies. A larger number of objects is required to reach a significant conclusion. Our comparison shows the potential of narrow-band imaging for obtaining the best limit on the relative escape fraction at z similar to 3. Stacking a significant number of galaxies observed through a narrow-band filter would provide constraint on the galactic contribution to the cosmic reionization.

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    62
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    (Scopus)
  • Attenuation law of normal disc galaxies with clumpy distributions of stars and dust

    AK Inoue

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   359 ( 1 ) 171 - 182  2005.05  [Refereed]

     View Summary

    We investigate the attenuation law seen through an interstellar medium (ISM) with clumpy spatial distributions of stars and dust. The clumpiness of the dust distribution is introduced by a multiphase ISM model. We solve a set of radiative transfer equations with multiple anisotropic scatterings through the clumpy ISM in a one-dimensional plane-parallel geometry by using the mega-grain approximation, in which dusty clumps are regarded as very large particles (i.e. mega-grains). The clumpiness of the stellar distribution is introduced by the youngest stars embedded in the clumps. We assume a smooth spatial distribution for older stars. The youngest stars are surrounded by denser dusty gas and suffer stronger attenuation than diffuse older stars (i.e. age-selective attenuation). The apparent attenuation law is a composite of the attenuation laws for the clumpy younger stars and for the diffuse older stars with a luminosity weight. In general, the stellar population dominating the luminosity changes from older stars to younger stars as the wavelength decreases. This makes the attenuation law steep; the composite attenuation rapidly increases from small attenuation for older stars at a long wavelength to large attenuation for younger stars at a short wavelength. The resultant attenuation law of normal disc galaxies is expected to be much steeper than that of starburst galaxies observed by Calzetti et al. Finally, the Calzetti attenuation law is regarded as a special case with a large density in our framework.

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    48
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  • Attenuation law of disk galaxies by the mega-grain approximation

    Akio K. Inoue

    European Space Agency, (Special Publication) ESA SP   ( 577 ) 285 - 286  2005

     View Summary

    The attenuation law through the clumpy interstellar medium (ISM) in disk galaxies is investigated. I adopted the mega-grain approximation, in which dusty clumps are regarded as very large particles (i.e. mega-grains), to treat the ISM dumpiness in a 1-D plane-parallel radiative transfer with multiple anisotropic scatterings. Further, a physical model of the dumpiness was introduced as an extention of the multi-phase ISM model. In this framework, the attenuation law is determined by three physical quantities in the ISM: the mean gas density, the mean pressure, and the dust-to-gas ratio. I found that the attenuation law of normal disk galaxies is much steeper than that of starburst galaxies observed by Calzetti et al.

  • Gamma-ray burst formation rate inferred from the spectral peak energy-peak luminosity relation

    D Yonetoku, T Murakami, T Nakamura, R Yamazaki, AK Inoue, K Ioka

    ASTROPHYSICAL JOURNAL   609 ( 2 ) 935 - 951  2004.07  [Refereed]

     View Summary

    We estimate a gamma-ray burst (GRB) formation rate based on the new relation between the spectral peak energy (E-p) and the peak luminosity. The new relation is derived by combining the data of E-p and the peak luminosities by BeppoSAX and BATSE, and it looks considerably tighter and more reliable than the relations suggested by the previous works. Using the new E-p-luminosity relation, we estimate redshifts of the 689 GRBs without known distances in the BATSE catalog and derive a GRB formation rate as a function of the redshift. For the redshift range of 0 less than or equal to z less than or equal to 2, the GRB formation rate increases and is well correlated with the star formation rate, while it keeps constant toward z similar to 12. We also discuss the luminosity function and the redshift dependence of the intrinsic luminosity ( luminosity evolution).

  • Amount of intergalactic dust: constraints from distant supernovae and the thermal history of the intergalactic medium

    AK Inoue, H Kamaya

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   350 ( 2 ) 729 - 744  2004.05  [Refereed]

     View Summary

    In this paper we examine the allowed amount of intergalactic (IG) dust, which is constrained by extinction and reddening of distant Type Ia supernovae (SNe Ia) and the thermal history of the intergalactic medium (IGM) affected by dust photoelectric heating. Based on the observational cosmic star formation history, we find an upper bound of chi, the mass ratio of the IG dust to the total metal in the Universe, as &gt;chiless than or similar to0.1 for 10 Angstromless than or similar toaless than or similar to0.1 mum and chiless than or similar to0.1(a/0.1 mum) for 0.1less than or similar toaless than or similar to1 mum, where a is a characteristic grain size of the IG dust. This upper bound of chisimilar to 0.1 suggests that the dust-to-metal ratio in the IGM is smaller than the current Galactic value. The corresponding allowed density of the IG dust increases from similar to10(-34) g cm(-3) at z=0 to similar to10(-33) g cm(-3) at zsimilar to1, and keeps almost the value toward higher redshift. This causes IG extinction of less than or similar to0.2 mag at the observer's B band for zsimilar to1 sources and that of less than or similar to1 mag for higher redshift sources. Furthermore, if (B-V)similar to0.1 mag at the observer's frame against zgreater than or similar to1 sources is detected, we can conclude that a typical size of the IG dust is less than or similar to100 Angstrom. The signature of the 2175-Angstrom feature of small graphite may be found as a local minimum at zsimilar to2.5 in a plot of the observed E(B-V) as a function of the source redshift. Finally, the IGM mean temperature at zless than or similar to1 can be still higher than 10(4) K, provided the size of the IG dust is less than or similar to100 Angstrom.

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  • Near-infrared colors of gamma-ray burst afterglows and cosmic reionization history

    AK Inoue, R Yamazaki, T Nakamura

    ASTROPHYSICAL JOURNAL   601 ( 2 ) 644 - 653  2004.02  [Refereed]

     View Summary

    We discuss a way to study the cosmic reionization history using near-infrared (NIR) observations of the afterglows of high-redshift (5less than or similar tozless than or similar to25) gamma-ray bursts (GRBs) that will be detected by the Swift satellite. In principle, details of the cosmic reionization history should be imprinted in the NIR spectra of GRB afterglows. However, spectroscopy with a space telescope is required to obtain such information for very high redshifts (zgreater than or similar to15) unless the neutral fraction of the high-z universe is less than 10(-6). The broadband photometry has higher sensitivity than the spectroscopy, so that NIR photometric follow-up of GRB afterglows is very promising for examining cosmic reionization history. A few minutes exposure with a 8 m class ground-based telescope of the afterglows of the high-z GRBs will reveal how many times reionization occurred in the universe.

  • Near-infrared colors of gamma-ray burst afterglows and cosmic reionization history

    AK Inoue, R Yamazaki, T Nakamura

    GAMMA-RAY BURSTS: 30 YEARS OF DISCOVERY   727   514 - 517  2004  [Refereed]

     View Summary

    We propose a method for examining the cosmic reionization history by using near-infrared (NIR) colors of afterglows of high redshift (5 &lt; z &lt; 25) gamma-ray bursts (GRBs) that will be detected by the Swift satellite. The broad-band photometry has a much higher sensitivity than that of the spectroscopy. A prompt NIR photometric follow-up of the high-z GRB afterglows will reveal how many times the reionization occurred in the universe.

  • Evolution of dust-to-metal ratio in galaxies

    AK Inoue

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   55 ( 5 ) 901 - 909  2003.10  [Refereed]

     View Summary

    This paper investigates the evolution of the dust-to-metal ratio in galaxies based on a simple evolution model for the amount of metal and dust with infall. We take into account grain formation in stellar mass-loss gas, grain urowth bv the accretion of metallic atoms in a cold dense cloud, and grain destruction by SN shocks. Especially, we propose that the accretion efficiency is independent of the star-formation history. This predicts various evolutionary tracks in the metallicity (Z)-dust-to-gas ratio (D) plane depending on the star-formation history. In this framework, the observed linear Z-D relation of nearby spiral galaxies can be interpreted as a sequence of a constant galactic age. We emphasize that an observational study of the Z-D relation of galaxies at z similar to 1 is very useful to constrain the efficiencies of dust growth and destruction. We also suggest that the Lyman break galaxies at z similar to 3 have a very low dust-to-metal ratio, typically less than or similar to 0.1. Although the effect of infall on the evolutionary tracks in the Z-D plane is quite small. the dispersion of the infall rate can disturb the Z-D relation with a constant galactic age.

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    93
    Citation
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  • Star formation rate in galaxies from UV, IR, and H alpha estimators

    H Hirashita, Buat, V, AK Inoue

    ASTRONOMY & ASTROPHYSICS   410 ( 1 ) 83 - +  2003.10  [Refereed]

     View Summary

    Infrared (IR) luminosity of galaxies originating from dust thermal emission can be used as an indicator of the star formation rate (SFR). Inoue et al. (2000, IHK) have derived a formula for the conversion from dust IR luminosity to SFR by using the following three quantities: the fraction of Lyman continuum luminosity absorbed by gas (f), the fraction of UV luminosity absorbed by dust (epsilon), and the fraction of dust heating from old (greater than or similar to10(8) yr) stellar populations (eta). We develop a method to estimate those three quantities based on the idea that the various way of SFR estimates from ultraviolet (UV) luminosity (2000 Angstrom luminosity), Halpha luminosity, and dust IR luminosity should return the same SFR. After applying our method to samples of galaxies, the following results are obtained in our framework. First, our method is applied to a sample of star-forming galaxies, finding that f similar to 0.6, epsilon similar to 0.5, and eta similar to 0.4 as representative values. Next, we apply the method to a starburst sample, which shows larger extinction than the star-forming galaxy sample. With the aid of f, epsilon, and eta, we are able to estimate reliable SFRs from UV and/or IR luminosities. Moreover, the Halpha luminosity, if the Halpha extinction is corrected by using the Balmer decrement, is suitable for a statistical analysis of SFR, because the same correction factor for the Lyman continuum extinction (i.e. 1/f) is applicable to both normal and starburst galaxies over all the range of SFR. The metallicity dependence of f and epsilon is also tested: Only the latter proves to have a correlation with metallicity. As an extension of our result, the local (z = 0) comoving density of SFR can be estimated with our dust extinction corrections. We show that all UV, Halpha, and IR comoving luminosity densities at z = 0 give a consistent SFR per comoving volume (similar to3 x 10(-2)h M. yr(-1) Mpc(-3)). Useful formulae for SFR estimate are listed.

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    128
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  • Constraint on intergalactic dust from thermal history of intergalactic medium

    AK Inoue, H Kamaya

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   341 ( 3 ) L7 - L11  2003.05  [Refereed]

     View Summary

    This letter investigates the amount of dust in the intergalactic medium (IGM). The dust photoelectric heating can be the most efficient heating mechanism in the IGM where the density is very small and there are a lot of hard ultraviolet photons. Comparing the observational thermal history of IGM with a theoretical one taking into account the dust photoelectric heating, we can put an upper limit on the dust-to-gas ratio, D, in the IGM. As the rate of the dust photoelectric heating depends on the size of dust, we find the following results: if the grain size is greater than or similar to100 Angstrom, D at z similar to 3 is less than or similar to1/100 Galactic value corresponding to Omega(dust)(IGM)less than or similar to10(-5). On the other hand, if the grain size is as small as similar to10 Angstrom, D is less than or similar to1/1000 Galactic value corresponding to Omega(dust)(IGM)less than or similar to10(-6).

  • Star formation rate from dust infrared emission

    AK Inoue

    ASTROPHYSICAL JOURNAL   570 ( 2 ) L97 - L100  2002.05  [Refereed]

     View Summary

    We examine types of galaxies the conversion formula from dust infrared (IR) luminosity into the star formation rate (SFR) derived by R. C. Kennicutt is applicable to. The ratio of the observed IR luminosity L-IR, to the intrinsic bolometric luminosity of the newly (less than or similar to10 Myr) formed stars, L-SF, of a galaxy can be determined LSF by a mean dust opacity in the interstellar medium and the activity of the current star formation. We find that the area given by these parameters, 0.5 less than or equal to L-IR/L-SF less than or equal to 2.0, is very large, and many nearby normal and active star-forming galaxies really fall in this area. It results from offsetting two effects of a small dust opacity and a large cirrus contribution of normal galaxies relative to starburst galaxies on the conversion of the stellar emission into the dust IR emission. In conclusion, the SFR determined from the IR luminosity under the assumption of L-IR = L-SF, like Kennicutt's, is reliable within a factor of 2 for all galaxies except for dust-rich but quiescent galaxies and extremely dust-poor galaxies.

  • Spatial distribution of dust grains within HII regions

    AK Inoue

    ASTROPHYSICAL JOURNAL   570 ( 2 ) 688 - 696  2002.05  [Refereed]

     View Summary

    We discuss the dust distribution within photoionized regions. Assuming a geometry with a central dust cavity, which is strongly suggested by the literature, we can estimate the cavity radius from the ratio of the infrared and radio fluxes by using a simple transfer model of Lyman continuum photons. We apply the method to a sample of the Galactic H II regions. The estimated typical radius of the dust cavity of the Galactic compact H II regions is about 30% of the Stromgren radius. Taking into account uncertainties in both the observational data and the model, we can reject a dust distribution lacking a central cavity. Therefore, the dust cavity model is supported independently of the previous works. We discuss the formation mechanism of such a dust cavity and its detectability by present and future infrared facilities.

  • Lyman continuum extinction by dust in HII regions of galaxies

    AK Inoue

    ASTRONOMICAL JOURNAL   122 ( 4 ) 1788 - 1795  2001.10  [Refereed]

     View Summary

    We examine Lyman continuum extinction (LCE) in H II regions by comparing infrared fluxes of 49 H II regions in the Galaxy, M31, M33, and the Large Megellanic Cloud with estimated production rates of Lyman continuum photons. A typical fraction of Lyman continuum photons that contribute to hydrogen ionization in the H II regions of three spiral galaxies is less than or similar to 50%. The fraction may become smaller as the metallicity (or dust-to-gas ratio) increases. We examine the LCE effect on estimated star formation rates of galaxies. The correction factor for the Galactic dust-to-gas ratio is 2-5.

  • Effect of dust extinction on estimating the star formation rate of galaxies: Lyman continuum extinction

    AK Inoue, H Hirashita, H Kamaya

    ASTROPHYSICAL JOURNAL   555 ( 2 ) 613 - 624  2001.07  [Refereed]

     View Summary

    We reexamine the effect of Lyman continuum (lambda less than or equal to 912 Angstrom )extinction (LCE) by dust in H II regions in detail and discuss how it affects the estimation of the global star formation rate (SFR) of galaxies. To clarify the first issue, we establish two independent methods for estimating a parameter of LCE (f), which is defined as the fraction of Lyman continuum photons contributing to hydrogen ionization in an H II region. One of those methods determines f from the set of Lyman continuum flux, electron density, and metallicity. In the framework of this method, as the metallicity and/or the Lyman photon flux increase, f is found to decrease. The other method determines f from the ratio of infrared flux to Lyman continuum flux. Importantly, we show that f less than or similar to 0.5 via both methods in many H II regions of the Galaxy. Thus, it establishes that dust in such H II regions absorbs significant amount of Lyman continuum photons directly. To examine the second issue, we approximate f to a function of only the dust-to-gas mass ratio (i.e., metallicity), assuming a parameter fit for the Galactic H II regions. We find that a characteristic (f) over cap, which is defined as f averaged over a galaxywide scale, is 0.3 for the nearby spiral galaxies. This relatively small (f) over cap indicates that a typical increment factor due to LCE for estimating the global SFR (1/(f) over cap) is large (similar to3) for the nearby spiral galaxies. Therefore, we conclude that the effect of LCE is not negligible relative to other uncertainties of estimating the SFR of galaxies.

  • Emission from dust in galaxies: Metallicity dependence

    H Hirashita, AK Inoue, H Kamaya, H Shibai

    ASTRONOMY & ASTROPHYSICS   366 ( 1 ) 83 - 90  2001.01  [Refereed]

     View Summary

    Infrared (IR) dust emission from galaxies is frequently used as an indicator of star formation rate (SFR). However, the effect of the dust-to-gas ratio (i.e., amount of the dust) on the conversion law from IR luminosity to SFR has not so far been considered. Then, in this paper, we present a convenient analytical formula including this effect. In order to obtain the dependence on the dust-to-gas ratio, we extend the formula derived in our previous paper, in which a theoretical formula converting IR luminosity to SFR was derived. That formula was expressed as SFR/(M. yr(-1)) = {3.3 10-(10) (1-eta)/(0.4 - 0.2 + 0.6 epsilon)}(L-IR/L.), where f is the fraction of ionizing photons absorbed by hydrogen, epsilon is the efficiency of dust absorption for nonionizing photons, eta is the cirrus fraction of observed dust luminosity, and L-IR is the observed luminosity of dust emission in the 8-1000-mum range. Our formula explains the IR excess of the Galaxy and the Large Magellanic Cloud. In the current paper, especially, we present the metallicity dependence of our conversion law between SFR and LIR This is possible since both f and epsilon can be estimated via the dust-to-gas ratio, which is related to metallicity. We have confirmed that the relation between the metallicity and the dust-to-gas ratio is applied to both giant and dwarf galaxies. Finally, we apply the result to the cosmic star formation history. We find that the comoving SFR at z similar to 3 calculated from previous empirical formulae is underestimated by a factor of 4-5.

  • Structural model of molecular cloud complexes: Mass, size, and external pressure

    AK Inoue, H Kamaya

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   52 ( 6 ) L47 - L51  2000.12  [Refereed]

     View Summary

    We investigate the structure of the molecular cloud complexes (MCCs) as a group of several giant molecular clouds (GMCs) in the Galaxy. We then find that the mass-size relation which has been reported for the GMCs is well-established even for very large MCCs, whose sizes are about 1 kpc. Since the horizontal size of the MCCs is larger than the thickness of the galactic disk, we can no longer consider the MCCs to be spherical. Thus, we construct a structural model of the MCCs, adopting a rectangular-solid geometry. As a result, our model explains the observed mass-size relation of the MCCs very well. From the estimated external pressure around the MCCs, we find that they are in a rough pressure balance with the interstellar medium. Moreover, we find there is an observational deficiency of the MCCs with a large size and surface density. We thus suggest that the external pressure has a significant effect on the structure and evolution of the MCCs. We also discuss the effect of H II regions in the MCCs.

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    6
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  • Star formation efficiency in the central 1 kiloparsec region of early-type spiral galaxies

    AK Inoue, H Hirashita, H Kamaya

    ASTRONOMICAL JOURNAL   120 ( 5 ) 2415 - 2422  2000.11  [Refereed]

     View Summary

    It has been reported recently that there are some early-type spiral (Sa-Sab) galaxies with evident star-forming regions that concentrate in their own central 1 kpc. In such central region, is the mechanism of the star formation distinct from that in disks of spiral galaxies? To discover this, we estimate the star formation efficiency (SFE) in this central 1 kpc star-forming region of some early-type spiral galaxies, taking account of the condition required for this 1 kpc region to be self-gravitating. Using two indicators of the present star formation rate (H alpha and infrared luminosity), we estimate the SFE to a few percent. This is equivalent to the observational SFE in the disks of late-type spiral (Sb-) galaxies. This coincidence may support the universality of the mean SFE of spiral galaxies reported in the recent studies, that is, we find no evidence of a distinct mechanism of the star formation in the central 1 kpc region of early-type galaxies. Also, we examine the structure of the central star-forming region and discuss a method for estimating the mass of star-forming regions.

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Books and Other Publications

  • 新天文学事典

    井上昭雄, 釜谷秀幸( Part: Joint author)

    講談社  2013.03

     View Summary

    講談社ブルーバックスシリーズで出版された最新の天文学の解説書。『第13章星間物質』では、星間空間に存在するガス、宇宙塵、磁場、宇宙線、放射場などの状態や物理・化学過程について、基礎から最新の知見まで概説した。

Misc

  • 北半球最高感度ミリ波サブミリ波ヘテロダイン受信システムLMT-FINER I.デジタルサイドバンド分離広帯域分光計ファームウェアの開発

    田村陽一, 萩本将都, 谷口暁星, 山本宏昭, 川邉良平, 鎌崎剛, 小嶋崇文, 酒井剛, 原田健一, 谷口達, 小関研介, 田中邦彦, 廿日出文洋, 竹腰達哉, 河野孝太郎, 吉村勇紀, 井上昭雄, 橋本拓也

    日本天文学会年会講演予稿集   2020  2020

    J-GLOBAL

  • Large Submillimeter Telescope (LST): 5

    河野孝太郎, 廿日出文洋, 竹腰達哉, 江草芙実, 田村陽一, 谷口暁星, 井上昭雄, 川邊良平, 大島泰, 石井峻, 遠藤光, 唐津謙一, 梅畑豪紀, 濤崎智佳

    日本天文学会年会講演予稿集   2020  2020

    J-GLOBAL

  • Discovery of the Most Distant Oxygen with ALMA

      110 ( 4 ) 274 - 281  2017.04

    CiNii

  • Mid-Infrared Imaging of Protoplanetary Disks around Young Intermediate-Mass Star

    Honda Mitsuhiko, Maaskant Koen, Okamoto Yoshiko K., Kataza Hirokazu, Yamashita Takuya, Miyata Takashi, Sako Shigeyuki, Fujiyoshi Takuya, Sakon Itsuki, Fujiwara Hideaki, Kamizuka Takafumi, Mulders Gijs D., Lopez-Rodriguez Enrique, Packham Christpher, Inoue Akio K., Onaka Takashi

    Science journal of Kanagawa University   26   23 - 31  2015

    CiNii

  • Dust formation history of galaxies : A critical role of metallicity for the dust mass growth by accreting materials in the interstellar medium

    ASANO Ryosuke S., TAKEUCHI Tsutomu T., HIRASHITA Hiroyuki, INOUE Akio K.

    EPS : Earth, Planets and Space   65 ( 3 ) 213 - 222  2013.03

    CiNii

  • Observations of Water Ice Grains in the Protoplanetary Disk Around Herbig Be Star HD100546

    Honda Mitsuhiko, Kudo Tomoyuki, Inoue Akio, Nakamoto Taishi, Fukagawa Misato, Tamura Motohide, Terada Hiroshi, Takato Naruhisa

    Science journal of Kanagawa University   24   25 - 30  2013

    CiNii

  • WISH for deep and wide NIR surveys

    Toru Yamada, Ikuru Iwata, Makiko Ando, Mamoru Doi, Tomotsugu Goto, Yuji Ikeda, Masatoshi Imanishi, Akio K. Inoue, Satoru Iwamura, Nobuyuki Kawai, Masakazu A.R. Kobayashi, Tadayuki Kodama, Yutaka Komiyama, Mariko Kubo, Hideo Matsuhara, Ken Mawatari, Yoshiki Matsuoka, Tomoki Morokuma, Hidehiko Nakaya, Kouji Ohta, Atsushi Okamoto, Sinki Oyabu, Yoichi Sato, Hiroyuki Sugita, Ryo Tsutsui, Chihiro Tokoku, Jun Toshikawa, Saku Tsuneta, Takehiko Wada, Kiyoto Yabe, Naoki Yasuda, Daisuke Yonetoku

    Proceedings of SPIE - The International Society for Optical Engineering   8442   84421A  2012

     View Summary

    WISH, Wide-field Imaging Surveyor for High-redshiftt, is a space mission concept to conduct very deep and widefield surveys at near infrared wavelength at 1-5μm to study the properties of galaxies at very high redshift beyond the epoch of cosmic reionization. The concept has been developed and studied since 2008 to be proposed for future JAXA/ISAS mission. WISH has a 1.5m-diameter primary mirror and a wide-field imager covering 850 arcmin2. The pixel scale is 0.155 arcsec for 18μm pitch, which properly samples the diffraction-limited image at 1.5μm. The main program is Ultra Deep Survey (UDS) covering 100 deg2 down to 28AB mag at least in five broad bands. We expect to detect &gt
    104 galaxies at z=8-9, 10 3-104 galaxies at z=11-12, and 50-100 galaxies at z&gt
    14, many of which can be feasible targets for deep spectroscopy with Extremely Large Telescopes. With recurrent deep observations, detection and light curve monitoring for type-Ia SNe in rest-frame infrared wavelength is also conducted, which is another main science goal of the mission. During the in-orbit 5 years observations, we expect to detect and monitor &gt
    2000 type-Ia SNe up to z̃2. WISH also conducts Ultra Wide Survey, covering 1000deg2 down to 24-25AB mag as well as Extreme Survey, covering a limited number of fields of view down to 29-30AB mag. We here report the progress of the WISH project including the basic telescope and satellite design as well as the results of the test for a proto-model of the flip-type filter exchanger which works robustly near 100K. © 2012 SPIE.

    DOI

  • The origin of dust in galaxies revisited : the mechanism determining dust content

    INOUE Akio K.

    EPS : Earth, Planets and Space   63 ( 10 ) 1027 - 1039  2011.10

    CiNii

  • 224 AB Aur原始惑星系円盤のpre-transitional disk的性質(オーラルセッション6 観測)

    本田 充彦, 井上 昭雄, 岡本 美子, 片ざ 宏一, 藤原 英明, 深川 美里, 山下 卓也, 藤吉 拓哉, 田村 元秀, 橋本 淳, 宮田 隆志, 酒向 重行, 左近 樹, 上塚 貴史, 尾中 敬

    日本惑星科学会秋期講演会予稿集   2010   49 - 49  2010.10

    CiNii

  • Current status and future of infrared astronomy

    INOUE Akio K.

      2010 ( 1 ) 13 - 16  2010.01

    CiNii

  • WISH: Wide-field imaging surveyor for high-redshift

    Toru Yamada, Mamoru Doi, Tomotsugu Gotc, Yuji Ikeda, Masatoshi Imanishi, Akio Inoue, Satoru Iwamura, Ikuru Iwata, Nobuyuki Kawai, Masakazu A.R. Kobayashie, Tadayuki Kodama, Yutaka Komiyama, Hideo Matsuhara, Yoshiki Matsuoka, Tomoki Morokuma, Kouji Ohta, Shinki Oyabu, Yoichi Sato, Hiroyuki Sugita, Ryo Tsutsui, Chihiro Tokoku, Saku Tsuneta, Takehiko Wada, Kiyoto Yabe, Naoki Yasuda, Daisuke Yonetoku

    Proceedings of SPIE - The International Society for Optical Engineering   7731   77311Q  2010

     View Summary

    WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe. We will launch a 1.5m telescope equipped with 1000 arcmin2 wide-field NIR camera by late 2010's in order to conduct unique ultra-deep and wide-area sky surveys at 1-5 micron. The primary science goal of WISH mission is pushing the high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated survey strategy. We expect to detect ∼ 104 galaxies at z=8-9, ∼ 3-6×103 galaxies at z=11-12, and ∼50-100 galaxies at z=14-17 within about 5 years of the planned mission life time. It is worth mentioning that a large fraction of these objects may be bright enough for the spectroscopic observations with the extremely large telescopes. By adopting the optimized strategy for the recurrent observations to reach the depth, we also use the surveys to detect transient objects. Type Ia Supernova cosmology is thus another important primary goal of WISH. A unique optical layout has been developed to achieve the diffraction-limited imaging at 1-5micron over the required large area. Cooling the mirror and telescope to ∼100K is needed to achieve the zodiacal light limited imaging and WISH will achieve the required temperature by passive cooling in the stable thermal environment at the orbit near Sun-Earth L2. We are conducting the conceptual studies and development for the important components of WISH including the exchange mechanism for the wide-field filters as well as the primary mirror fixation. © 2010 SPIE.

    DOI

  • Report of 27th Grain Formation Workshop/Dust in Galaxies 2009

    INOUE Akio K.

    Planetary People   18 ( 4 ) 242 - 243  2009.12

    CiNii

  • Looking for Ionizing Photons Escaping from Galaxies

    INOUE Akio K., IWATA Ikuru

    The Astronomical herald   100 ( 4 ) 174 - 183  2007.03

    CiNii

  • Evolution of the Escape Fraction of Ionizing Photons from Galaxies and the Cosmic Reionization

    Inoue, Akio K

    Osaka Sangyo University, Natural Sciences   ( 117 ) 1 - 16  2006.02  [Refereed]

    Article, review, commentary, editorial, etc. (bulletin of university, research institution)  

     View Summary

    ビッグバンの38万年後にいったん中性化した宇宙が、その後数億年程度で再び電離状態になる、宇宙再電離過程についての研究。形成途中の若い銀河からの電離光子供給量が、現在の宇宙に比べて過去の宇宙、つまり再電離期に近い時期ほど多かった可能性を初めて指摘した。

  • Chemical Evolution and Far-Infrared Emission of Galaxies

    Hiroyuki HIRASHITA, Akio K. INOUE, Hideyuki KAMAYA

    The Institute of Space and Astronautical Science report. S.P.   14   115 - 122  2000.12

     View Summary

    Infrared (IR) dust emission from galaxies is frequently used as an indicator of starformation rate (SFR). However, the effect of dust-to-gas ratio, or amount of dust, on the con-version law from IR luminosity to SFR has not been considered. In this paper, we present aconvenient formula including the effect. In order to obtain the dependence of the dust-to-gasratio, we extend the formula derived in our previous paper, in which a theoretical formula con-verting IR luminosity to SFR was derived. That formula was expressed as SFR=(M yr-1) ={3.3 ×10-10(1-η)/(0.4 - 0.2f + 0.6ε)}(LIR=L), where f is the fraction of ionizing photons ab-sorbed by hydrogen, εis the effciency of dust absorption for nonionizing photons, ηis the cirrusfraction of observed dust luminosity, and LIR is the observed luminosity of dust emission in the8-1000-μm range. Throughout the current discussion, we construct an algorithm to relate f andε, both of which depend on the dust-to-gas ratio, to the metallicity, by adopting a galactic relationbetween dust-to-gas ratio and metallicity. Thus, we estimate the metallicity dependence of ourformula. We apply the result to the cosmic star formation history and find that the comoving SFRat z 〜 3 calculated from previous empirical formulae is underestimated by the factor of 4. Finally,we comment on the HII/L2 mission (SPICA).

    CiNii

▼display all

Research Projects

  • すばるHSC狭帯域深宇宙探査で暴く宇宙再電離:CHORUSプロジェクト

    Project Year :

    2017.04
    -
    2021.03
     

  • すばるHSC観測と宇宙再電離大規模シミュレーションによる電離度マップの描画

    Project Year :

    2014.04
    -
    2017.03
     

    井上 昭雄

  • 宇宙再電離完了期z=6.6における電離度空間分布の描画と再電離光源の探究

    Project Year :

    2011.04
    -
    2015.03
     

  • 銀河の実効的ダスト減光曲線進化とその観測的検証

    Project Year :

    2007
    -
    2010
     

  • 銀河の実効的ダスト減光曲線進化の研究

    Project Year :

    2006
    -
    2007
     

Presentations

  • Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS)

    井上昭雄, 他CHORUSメンバー

    日本天文学会2016年春季年会  (首都大学東京) 

    Presentation date: 2016.03

  • 銀河間空間におけるダストサイズ分布

    井上昭雄

    サイズ分布ビッグピクチャー研究会  (千葉工業大学スカイツリーキャンパス) 

    Presentation date: 2016.02

  • 銀河形成・宇宙再電離と高赤方偏移の超巨大ブラックホール

    井上昭雄, 長峯健太郎

    「超巨大ブラックホール研究推進連絡会」第3回ワークショップ  (甲南大学) 

    Presentation date: 2015.10

  • 赤方偏移9を超える重力レンズ銀河候補からのCIII]1909輝線強度予想

    井上昭雄, 清水一紘

    日本天文学会2015年秋季年会  (甲南大学) 

    Presentation date: 2015.09

  • Prediction of emission line fluxes of gravitationally lensed very high-z galaxies

    Inoue, A. K, Shimizu, I, Okamoto, T, Yoshida, N, Matsuo, H, Tamura, Y

    IAU General Assembly, Meeting #29, id.2246421  (Honolulu) 

    Presentation date: 2015.08

  • Subaru/PFSによる周銀河媒質・銀河間媒質探査の展望

    井上昭雄

    PFSサイエンスワークショップ2015  (国立天文台) 

    Presentation date: 2015.07

  • A comparison of Lyman continuum of population synthesis models and their difference in emission lines of galaxies

    Inoue, A. K, Buat, V, La, ir, As, sique, de Marseille), Burgarella, D. (Laboratoire d'Astrophysique de Marseille

    日本天文学会2015年春季年会  (大阪大学) 

    Presentation date: 2015.03

  • 遠方銀河に関するHST, Subaru, ALMAの最近の成果と将来展望

    井上昭雄

    初代星・初代銀河研究会2015  (東北大学) 

    Presentation date: 2015.01

  • On the intergalactic attenuation for high-z galaxies

    Inoue, A. K

    American Astronomical Society, AAS Meeting #225, id.412.01  (Seattle) 

    Presentation date: 2015.01

  • WISH: Wide-field Imaging Surveyor for High-redshift: Complementary mission with WFIRST

    Inoue, A. K, Yamada, T

    Wide-field InfraRed Surveys: Science and Techniques  (Pasadena) 

    Presentation date: 2014.11

  • Emission lines of LBGs with WISH and their detectability with JWST

    Inoue, Akio K

    WISH+First Galaxies International Workshop  (Marseille) 

    Presentation date: 2014.09

  • On the correction for the intergalactic attenuation of the direct Lyman continuum observation

    Inoue, Akio K

    Lyman Continuum Leakage and Cosmic Reionization  (Stockholm) 

    Presentation date: 2014.08

  • 赤方偏移z=6.6 ライマンブレイク銀河選択用HSC XB945の開発

    井上昭雄, 清水一紘, 林野友紀, 川野元聡

    日本天文学会2014年春季年会  (国際基督教大学) 

    Presentation date: 2014.03

  • ALMAによる赤方偏移8超銀河の遠赤外星雲輝線検出の可能性

    井上昭雄, 清水一紘, 松尾宏, 田村陽一, 吉田直紀, 岡本崇

    日本天文学会2013年秋季年会  (東北大学) 

    Presentation date: 2013.09

  • The Origin of Dust in Galaxies Revisited: the Mechanism Determining Dust Content

    Inoue, A. K

    Physical Processes of Galaxy Formation: Consensus and Challenges  (Aix-en-Provence, France) 

    Presentation date: 2013.07

  • 測光カラーにもとづく種族III銀河の発見方法

    井上昭雄, Erik Zackrisso

    日本天文学会2013年春季年会  (埼玉大学) 

    Presentation date: 2013.03

  • ALMAで観測する赤方偏移8超の[OIII]88ミクロン輝線

    井上昭雄, 松尾宏

    ALMA 時代の宇宙の構造形成理論:第1世代から第n世代へ  (北海道大学) 

    Presentation date: 2013.01

  • HSC "X-band"による銀河間中性度の探査

    井上昭雄, 清水一紘

    すばるHSCサーベイによるサイエンス  (国立天文台) 

    Presentation date: 2012.09

  • 銀河間中性水素吸収の確率分布と遠方銀河の電離光子探査II

    井上昭雄, 岩田生

    日本天文学会2012年秋季年会  (大分大学) 

    Presentation date: 2012.09

  • 銀河ダストの進化

    井上昭雄

    ISM dust mini-WS  (北海道大学) 

    Presentation date: 2012.09

  • WISHによる始原的恒星種族の探査

    井上昭雄

    WISH Science meeting  (国立天文台) 

    Presentation date: 2012.07

  • A possible signature of primordial stellar populations in z=3 Lyman alpha emitters

    Akio K. Inoue

    First Stars IV  (Kyoto) 

    Presentation date: 2012.05

  • 太古のダストとガンマ線バースト

    井上昭雄

    GRBで読み解く太古の宇宙  (東京工業大学) 

    Presentation date: 2012.02

  • 電離光子放射銀河について

    井上昭雄

    初代星形成・初代銀河研究会  (九州大学) 

    Presentation date: 2011.12

  • 銀河吸収線系による高赤方偏移巨大エアバッグ発見 II

    井上昭雄, 林野友紀, 香西克紀

    第4回クェーサー吸収線研究会  (信州大学) 

    Presentation date: 2011.12

  • 銀河のダスト量決定機構:ダスト星間成長のための金属量閾値

    井上昭雄

    日本天文学会2011年秋季年会  (鹿児島大学) 

    Presentation date: 2011.09

  • 銀河の電離光子放射と宇宙再電離

    井上昭雄

    滞在型研究会「全天体形成」  (北海道大学) 

    Presentation date: 2011.08

  • Effects of photosputtering on snowline of the surface of protoplanetary disks

    Inoue Akio K, Oka Akinori (Tokyo, Institute of Technology, Nakamoto Taishi, Tokyo, Institute of Technology, Honda Mitsuhiko, Kanagawa

    Asia-Oceania Geoscience Society, Planetary Sciences, Cosmic Dust  (Taipei, Taiwan) 

    Presentation date: 2011.08

  • 銀河のダスト量決定機構

    井上昭雄

    日本地球惑星科学連合大会  (幕張メッセ) 

    Presentation date: 2011.05

  • Toward observationally resolving snowline in protoplanetary disks

    井上昭雄, 岡明憲, 東京工, 中本泰史, 本田充彦

    第7回太陽系外惑星大研究会  (国立天文台三鷹) 

    Presentation date: 2011.03

  • 極低金属あるいはゼロ金属銀河の静止系可視スペクトルに期待される特徴

    井上昭雄

    日本天文学会2011年春季年会  (筑波大学) 

    Presentation date: 2011.03

  • z=3.1電離光子放射銀河の性質と今後の展開

    井上昭雄

    TMTで切り拓く2020年代の新しい天文学  (国立天文台三鷹キャンパス) 

    Presentation date: 2010.10

  • Snow Line in Protoplanetary Disks

    Inoue, Akio K, Oka, A.(Tokyo, Institute of Technology, Nakamoto, T, Tokyo, Institute of Technology, Honda, M, Kanagawa

    Dust in Planetary Systems  (Jena, Germany) 

    Presentation date: 2010.09

  • z〜6 QSOのダスト量進化モデル:星間雲内ダスト成長の重要性

    井上昭雄

    日本天文学会2010年秋季年会  (金沢大学) 

    Presentation date: 2010.09

  • SSA22領域におけるz=6.5ライマンα輝線銀河探査

    中村江里, 井上昭雄, 林野友紀, 堀江光典, 香西克紀, 藤井智浩, 松田有一, ダーラム

    日本天文学会2010年秋季年会  (金沢大学) 

    Presentation date: 2010.09

  • Balmer Jump Method for Selecting Primordial Galaxies

    Inoue, Akio K

    COSPAR 2010, E12 Probing the High Redshift Universe  (Bremen, Germany) 

    Presentation date: 2010.07

  • Dust growth in the interstellar medium can account for a huge amount of dust in z~6 QSOs

    Inoue, Akio K

    Asia-Oceania Geoscience Society, Planetary Sciences, Cosmic Dust  (Hyderabad, India) 

    Presentation date: 2010.07

  • Dust in z~6 QSOs: Importance of Grain Growth in the Interstellar Medium

    Inoue, Akio K

    MINI-WORKSHOP ON COSMIC DUST  (東京大学数物連携宇宙研究機構) 

    Presentation date: 2010.04

  • A large-scale fluctuation of the neutral hydrogen fraction at the end of the reionizaion epoch revealed by z=6.5 LAEs in the SSA22 field

    Inoue, A. K, Nakamura, E.(Tohoku, Hayashino, T, Tohoku

    Deciphering the Ancient Universe with Gamma-Ray Burst  (京都) 

    Presentation date: 2010.04

  • 赤方偏移3のライマンα輝線銀河が示す種族III星あるいは超低金属星の兆候

    井上昭雄, 岩田生(国立天文台, 香西克紀, 中村江里, 堀江光典, 林野友紀, 松田有一, 山田亨, 秋山正幸, 中村有希

    日本天文学会2010年春季年会  (広島大学) 

    Presentation date: 2010.03

  • 赤外線天文学の現状と将来

    井上昭雄

    光応用・視覚研究会「最近の赤外線テラヘルツ波研究」  (大阪産業大学梅田サテライト教室) 

    Presentation date: 2010.01

  • ライマン「バンプ」銀河:星雲再結合電離光子の脱出と新しい始原星探査法

    井上昭雄

    第22回理論懇シンポジウム  (名古屋大学野依記念学術交流館カンファレンスホール) 

    Presentation date: 2009.12

  • z~6 QSOのダストから探る銀河ダスト量決定機構

    井上昭雄

    第3回クェーサー吸収線系研究会  (雲仙スカイホテル) 

    Presentation date: 2009.12

  • A signature of primordial stars at z=3

    Akio K. Inoue

    Focus week on the epoch of reionization  (東京大学数物連携宇宙研究機構) 

    Presentation date: 2009.12

  • Possible discovery of primordial stars at z=3

    Akio K. Inoue

    Tours symposium 2009  (神戸ファッション美術館オービスホール) 

    Presentation date: 2009.11

  • 赤方偏移6クェーサーのダスト:ISMでのダスト成長の重要性

    井上昭雄

    第27回Grain Formation Workshop / 平成21年度銀河のダスト 研究会  (大阪産業大学梅田サテライト教室) 

    Presentation date: 2009.10

  • 極めて強い電離光子放射を示すライマンα輝線銀河の分光赤方偏移確認

    井上昭雄, 香西克紀, 林野友紀, 中村江里, 岩田生, 松田有一, 秋山正幸, 山田亨,他

    日本天文学会2009年秋季年会  (山口大学) 

    Presentation date: 2009.09

  • Discovery of galaxies emitting strong Lyman continuum at z=3

    INOUE, Akio K

    HARVESTING THE DESERT: THE UNIVERSE BETWEEN REDSHIFT 1 AND 3  (Marseille, France) 

    Presentation date: 2009.07

  • "Discovery of strong Lyman continuum emitting galaxies: Cosmic ""ionizer""?"

    INOUE, Akio K, IWATA, I

    Joint Subaru/Gemini Science Conference  (Kyoto University) 

    Presentation date: 2009.05

  • Subaru narrowband imaging survey of the Lyman continuum from star-forming galaxies at z~3

    Inoue, Akio K, Iwata, Ikuru (NAOJ, Deharveng, J.-M

    REIONIZATION@RINGBERG: The Cosmic Evolution of Helium and Hydrogen  (Ringberg castle, Germany) 

    Presentation date: 2009.03

  • MIR scattered light from protoplanetary disks, and Survey of (ultra)compact HII regions in nearby galaxies

    井上昭雄

    30m望遠鏡での中間赤外線サイエンスの展開  (東京大学本郷キャンパス理学部1号館) 

    Presentation date: 2008.12

  • 銀河間潮汐HIガス塊の物理状態:マゼラニックブリッジとM81群

    井上昭雄

    第2回クェーサー吸収線系研究会  (東京理科大学長万部校) 

    Presentation date: 2008.10

  • 静的原始惑星系円盤における鉛直方向の温度構造に対する散乱の影響

    井上昭雄, 岡明憲, 京, 中本泰史

    日本天文学会2008年秋季年会  (岡山理科大) 

    Presentation date: 2008.09

  • 銀河間ダスト光電効果加熱

    井上昭雄

    初代星・銀河形成研究会  (甲南大学) 

    Presentation date: 2008.09

  • On the detectability of the Lyman continuum from distant galaxies

    Inoue, Akio K, Iwata, Ikuru

    """24th IAP colloquium """"Far away: Light in the young Universe at redshift beyond three"""""""  (Paris, France) 

    Presentation date: 2008.07

  • Intergalactic dust and its photoelectric heating

    Inoue, Akio K, Kamaya Hideyuki

    Cosmic Dust, 5th Annual General Meeting of the Asia Oceania Geosciences Society  (韓国、釜山) 

    Presentation date: 2008.06

  • 銀河間中性水素吸収の確率分布と遠方銀河の電離光子探査

    井上昭雄, 岩田生

    日本天文学会2008年春季年会  (国立オリンピック記念青少年総合センター) 

    Presentation date: 2008.03

  • 散乱光による星周円盤表面のスノーラインの探査

    井上昭雄

    第26回Grain Formation Workshop  (東京大学天文教育研究センター) 

    Presentation date: 2007.12

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