Updated on 2023/01/30

写真a

 
SUGAHARA, Yuma
 
Scopus Paper Info  
Paper Count: 0  Citation Count: 0  h-index: 9

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

Affiliation
Faculty of Science and Engineering, Waseda Research Institute for Science and Engineering
Job title
Junior Researcher(Assistant Professor)

Education

  • 2017.04
    -
    2020.03

    The University of Tokyo   Graduate School of Science   Department of Physics  

  • 2015.04
    -
    2017.03

    The University of Tokyo   Graduate School of Science   Department of Physics  

  • 2011.04
    -
    2015.03

    Kyoto University   Faculty of Science   Faculty of Science  

 

Research Areas

  • Astronomy   Extragalactic astronomy

Papers

  • 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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  • EMPRESS. V. Metallicity Diagnostics of Galaxies over 12 + log(O/H) ≃ 6.9–8.9 Established by a Local Galaxy Census: Preparing for JWST Spectroscopy

    Kimihiko Nakajima, Masami Ouchi, Yi Xu, Michael Rauch, Yuichi Harikane, Moka Nishigaki, Yuki Isobe, Haruka Kusakabe, Tohru Nagao, Yoshiaki Ono, Masato Onodera, Yuma Sugahara, Ji Hoon Kim, Yutaka Komiyama, Chien-Hsiu Lee, Fakhri S. Zahedy

    The Astrophysical Journal Supplement Series   262 ( 1 ) 3 - 3  2022.09

     View Summary

    Abstract

    We present optical-line gas metallicity diagnostics established by the combination of local SDSS galaxies and the largest compilation of extremely metal-poor galaxies (EMPGs) including new EMPGs identified by the Subaru EMPRESS survey. A total of 103 EMPGs are included, covering a large parameter space of magnitude (Mi = −19 to −7) and Hβ equivalent width (10–600 Å), i.e., wide ranges of stellar mass and star formation rate. Using reliable metallicity measurements from the direct method for these galaxies, we derive the relationships between strong optical-line ratios and gas-phase metallicity over the range of $12+\mathrm{log}({\rm{O } }/{\rm{H } })$ ≃ 6.9–8.9, corresponding to 0.02–2 solar metallicity Z. We confirm that the R23 index, ([O iii]+[O ii])/Hβ, is the most accurate metallicity indicator with a metallicity uncertainty of 0.14 dex over the range among various popular metallicity indicators. The other metallicity indicators show large scatters in the metal-poor range (≲0.1 Z). It is explained by our CLOUDY photoionization modeling that, unlike the R23 index, the other metallicity indicators do not use a sum of singly and doubly ionized lines and cannot trace both low- and high-ionization gas. We find that the accuracy of the metallicity indicators is significantly improved if one uses Hβ equivalent width measurements that tightly correlate with ionization states. In this work, we also present the relation of physical properties with the UV-continuum slope β and ionization production rate ξion derived with GALEX data for the EMPGs and provide local anchors of galaxy properties together with the optical-line metallicity indicators that are available in the form of a machine-readable table and useful for forthcoming JWST spectroscopic studies.

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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 > 6

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

    The Astrophysical Journal   935 ( 2 ) 119 - 119  2022.08

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    Abstract

    We present photoionization modeling of galaxy populations at z ∼ 0, 2, and >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 >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 > 6 to 0. Specifically, the z > 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 > 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 > 6. JWST will test the predictions and scenarios for the z > 6 galaxies proposed by our photoionization modeling.

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  • 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

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    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.

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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

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    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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  • 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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  • EMPRESS. III. Morphology, Stellar Population, and Dynamics of Extremely Metal-poor Galaxies (EMPGs): Are EMPGs Local Analogs of High-z Young Galaxies?*

    Yuki Isobe, Masami Ouchi, Takashi Kojima, Takatoshi Shibuya, Kohei Hayashi, Michael Rauch, Shotaro Kikuchihara, Haibin Zhang, Yoshiaki Ono, Seiji Fujimoto, Yuichi Harikane, Ji Hoon Kim, Yutaka Komiyama, Haruka Kusakabe, Chien-Hsiu Lee, Ken Mawatari, Masato Onodera, Yuma Sugahara, Kiyoto Yabe

    The Astrophysical Journal   918 ( 2 ) 54 - 54  2021.09

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  • EMPRESS. II. Highly Fe-enriched Metal-poor Galaxies with ∼1.0 (Fe/O)⊙ and 0.02 (O/H)⊙: Possible Traces of Supermassive (>300 M ⊙) Stars in Early Galaxies* † ‡

    Takashi Kojima, Masami Ouchi, Michael Rauch, Yoshiaki Ono, Kimihiko Nakajima, Yuki Isobe, Seiji Fujimoto, Yuichi Harikane, Takuya Hashimoto, Masao Hayashi, Yutaka Komiyama, Haruka Kusakabe, Ji Hoon Kim, Chien-Hsiu Lee, Shiro Mukae, Tohru Nagao, Masato Onodera, Takatoshi Shibuya, Yuma Sugahara, Masayuki Umemura, Kiyoto Yabe

    The Astrophysical Journal   913 ( 1 ) 22 - 22  2021.05

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  • Extremely Metal-poor Representatives Explored by the Subaru Survey (EMPRESS). I. A Successful Machine-learning Selection of Metal-poor Galaxies and the Discovery of a Galaxy with M* < 106 M ⊙ and 0.016 Z ⊙

    Takashi Kojima, Masami Ouchi, Michael Rauch, Yoshiaki Ono, Kimihiko Nakajima, Yuki Isobe, Seiji Fujimoto, Yuichi Harikane, Takuya Hashimoto, Masao Hayashi, Yutaka Komiyama, Haruka Kusakabe, Ji Hoon Kim, Chien-Hsiu Lee, Shiro Mukae, Tohru Nagao, Masato Onodera, Takatoshi Shibuya, Yuma Sugahara, Masayuki Umemura, Kiyoto Yabe

    The Astrophysical Journal   898 ( 2 ) 142 - 142  2020.08

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  • Three-dimensional Distribution Map of Hi Gas and Galaxies around an Enormous Lyα 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, Yoshiaki Ono, 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, Takatoshi Shibuya, Yuichi Harikane, Seiji Fujimoto, Yi Kuan Chiang, Haibin Zhang, Ryota Kakuma

    Astrophysical Journal   896 ( 1 )  2020.06

     View Summary

    We present an IGM H i tomographic map in a survey volume of 16 × 19 × 131 h-3 commoving Mpc3 (cMpc3) centered at MAMMOTH-1 nebula and three neighboring quasars at z = 2.3. The MAMMOTH-1 nebula is an enormous Lyα nebula (ELAN), hosted by a type-II quasar dubbed MAMMOTH1-QSO, that extends over 1 h-1 cMpc with no clear physical origin. Here we investigate the H i-gas distribution around MAMMOTH1-QSO with the ELAN and three neighboring type-I quasars, making the IGM H i tomographic map with a spatial resolution of 2.6 h -1 cMpc. Our H i tomographic map is reconstructed with H i Lyα forest absorption of bright background objects at z = 2.4-2.9: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate the radial profile of H i overdensity for MAMMOTH1-QSO, and find that MAMMOTH1-QSO resides in a volume with fairly weak H i absorption. This suggests that MAMMOTH1-QSO may have a proximity zone where quasar illuminates and photoionizes the surrounding H i gas and suppresses H i absorption, and that the ELAN is probably a photoionized cloud embedded in the cosmic web. The H i radial profile of MAMMOTH1-QSO is very similar to those of three neighboring type-I quasars at z = 2.3, which is compatible with the AGN unification model. We compare the distributions of the H i absorption and star-forming galaxies in our survey volume, and identify a spatial offset between density peaks of star-forming galaxies and H i gas. This segregation may suggest anisotropic UV background radiation created by star-forming galaxy density fluctuations.

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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, Y., Ouchi, M., Inoue, A.K., Matsuoka, Y., Tamura, Y., Bakx, T., Fujimoto, S., Moriwaki, K., Ono, Y., Nagao, T., Tadaki, K.-I., Kojima, T., Shibuya, T., Egami, E., Ferrara, A., Gallerani, S., Hashimoto, T., Kohno, K., Matsuda, Y., Matsuo, H., Pallottini, A., Sugahara, Y., Vallini, L.

    Astrophysical Journal   896 ( 2 ) 93 - 93  2020  [Refereed]

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  • Balmer Break Galaxy Candidates at z ∼ 6: A Potential View on the Star Formation Activity at z ⪆ 14

    Mawatari, K., Inoue, A.K., Hashimoto, T., Silverman, J., Kajisawa, M., Yamanaka, S., Yamada, T., Davidzon, I., Capak, P., Lin, L., Hsieh, B.-C., Taniguchi, Y., Tanaka, M., Ono, Y., Harikane, Y., Sugahara, Y., Fujimoto, S., Nagao, T.

    Astrophysical Journal   889 ( 2 )  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 x 101 M, 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 2.411 x 104 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 (SI-RD) contributed by progenitors of the BBGs to be 2.4-12 x 10-5 Mc, yr-1 Mpc3 at z > 14 (99.7% confidence range). Our result suggests a smooth evolution of the SFRD beyond z = 8.

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  • Fast outflows identified in early star-forming galaxies at z = 5-6

    Sugahara, Y., Ouchi, M., Harikane, Y., Bouché, N., Mitchell, P.D., Blaizot, J.

    Astrophysical Journal   886 ( 1 )  2019  [Refereed]

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  • A Giant Green Pea Identified in the Spectroscopy of Spatially Extended [O iii] Sources

    Yuma, S., Ouchi, M., Fujimoto, S., Kojima, T., Sugahara, Y.

    Astrophysical Journal   882 ( 1 ) 17 - 17  2019  [Refereed]

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  • 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 )  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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  • First data release of the Hyper Suprime-Cam Subaru Strategic Program

    Hiroaki Aihara, Robert Armstrong, Steven Bickerton, James Bosch, Jean Coupon, Hisanori Furusawa, Yusuke Hayashi, Hiroyuki Ikeda, Yukiko Kamata, Hiroshi Karoji, Satoshi Kawanomoto, Michitaro Koike, Yutaka Komiyama, Dustin Lang, Robert H. Lupton, Sogo Mineo, Hironao Miyatake, Satoshi Miyazaki, Tomoki Morokuma, Yoshiyuki Obuchi, Yukie Oishi, Yuki Okura, Paul A. Price, Tadafumi Takata, Manobu M. Tanaka, Masayuki Tanaka, Yoko Tanaka, Tomohisa Uchida, Fumihiro Uraguchi, Yousuke Utsumi, Shiang-Yu Wang, Yoshihiko Yamada, Hitomi Yamanoi, Naoki Yasuda, Nobuo Arimoto, Masashi Chiba, Francois Finet, Hiroki Fujimori, Seiji Fujimoto, Junko Furusawa, Tomotsugu Goto, Andy Goulding, James E. Gunn, Yuichi Harikane, Takashi Hattori, Masao Hayashi, Krzysztof G. Helminiak, Ryo Higuchi, Chiaki Hikage, Paul T. P. Ho, Bau-Ching Hsieh, Kuiyun Huang, Song Huang, Masatoshi Imanishi, Ikuru Iwata, Anton T. Jaelani, Hung-Yu Jian, Nobunari Kashikawa, Nobuhiko Katayama, Takashi Kojima, Akira Konno, Shintaro Koshida, Haruka Kusakabe, Alexie Leauthaud, Chien-Hsiu Lee, Lihwai Lin, Yen-Ting Lin, Rachel Mandelbaum, Yoshiki Matsuoka, Elinor Medezinski, Shoken Miyama, Rieko Momose, Anupreeta More, Surhud More, Shiro Mukae, Ryoma Murata, Hitoshi Murayama, Tohru Nagao, Fumiaki Nakata, Mana Niida, Hiroko Niikura, Atsushi J. Nishizawa, Masamune Oguri, Nobuhiro Okabe, Yoshiaki Ono, Masato Onodera, Masafusa Onoue, Masami Ouchi, Tae-Soo Pyo, Takatoshi Shibuya, Kazuhiro Shimasaku, Melanie Simet, Joshua Speagle, David N. Spergel, Michael A. Strauss, Yuma Sugahara, Naoshi Sugiyama, Yasushi Suto, Nao Suzuki, Philip J. Tait, Masahiro Takada, Tsuyoshi Terai, Yoshiki Toba, Edwin L. Turner, Hisakazu Uchiyama, Keiichi Umetsu, Yuji Urata, Tomonori Usuda, Sherry Yeh, Suraphong Yuma

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

     View Summary

    The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most important outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope, and it started in 2014 March. This paper presents the first public data release of HSC-SSP. This release includes data taken in the first 1.7yr of observations (61.5 nights), and each of the Wide, Deep, and UltraDeep layers covers about 108, 26, and 4 square degrees down to depths of i ∼ 26.4, ∼26.5, and ∼27.0mag, respectively (5a for point sources). All the layers are observed in five broad bands (grizy), and the Deep and UltraDeep layers are observed in narrow bands as well. We achieve an impressive image quality of 0".6 in the i band in the Wide layer. We show that we achieve 1%-2% point spread function (PSF) photometry (root mean square) both internally and externally (against Pan-STARRS1), and ∼10mas and 40 mas internal and external astrometric accuracy, respectively. Both the calibrated images and catalogs are made available to the community through dedicated user interfaces and database servers. In addition to the pipeline products, we also provide value-added products such as photometric redshifts and a collection of public spectroscopic redshifts. Detailed descriptions of all the data can be found online.

    DOI

    Scopus

    330
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    (Scopus)
  • Evolution of Galactic Outflows at z ∼ 0-2 Revealed with SDSS, DEEP2, and Keck Spectra

    Yuma Sugahara, Masami Ouchi, Lihwai Lin, Crystal L. Martin, Yoshiaki Ono, Yuichi Harikane, Takatoshi Shibuya, Renbin Yan

    Astrophysical Journal   850 ( 1 )  2017.11  [Refereed]

     View Summary

    We conduct a systematic study of galactic outflows in star-forming galaxies at z ∼ 0-2 based on the absorption lines of optical spectra taken from SDSS DR7, DEEP2 DR4, and Keck (Erb et al.). We carefully make stacked spectra of homogeneous galaxy samples with similar stellar mass distributions at z ∼ 0-2 and perform the multicomponent fitting of model absorption lines and stellar continua to the stacked spectra. We obtain the maximum (vmax) and central (vout) outflow velocities and estimate the mass loading factors (η), a ratio of the mass outflow rate to the star formation rate (SFR). Investigating the redshift evolution of the outflow velocities measured with the absorption lines whose depths and ionization energies are similar (Na I D and Mg I at z ∼ 0-1
    Mg II and C II at z ∼ 1-2), we identify, for the first time, that the average value of vmax (vout) significantly increases by 0.05-0.3 dex from z ∼ 0 to 2 at a given SFR. Moreover, we find that the value of η increases from z ∼ 0 to 2 by η ∝ (1 + z)1.2±0.3 at a given halo circular velocity vcir, albeit with a potential systematics caused by model parameter choices. The redshift evolution of vmax (vout) and η is consistent with the galaxy-size evolution and the local velocity-SFR surface density relation and explained by high gas fractions in high-redshift massive galaxies, which is supported by recent radio observations. We obtain a scaling relation of η ∝ νcira for a = -0.2 ± 1.1 in our z ∼ 0 galaxies that agrees with the momentum-driven outflow model (a = -1) within the uncertainties.

    DOI

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    29
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  • Systematic Survey for [O II], [O III], and Hα Blobs at z = 0.1-1.5: The Implication for Evolution of Galactic-scale Outflow

    Suraphong Yuma, Masami Ouchi, Alyssa B. Drake, Seiji Fujimoto, Takashi Kojima, Yuma Sugahara

    Astrophysical Journal   841 ( 2 ) 93 - 93  2017.06  [Refereed]

     View Summary

    We conduct a systematic search for galaxies at z = 0.1 1.5-with [O II]λ3727, [O III]λ5007, or Hal6563 emission lines extended over at least 30 kpc by using deep narrowband and broadband imaging in the-Subaru-XMM Deep Survey field. These extended emission-line galaxies are dubbed [O II], [O III], or Ha blobs. Based on a new selection method that securely selects-extended emission-line galaxies, we find 77 blobs at z = 0.40 1.46-with the isophotal area of emission lines down to 1.2 × 10-18 erg s-1 cm-2 kpc-2. Four of them are spectroscopically confirmed to be [O III] blobs at z=0.83. We identify AGN activities in eight blobs with X-ray and radio data, and find that the fraction of AGN contribution increases with increasing isophotal area of the extended emission. With the Kolmogorov-Smirnov (KS) and Anderson-Darling tests, we confirm that the stellar-mass distributions of Ha and [O II] blobs are not drawn from those of the emitters at the &gt
    90% confidence level in that Ha and [O II] blobs are located at the massive end of the distributions, but cannot reject anull hypothesis of being the same distributions in terms of the specific star formation rates. It is suggested that galactic-scale outflows tend to be more prominent in more massive star-forming galaxies. Exploiting our sample homogeneously selected over the large area, we derive the number densities of blobs at each epoch. The number densities of blobs decrease drastically with redshifts at a rate that is larger than that of the decrease of cosmic star formation densities.

    DOI

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    11
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