Updated on 2025/06/01

写真a

 
ONOUE, Masafusa
 
Affiliation
Affiliated organization, Waseda Institute for Advanced Study
Job title
Assistant Professor(non-tenure-track)

Research Experience

  • 2025.04
    -
    Now

    Waseda University   Waseda Institue for Advanced Study   Assistant Professor

  • 2023.11
    -
    2025.03

    The University of Tokyo   Institute for the Physics and Mathematics of the Universe   Project Researcher   Kavli Astrophysics Fellow

Awards

  • PASJ Excellent Paper Award

    2023.03   Astronomical Society of Japan   Subaru High-z Exploration of Low Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8

    Winner: Yoshiki Matsuoka, Masafusa Onoue, Nobunari Kashikawa, et al.

Media Coverage

  • 初期宇宙のカギ握る「超巨大ブラックホール」、世界初の成果で見えてきた、銀河との“じつに密接”な関係

    Internet

    Author: Other  

    世界トップレベル研究拠点プログラム(WPI)   WPIで生まれた研究  

    2024.03

  • BHと銀河の起源に迫る

    Newspaper, magazine

    Author: Other  

    Kavli IPMU   Kavli IPMU ものしり新聞 15号  

    2023.04

 

Papers

  • Detection of stellar light from quasar host galaxies at redshifts above 6

    Xuheng Ding, Masafusa Onoue, John D. Silverman, Yoshiki Matsuoka, Takuma Izumi, Michael A. Strauss, Knud Jahnke, Camryn L. Phillips, Junyao Li, Marta Volonteri, Zoltan Haiman, Irham Taufik Andika, Kentaro Aoki, Shunsuke Baba, Rebekka Bieri, Sarah E. I. Bosman, Connor Bottrell, Anna-Christina Eilers, Seiji Fujimoto, Melanie Habouzit, Masatoshi Imanishi, Kohei Inayoshi, Kazushi Iwasawa, Nobunari Kashikawa, Toshihiro Kawaguchi, Kotaro Kohno, Chien-Hsiu Lee, Alessandro Lupi, Jianwei Lyu, Tohru Nagao, Roderik Overzier, Jan-Torge Schindler, Malte Schramm, Kazuhiro Shimasaku, Yoshiki Toba, Benny Trakhtenbrot, Maxime Trebitsch, Tommaso Treu, Hideki Umehata, Bram P. Venemans, M. Vestergaard, Fabian Walter, Feige Wang, Jinyi Yang

    Nature   621 ( 7977 ) 51 - 55  2023.06

     View Summary

    The detection of starlight from the host galaxies of quasars during the reionization epoch (z > 6) has been elusive, even with deep Hubble Space Telescope observations 1,2. The current highest redshift quasar host detected 3, at z = 4.5, required the magnifying effect of a foreground lensing galaxy. Low-luminosity quasars 4–6 from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) 7 mitigate the challenge of detecting their underlying, previously undetected host galaxies. Here we report rest-frame optical images and spectroscopy of two HSC-SSP quasars at z > 6 with the JWST. Using near-infrared camera imaging at 3.6 and 1.5 μm and subtracting the light from the unresolved quasars, we find that the host galaxies are massive (stellar masses of 13 × and 3.4 × 1010 M ☉, respectively), compact and disc-like. Near-infrared spectroscopy at medium resolution shows stellar absorption lines in the more massive quasar, confirming the detection of the host. Velocity-broadened gas in the vicinity of these quasars enables measurements of their black hole masses (1.4 × 109 and 2.0 × 108 M ☉, respectively). Their location in the black hole mass–stellar mass plane is consistent with the distribution at low redshift, suggesting that the relation between black holes and their host galaxies was already in place less than a billion years after the Big Bang.

    DOI PubMed

    Scopus

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  • Hidden Little Monsters: Spectroscopic Identification of Low-Mass, Broad-Line AGN at $z&gt;5$ with CEERS

    Kocevski, Dale D., Onoue, Masafusa, Inayoshi, Kohei, Trump, Jonathan R., Arrabal Haro, Pablo, Grazian, Andrea, Dickinson, Mark, Finkelstein, Steven L., Kartaltepe, Jeyhan S., Hirschmann, Michaela, Fujimoto, Seiji, Juneau, Stephanie, Amorin, Ricardo O., Bagley, Micaela B., Barro, Guillermo, Bell, Eric F., Bisigello, Laura, Calabro, Antonello, Cleri, Nikko J., Cooper, M. C., Ding, Xuheng, Grogin, Norman A., Ho, Luis C., Inoue, Akio K., Jiang, Linhua, Jones, Brenda, Koekemoer, Anton M., Li, Wenxiu, Li, Zhengrong, McGrath, Elizabeth J., Molina, Juan, Papovich, Casey, Perez-Gonzalez, Pablo G., Pirzkal, Nor, Wilkins, Stephen M., Yang, Guang, Yung, L. Y. Aaron

    Astrophysical Journal Letters   954 ( 1 )  2023.01

     View Summary

    We report on the discovery of two low-luminosity, broad-line AGN at $z&gt;5$ identified using JWST NIRSpec spectroscopy from the CEERS Survey. We detect broad H$α$ emission from both sources, with FWHM of $2038\pm286$ and $1807\pm207$ km s$^{-1}$, resulting in black hole (BH) masses that are 1-2 dex below that of existing samples of luminous quasars at $z&gt;5$. The first source, CEERS 1670 at $z=5.242$, is 2-3 dex fainter than known quasars at similar redshifts and was previously identified as a candidate low-luminosity AGN based on its rest-frame optical SED. We measure a BH mass of $M_{\rm BH}=1.3\pm0.4\times 10^{7}~M_{\odot}$, confirming that this AGN is powered by the least-massive BH known in the universe at the end of cosmic reionization. The second source, CEERS 3210 at $z=5.624$, is inferred to be a heavily obscured, broad-line AGN caught in a transition phase between a dust-obscured starburst and an unobscured quasar. We estimate its BH mass to be $M_{\rm BH}\simeq 0.9-4.7 \times 10^{7}~M_{\odot}$, depending on the level of dust obscuration assumed. We derive host stellar masses, $M_\star$, allowing us to place constraints on the BH-galaxy mass relationship in the lowest mass range yet probed in the early universe. The $M_{\rm BH}/M_\star$ ratio for CEERS 1670, in particular, is consistent with or higher than the empirical relationship seen in massive galaxies at $z=0$. We examine the emission-line ratios of both sources and find that their location on the BPT and OHNO diagrams is consistent with model predictions for low-metallicity AGN with $Z/Z_\odot \simeq 0.2-0.4$. The spectroscopic identification of low-luminosity, broad-line AGN at $z&gt;5$ with $M_{\rm BH}\simeq 10^{7}~M_{\odot}$ demonstrates the capability of JWST to push BH masses closer to the range predicted for the BH seed population and provides a unique opportunity to study the early stages of BH-galaxy assembly.

    DOI

  • A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

    Masafusa Onoue, Kohei Inayoshi, Xuheng Ding, Wenxiu Li, Zhengrong Li, Juan Molina, Akio Inoue, Linhua Jiang, Luis Ho

    The Astrophysical Journal Letters   942 ( 1 )  2023.01

     View Summary

    <jats:title>Abstract</jats:title>
    <jats:p>We report a candidate of a low-luminosity active galactic nucleus (AGN) at <jats:italic>z</jats:italic> = 5 that was selected from the first near-infrared images of the JWST CEERS project. This source, named CEERS-AGN-z5-1 at absolute 1450 Å magnitude <jats:italic>M</jats:italic>
    <jats:sub>1450</jats:sub> = −19.5 ± 0.3, was found via a visual selection of compact sources from a catalog of Lyman break galaxies at <jats:italic>z</jats:italic> &gt; 4, taking advantage of the superb spatial resolution of the JWST/NIRCam images. The 20 photometric data available from CFHT, Hubble Space Telescope, Spitzer, and JWST suggest that the continuum shape of this source is reminiscent of that for an unobscured AGN, and there is a clear color excess in the filters where the redshifted H<jats:italic>β</jats:italic>+[O <jats:sc>iii</jats:sc>] and H<jats:italic>α</jats:italic> are covered. The estimated line luminosity is <jats:italic>L</jats:italic>
    <jats:sub>H<jats:italic>β</jats:italic>+[O <jats:sc>III</jats:sc>]</jats:sub> = 10<jats:sup>43.0</jats:sup> erg s<jats:sup>−1</jats:sup> and <jats:italic>L</jats:italic>
    <jats:sub>H<jats:italic>α</jats:italic>
    </jats:sub> = 10<jats:sup>42.9</jats:sup> erg s<jats:sup>−1</jats:sup> with the corresponding rest-frame equivalent width EW<jats:sub>H<jats:italic>β</jats:italic>+[O <jats:sc>III</jats:sc>]</jats:sub> = 1100 Å and EW<jats:sub>H<jats:italic>α</jats:italic>
    </jats:sub> = 1600 Å, respectively. Our spectral energy distribution fitting analysis favors the scenario that this object is either a strong broad-line emitter or even a super-Eddington accreting black hole (BH), although a possibility of an extremely young galaxy with moderate dust attenuation is not completely ruled out. The bolometric luminosity, <jats:italic>L</jats:italic>
    <jats:sub>bol</jats:sub> = 2.5 ± 0.3 × 10<jats:sup>44</jats:sup> erg s<jats:sup>−1</jats:sup>, is consistent with those of <jats:italic>z</jats:italic> &lt; 0.35 broad-line AGNs with <jats:italic>M</jats:italic>
    <jats:sub>BH</jats:sub> ∼ 10<jats:sup>6</jats:sup>
    <jats:italic> M</jats:italic>
    <jats:sub>⊙</jats:sub> accreting at the Eddington limit. This new AGN population in the first 1.1 billion years of the universe may close the gap between the observed BH mass range at high redshift and that of BH seeds. Spectroscopic confirmation is awaited to secure the redshift and its AGN nature.</jats:p>

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). VI. Black Hole Mass Measurements of Six Quasars at 6.1 ≤ z ≤ 6.7

    Masafusa Onoue, Nobunari Kashikawa, Yoshiki Matsuoka, Nanako Kato, Takuma Izumi, Tohru Nagao, Michael A. Strauss, Yuichi Harikane, Masatoshi Imanishi, Kei Ito, Kazushi Iwasawa, Toshihiro Kawaguchi, Chien Hsiu Lee, Akatoki Noboriguchi, Hyewon Suh, Masayuki Tanaka, Yoshiki Toba

    Astrophysical Journal   880 ( 2 )  2019.08

     View Summary

    We present deep near-infrared spectroscopy of six quasars at 6.1 ≤ z ≤ 6.7 with Very Large Telescope/X-Shooter and Gemini-N/GNIRS. Our objects, originally discovered through a wide-field optical survey with the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP), have the lowest luminosities (-25.5 mag ≤ M 1450 ≤ -23.1 mag) of the z > 5.8 quasars with measured black hole (BH) masses. From single-epoch mass measurements based on Mg ii λ2798, we find a wide range in BH masses, from M BH = 107.6 to 109.3 M o. The Eddington ratios L bol/L Edd range from 0.16 to 1.1, but the majority of the HSC quasars are powered by M BH ∼ 109 M o supermassive black holes (SMBHs) accreting at sub-Eddington rates. The Eddington ratio distribution of the HSC quasars is inclined to lower accretion rates than those of Willott et al., who measured the BH masses for similarly faint z ∼ 6 quasars. This suggests that the global Eddington ratio distribution is wider than has previously been thought. The presence of M BH ∼ 109 M o SMBHs at z ∼ 6 cannot be explained with constant sub-Eddington accretion from stellar remnant seed BHs. Therefore, we may be witnessing the first buildup of the most massive BHs in the first billion years of the universe, the accretion activity of which is transforming from active growth to a quiescent phase. Measurements of a larger complete sample of z ⪆ 6 low-luminosity quasars, as well as deeper observations with future facilities, will enable us to better understand the early SMBH growth in the reionization epoch.

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  • Minor Contribution of Quasars to Ionizing Photon Budget at z ∼ 6: Update on Quasar Luminosity Function at the Faint End with Subaru/Suprime-Cam

    Masafusa Onoue, Nobunari Kashikawa, Chris J. Willott, Pascale Hibon, Myungshin Im, Hisanori Furusawa, Yuichi Harikane, Masatoshi Imanishi, Shogo Ishikawa, Satoshi Kikuta, Yoshiki Matsuoka, Tohru Nagao, Yuu Niino, Yoshiaki Ono, Masami Ouchi, Masayuki Tanaka, Ji Jia Tang, Jun Toshikawa, Hisakazu Uchiyama

    Astrophysical Journal Letters   847 ( 2 )  2017.10

     View Summary

    We constrain the quasar contribution to the cosmic reionization based on our deep optical survey of z ∼ 6 quasars down to z R = 24.15 using Subaru/Suprime-Cam in three UKIDSS-DXS fields covering 6.5 deg2. In Kashikawa et al. (2015), we select 17 quasar candidates and report our initial discovery of two low-luminosity quasars from seven targets, one of which might be a Ly-emitting galaxy. From an additional optical spectroscopy, none of the four candidates out of the remaining 10 turn out to be genuine quasars. Moreover, the deeper optical photometry provided by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) shows that, unlike the two already-known quasars, the i-z and z-y colors of the last six candidates are consistent with M- or L-type brown dwarfs. Therefore, the quasar luminosity function (QLF) measurement in the previous paper is confirmed. Compiling the QLF measurements from the literature over a wide magnitude range, including an extremely faint AGN candidate from Parsa et al. (2017), to fit them with a double power law, we find that the best-fit faint-end slope is α =-2.04+0.33-0.1 (-1.980.48-0.21 and characteristic magnitude is M∗1450 = -25.8+1.1-1.9(-25.7+1.01.8) in the case of two (one) quasar detection. Our result suggests that, if the QLF is integrated down to M1450 = -18, quasars produce ∼1%-12% of the ionizing photons required to fully ionize the universe at z ∼ 6 with a 2σ confidence level, assuming that the escape fraction is fesc = 1 and the intergalactic medium clumpy factor is C = 3. Even when the systematic uncertainties are taken into account, our result supports the scenario that quasars are the minor contributors of the reionization.

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  • No Galaxy-scale [C ii] Fast Outflow in the z = 6.72 Red Quasar HSC J1205-0000

    Mahoshi Sawamura, Takuma Izumi, Kouichiro Nakanishi, Takeshi Okuda, Michael A. Strauss, Masatoshi Imanishi, Yoshiki Matsuoka, Yoshiki Toba, Hideki Umehata, Takuya Hashimoto, Shunsuke Baba, Tomotsugu Goto, Toshihiro Kawaguchi, Kotaro Kohno, Dragan Salak, Taiki Kawamuro, Kazushi Iwasawa, Masafusa Onoue, Chien Hsiu Lee, Kianhong Lee

    Astrophysical Journal   980 ( 1 )  2025.02

     View Summary

    HSC 120505.09-000027.9 (J1205-0000) is one of the highest redshift (z = 6.72) dust-reddened quasars (red quasars) known to date. We present an improved analysis of Atacama Large Millimeter/submillimeter Array data of the [C ii] 158 μm line and the underlying rest-frame far-infrared (FIR) continuum emission, previously reported in T. Izumi et al. (2021b), toward J1205-0000. Red quasars are thought to be a transitional phase from an obscured starburst to a luminous blue quasar, in some cases associated with massive outflows driven by the active galactic nucleus (AGN). J1205-0000 has a high FIR luminosity, LFIR = 2.5 × 1012 L⊙ and a total IR luminosity of LTIR = 3.5 × 1012 L⊙, corresponding to a star formation rate of ∼528 M⊙ yr−1. With the [C ii]-based dynamical mass of ∼1 × 1011 M⊙, we conclude that J1205-0000 is hosted by a starburst galaxy. In contradiction to T. Izumi et al., our improved analysis shows no hint of a broad component in the [C ii] line spectrum. Thus there is no evidence for a host galaxy-scale fast [C ii] outflow, despite the fact that J1205-0000 has fast nuclear ionized outflows seen in the rest-frame UV. We explore several scenarios for this discrepancy (e.g., the early phase of AGN feedback, reliability of the [C ii] line as a tracer of outflows), and we claim that it is still too early to conclude that there is no significant negative AGN feedback on star formation in this red quasar.

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  • The nature of low-luminosity AGNs discovered by JWST based on clustering analysis: progenitors of low-z quasars?

    Junya Arita, Nobunari Kashikawa, Masafusa Onoue, Takehiro Yoshioka, Yoshihiro Takeda, Hiroki Hoshi, Shunta Shimizu

    Monthly Notices of the Royal Astronomical Society   536 ( 4 ) 3677 - 3688  2025.02

     View Summary

    JWST has discovered many faint AGNs at high-z by detecting their broad Balmer lines. However, their high number density, lack of X-ray emission, and overly high black hole masses with respect to their host stellar masses suggest that they are a distinct population from general type-1 quasars. Here, we present clustering analysis of 27 low-luminosity broad-line AGNs found by JWST (JWST AGNs) at 5 < z < 6 based on cross-correlation analysis with 679 photometrically-selected galaxies to characterize their host dark matter halo (DMH) masses. From the angular and projected cross-correlation functions, we find that their typical DMH mass is log (Mhalo/h-1M⊙) = 11.46-0.25+0.19, and 11.53-0.20+0.15, respectively. This result implies that the host DMHs of these AGNs are ~1 dex smaller than those of luminous quasars. The DMHs of the JWST AGNs at 5 < z < 6 are predicted to grow to 1012-13h-1M⊙ at z ≲ 3, which is comparable to that of a more luminous quasar at the same epoch. Applying the empirical stellar-to-halo mass ratio to the measured DMH mass, we evaluate their host stellar mass as (M*M⊙)=9.48-0.41+0.31 and 9.60-0.33+0.24, which are higher than some of those estimated by the SED fitting. We also evaluate their duty cycle as fduty=0.37-0.15+0.19 per cent, corresponding to ~4/times 106 yr as the lifetime of the JWST AGNs. While we cannot exclude the possibility that the JWST AGNs are simply low-mass type-1 quasars, these results suggest that the JWST AGNs are a different population from type-1 quasars and the progenitors of quasars at z ≲ 3.

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  • Crimson Behemoth: A massive clumpy structure hosting a dusty AGN at z = 4.91

    Takumi S. Tanaka, John D. Silverman, Yurina Nakazato, Masafusa Onoue, Kazuhiro Shimasaku, Yoshinobu Fudamoto, Seiji Fujimoto, Xuheng Ding, Andreas L. Faisst, Francesco Valentino, Shuowen Jin, Christopher C. Hayward, Vasily Kokorev, Daniel Ceverino, Boris S. Kalita, Caitlin M. Casey, Zhaoxuan Liu, Aidan Kaminsky, Qinyue Fei, Irham T. Andika, Erini Lambrides, Hollis B. Akins, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Henry Joy McCracken, Jason Rhodes, Brant E. Robertson, Maximilien Franco, Daizhong Liu, Nima Chartab, Steven Gillman, Ghassem Gozaliasl, Michaela Hirschmann, Marc Huertas-Company, Richard Massey, Namrata Roy, Zahra Sattari, Marko Shuntov, Joseph Sterling, Sune Toft, Benny Trakhtenbrot, Naoki Yoshida, Jorge A. Zavala

    Publications of the Astronomical Society of Japan   76 ( 6 ) 1323 - 1335  2024.12

     View Summary

    The current paradigm for the co-evolution of galaxies and their supermassive black holes postulates that dust-obscured active galactic nuclei (AGNs) represent a transitional phase towards a more luminous and unobscured state. However, our understanding of dusty AGNs and their host galaxies at early cosmic times is inadequate due to observational limitations. Here, we present JWST observations of CID-931, an X-ray-detected AGN at a spectroscopic redshift of zspec = 4.91. Multiband NIRCam imaging from the COSMOS-Web program reveals an unresolved red core, similar to JWST-discovered dusty AGNs. Strikingly, the red core is surrounded by at least eight massive star-forming clumps spread over 1.6 ≈ 10 kpc, each of which has a stellar mass of 109–1010 M and a radius of ∼0.1–1 kpc. The whole system amounts to 1011 M in stellar mass, higher than typical star-forming galaxies at the same epoch. In this system, gas inflows and/or complex merger events may trigger clump formation and AGN activity, thus leading to the rapid formation of a massive galaxy hosting a supermassive black hole. Future followup observations will provide new insights into the evolution of the galaxy–black hole relationship during such transitional phases in the early universe.

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  • No Redshift Evolution in the Fe ii/Mg ii Flux Ratios of Quasars across Cosmic Time

    Danyang Jiang, Masafusa Onoue, Linhua Jiang, Samuel Lai, Eduardo Bañados, George D. Becker, Manuela Bischetti, Sarah E.I. Bosman, Rebecca L. Davies, Valentina D’Odorico, Emanuele Paolo Farina, Martin G. Haehnelt, Chiara Mazzucchelli, Jan Torge Schindler, Fabian Walter, Yongda Zhu

    Astrophysical Journal   975 ( 2 )  2024.11

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    The Fe ii/Mg ii emission line flux ratio in quasar spectra serves as a proxy for the relative Fe to α-element abundances in the broad-line regions of quasars. Due to the expected different enrichment timescales of the two elements, they can be used as a cosmic clock in the early Universe. We present a study of the Fe ii/Mg ii ratios in a sample of luminous quasars exploiting high-quality near-IR spectra taken primarily by the XQR-30 program with VLT XSHOOTER. These quasars have a median bolometric luminosity of log(L bol[erg s−1]) ∼ 47.3 and cover a redshift range of z = 6.0-6.6. The median value of the measured Fe ii/Mg ii ratios is ∼7.9 with a normalized median absolute deviation of ∼2.2. In order to trace the cosmic evolution of Fe ii/Mg ii in an unbiased manner, we select two comparison samples of quasars with similar luminosities and high-quality spectra from the literature, one at intermediate redshifts (z = 3.5-4.8) and the other at low redshifts (z = 1.0-2.0). We perform the same spectral analysis for all these quasars, including the usage of the same iron template, the same spectral fitting method, and the same wavelength fitting windows. We find no significant redshift evolution in the Fe ii/Mg ii ratio over the wide redshift range from z = 1 to 6.6. The result is consistent with previous studies and supports the scenario of a rapid iron enrichment in the vicinity of accreting supermassive black holes at high redshift.

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  • A SPectroscopic Survey of Biased Halos In the Reionization Era (ASPIRE): Broad-line AGN at z = 4−5 Revealed by JWST/NIRCam WFSS

    Xiaojing Lin, Feige Wang, Xiaohui Fan, Zheng Cai, Jaclyn B. Champagne, Fengwu Sun, Marta Volonteri, Jinyi Yang, Joseph F. Hennawi, Eduardo Bañados, Aaron Barth, Anna Christina Eilers, Emanuele Paolo Farina, Weizhe Liu, Xiangyu Jin, Hyunsung D. Jun, Alessandro Lupi, Koki Kakiichi, Chiara Mazzucchelli, Masafusa Onoue, Zhiwei Pan, Elia Pizzati, Sofía Rojas-Ruiz, Jan Torge Schindler, Benny Trakhtenbrot, Yue Shen, Maxime Trebitsch, Ming Yang Zhuang, Ryan Endsley, Romain A. Meyer, Zihao Li, Mingyu Li, Maria Pudoka, Wei Leong Tee, Yunjing Wu, Haowen Zhang

    Astrophysical Journal   974 ( 1 )  2024.10

     View Summary

    Low-luminosity active galactic nuclei (AGNs) with low-mass black holes (BHs) in the early universe are fundamental to understanding the BH growth and their coevolution with the host galaxies. Utilizing JWST NIRCam Wide Field Slitless Spectroscopy, we perform a systematic search for broad-line Hα emitters (BHAEs) at z ≈ 4-5 in 25 fields of the A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE) project, covering a total area of 275 arcmin2. We identify 16 BHAEs with FWHM of the broad components spanning from ∼1000 to 3000 km s−1. Assuming that the broad line widths arise as a result of Doppler broadening around BHs, the implied BH masses range from 107 to 108 M ⊙, with broad Hα-converted bolometric luminosities of 1044.5-1045.5 erg s−1 and Eddington ratios of 0.07-0.47. The spatially extended structure of the F200W stacked image may trace the stellar light from the host galaxies. The Hα luminosity function indicates an increasing AGN fraction toward the higher Hα luminosities. We find possible evidence for clustering of BHAEs: two sources are at the same redshift with a projected separation of 519 kpc; one BHAE appears as a composite system residing in an overdense region with three close companion Hα emitters. Three BHAEs exhibit blueshifted absorption troughs indicative of the presence of high column density gas. We find that the broad-line-selected and photometrically selected BHAE samples exhibit different distributions in the optical continuum slopes, which can be attributed to their different selection methods. The ASPIRE broad-line Hα sample provides a good database for future studies of faint AGN populations at high redshift.

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  • Merging Gas-rich Galaxies That Harbor Low-luminosity Twin Quasars at z = 6.05: A Promising Progenitor of the Most Luminous Quasars

    Takuma Izumi, Yoshiki Matsuoka, Masafusa Onoue, Michael A. Strauss, Hideki Umehata, John D. Silverman, Tohru Nagao, Masatoshi Imanishi, Kotaro Kohno, Yoshiki Toba, Kazushi Iwasawa, Kouichiro Nakanishi, Mahoshi Sawamura, Seiji Fujimoto, Satoshi Kikuta, Toshihiro Kawaguchi, Kentaro Aoki, Tomotsugu Goto

    Astrophysical Journal   972 ( 1 )  2024.09

     View Summary

    We present Atacama Large Millimeter/submillimeter Array [C ii] 158 μm line and underlying far-IR continuum emission observations (0.″57 × 0.″46 resolution) toward a quasar-quasar pair system recently discovered at z = 6.05. The quasar nuclei (C1 and C2) are faint (M 1450 ≳ −23 mag), but we detect very bright [C ii] emission bridging the 12 kpc between the two objects and extending beyond them (total luminosity L [C ii] ≃ 6 × 109 L ⊙). The [C ii]-based total star formation rate of the system is ∼550 M ⊙ yr−1 (the IR-based dust-obscured star formation is ∼100 M ⊙ yr−1), with a [C ii]-based total gas mass of ∼1011 M ⊙. The dynamical masses of the two galaxies are large (∼9 × 1010 M ⊙ for C1 and ∼5 × 1010 M ⊙ for C2). There is a smooth velocity gradient in [C ii], indicating that these quasars are a tidally interacting system. We identified a dynamically distinct, fast-[C ii] component around C1: detailed inspection of the line spectrum there reveals the presence of a broad-wing component, which we interpret as the indication of fast outflows with a velocity of ∼600 km s−1. The expected mass-loading factor of the outflows, after accounting for multiphase gas, is ≳2 − 3, which is intermediate between AGN-driven and starburst-driven outflows. Hydrodynamic simulations in the literature predict that this pair will evolve to a luminous (M 1450 ≲ −26 mag), starbursting (≳1000 M ⊙ yr−1) quasar after coalescence, one of the most extreme populations in the early Universe.

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  • Widespread AGN feedback in a forming brightest cluster galaxy at z = 4.1, unveiled by JWST

    Saxena, A., Overzier, R.A., nd Villar-Mart{\'i}n, M., Heckman, T., Roy, N., Duncan, K.J., R{\"o}ttgering, H., Miley, G., Aydar, C., Best, P., Bosman, S.E.I., Cameron, A.J., Gab{\'a}nyi, K., Humphrey, A., Morais, S., Onoue, M., Pentericci, L., Reynaldi, V., Venemans, B.

    Monthly Notices of the Royal Astronomical Society   531 ( 4 )  2024

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  • Reconstruction of Cosmic Black Hole Growth and Mass Distribution from Quasar Luminosity Functions at z &gt; 4: Implications for Faint and Low-mass Populations in JWST

    Li, W., Inayoshi, K., Onoue, M., He, W., Matsuoka, Y., Pan, Z., Akiyama, M., Izumi, T., Nagao, T.

    Astrophysical Journal   969 ( 1 )  2024

     View Summary

    The evolution of the quasar luminosity function (QLF) is fundamental to understanding the cosmic evolution of black holes (BHs) through their accretion phases. In the era of the James Webb Space Telescope (JWST), Euclid, and Nancy Grace Roman Space Telescope, their unprecedented detection sensitivity and wide survey area can unveil the low-luminosity quasar and low-mass BH population, and provide new insights into quasar host galaxies. We present a theoretical model describing BH growth from initial seeding at $z&gt;20$ to $z\sim 4$,incorporating the duration of accretion episodes, the distribution of Eddington ratios, and the mass dependency of BH accretion rates. By constraining the model parameters with the observed QLFs at $4\leq z\leq6$ across a wide UV luminosity range ($-29&lt;M_{\rm 1450}&lt;-24$), we find that the high-redshift BH population grows rapidly at $z\gtrsim6$, and decelerates the pace in subsequent epochs. Toward lower redshifts ($z&lt;6$), mass-dependent accretion inhibits the growth of high-mass BHs with $M_{\bullet}&gt;10^8~M_\odot$, leading to mass saturation at $M_\bullet\gtrsim 10^{10}~M_\odot$. We predict the BH mass function down to $M_{\bullet}\sim 10^6~M_\odot$ for both unobscured and obscured quasar populations at $4\leq z \leq 11$, offering a benchmark for future observational tests. Our model accounts for the presence of both bright and faint quasars at $z&gt;4$, including those discovered by JWST. Furthermore, our findings suggest two distinct pathways for the early assembly of the BH-galaxy mass correlation: the population with a BH-to-stellar mass ratio near the local value of $M_\bullet/M_{\star}\simeq5\times10^{-3}$ maintains a proximity to the relation through its evolution via moderate growth, while the population that begins to grow above the local relation accretes mass rapidly and becomes as overmassive as $M_\bullet/M_\star \sim 0.01-0.1$ by $z\sim 6$....

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  • Tracing the rise of supermassive black holes A panchromatic search for faint, unobscured quasars at z &amp; 6 with COSMOS-Web and other surveys

    Andika, I.T., Jahnke, K., Onoue, M., Silverman, J.D., Fitriana, I.K., Bongiorno, A., Brinch, M., Casey, C.M., Faisst, A., Gillman, S., Gozaliasl, G., Hayward, C.C., Hirschmann, M., Kocevski, D., Koekemoer, A.M., Kokorev, V., Lambrides, E., Lee, M.M., Rich, R.M., Trakhtenbrot, B., Urry, C.M., Wilkins, S.M., Vijayan, A.P.

    Astronomy and Astrophysics   685  2024

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  • Exploring Low-mass Black Holes through Tidal Disruption Events in the Early Universe: Perspectives in the Era of the JWST, Roman Space Telescope, and LSST Surveys

    Inayoshi, K., Kashiyama, K., Li, W., Harikane, Y., Ichikawa, K., Onoue, M.

    Astrophysical Journal   966 ( 2 )  2024

     View Summary

    The James Webb Space Telescope (JWST) has recently uncovered the presence of low-luminosity active galactic nuclei (AGNs) at z = 4-11. Spectroscopic observations have provided estimates of the nuclear black hole (BH) masses for these sources, extending the low-mass boundary down to M • ∼ 106-7 M ⊙. Despite this breakthrough, the observed lowest mass of BHs is still ≳1-2 orders of magnitude heavier than the predicted mass range of their seed population, thereby leaving the initial mass distribution of massive BHs poorly constrained. In this paper, we focus on UV-to-optical (in the rest frame) flares of stellar tidal disruption events (TDEs) embedded in low-luminosity AGNs as a tool for exploring low-mass BH populations with ≲104-6 M ⊙. We provide an estimate of the TDE rate over z = 4-11, associated with the properties of JWST-detected AGN host galaxies, and we find that deep and wide survey programs with JWST and the Roman Space Telescope (RST) can detect and identify TDEs up to z ≃ 4-7. The predicted detection numbers of TDEs at z > 4 in 1 yr are N TDE ∼ 2 - 10 ( 0.2 - 2 ) for the JADES-Medium (and COSMOS-Web) survey with JWST and N TDE ∼ 2 - 10 ( 8 - 50 ) for the deep (and wide) tiers of the High Latitude Time Domain Survey with RST. We further discuss survey strategies for hunting for transient high-redshift TDEs in wide-field surveys with RST, as well as a joint observation campaign with the Vera C. Rubin Observatory for enhancing the detection number. The high-redshift TDE search will give us a unique opportunity to probe the mass distribution of early BH populations.

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  • Uncovering a Massive z∼7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web

    Lambrides, E., Chiaberge, M., Long, A.S., Liu, D., Akins, H.B., Ptak, A.F., Andika, I.T., Capetti, A., Casey, C.M., Champagne, J.B., Chworowsky, K., Clarke, T.E., Cooper, O.R., Ding, X., Dong, D.Z., Faisst, A.L., Forman, J.Y., Franco, M., Gillman, S., Gozaliasl, G., Hall, K.R., Harish, S., Hayward, C.C., Hirschmann, M., Hutchison, T.A., Jahnke, K., Jin, S., Kartaltepe, J.S., Kleiner, E.T., Koekemoer, A.M., Kokorev, V., Manning, S.M., Martin, C.L., McKinney, J., Norman, C., Nyland, K., Onoue, M., Robertson, B.E., Shuntov, M., Silverman, J.D., Stiavelli, M., Trakhtenbrot, B., Vardoulaki, E., Zavala, J.A., Allen, N., Ilbert, O., McCracken, H.J., Paquereau, L., Rhodes, J., Toft, S.

    Astrophysical Journal Letters   961 ( 1 )  2024

     View Summary

    In this Letter, we report the discovery of the highest redshift, heavily obscured, radio-loud (RL) active galactic nucleus (AGN) candidate selected using JWST NIRCam/MIRI, mid-IR, submillimeter, and radio imaging in the COSMOS-Web field. Using multifrequency radio observations and mid-IR photometry, we identify a powerful, RL, growing supermassive black hole with significant spectral steepening of the radio spectral energy distribution (f1.28 GHz ∼ 2 mJy, q24 μm = −1.1, α1.28−3 GHz = − 1.2, Δα = − 0.4). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/near-infrared (NIR) data and thus infer heavy amounts of obscuration (NH > 1023 cm−2). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo-z of zphot = 7.7-+0.30.4 and estimate an extremely massive host galaxy (log M* = 11.92 0.5M) hosting a powerful, growing supermassive black hole (LBol = 4−12x × 1046 erg s−1). This source represents the farthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs.

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  • Black Hole Mass and Eddington-ratio Distributions of Less-luminous Quasars at z ∼ 4 in the Subaru Hyper Suprime-Cam Wide Field

    He, W., Akiyama, M., Enoki, M., Ichikawa, K., Inayoshi, K., Kashikawa, N., Kawaguchi, T., Matsuoka, Y., Nagao, T., Onoue, M., Oogi, T., Schulze, A., Toba, Y., Ueda, Y.

    Astrophysical Journal   962 ( 2 )  2024

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    We investigate the black hole mass function (BHMF) and Eddington-ratio distribution function (ERDF) of broad-line active galactic nuclei (AGNs) at z = 4, based on a sample of 52 quasars with i < 23.2 at 3.50 ≤ z ≤ 4.25 from the Hyper Suprime-Cam Subaru Strategic Program S16A-Wide2 data set, and 1462 quasars with i < 20.2 in the same redshift range from the Sloan Digital Sky Survey data release 7 quasar catalog. Virial black hole (BH) masses of quasars are estimated using the width of the CIV 1549 Å line and the continuum luminosity at 1350 Å. To obtain the intrinsic broad-line AGN BHMF and ERDF, we correct for the incompleteness in the low-mass and/or low-Eddington-ratio ranges caused by the flux-limited selection. The resulting BHMF is constrained down to log M BH / M ⊙ ∼ 7.5 . In comparison with broad-line AGN BHMFs at z ∼ 2 in the literature, we find that the number density of massive SMBHs peaks at higher redshifts, consistent with the downsizing evolutionary scenario. Additionally, the resulting ERDF shows a negative dependence on BH mass, suggesting more massive SMBHs tend to accrete at lower-Eddington ratios at z = 4. With the derived intrinsic broad-line AGN BHMF, we also evaluate the active fraction of broad-line AGNs among the entire SMBH population at z = 4. The resulting active fraction may suggest a positive dependence on BH mass. Finally, we examine the time evolution of broad-line AGN BHMF between z = 4 and 6 through solving the continuity equation. The results suggest that the broad-line AGN BHMFs at z = 4-6 only show evolution in their normalization, but with no significant changes in their shape.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XVII. Black Hole Mass Distribution at z ∼ 6 Estimated via Spectral Comparison with Low-z Quasars

    Takahashi, A., Matsuoka, Y., Onoue, M., Strauss, M.A., Kashikawa, N., Toba, Y., Iwasawa, K., Imanishi, M., Akiyama, M., Kawaguchi, T., Noboriguchi, A., Lee, C.-H.

    Astrophysical Journal   960 ( 2 )  2024

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    We report the distribution of black hole (BH) masses and Eddingont ratios estimated for a sample of 131 low luminosity quasars in the early cosmic epoch (5.6 < z < 7.0). Our work is based on the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which has constructed a low luminosity quasar sample down to M 1450 ∼ − 21 mag, exploiting the survey data of Hyper Suprime-Cam installed on Subaru Telescope. The discovery spectra of these quasars are limited to the rest-frame wavelengths of ∼1200-1400 Å, which contain no emission lines that can be used as BH mass estimators. In order to overcome this problem, we made use of low-z counterpart spectra from the Sloan Digital Sky Survey, which are spectrally matched to the high-z spectra in overlapping wavelengths. We then combined the C iv emission line widths of the counterparts with the continuum luminosity from the SHELLQs data to estimate BH masses. The resulting BH mass distribution has a range of ∼107-10 M ⊙, with most of the quasars having BH masses ∼108 M ⊙ with sub-Eddington accretion. The present study provides not only a new insight into normal quasars in the reionization epoch, but also a new promising way to estimate BH masses of high-z quasars without near-infrared spectroscopy.

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  • Discovery of Merging Twin Quasars at z = 6.05

    Matsuoka, Y., Izumi, T., Onoue, M., Strauss, M.A., Iwasawa, K., Kashikawa, N., Akiyama, M., Aoki, K., Arita, J., Imanishi, M., Ishimoto, R., Kawaguchi, T., Kohno, K., Lee, C.-H., Nagao, T., Silverman, J.D., Toba, Y.

    Astrophysical Journal Letters   965 ( 1 )  2024

     View Summary

    We report the discovery of two quasars at a redshift of z = 6.05 in the process of merging. They were serendipitously discovered from the deep multiband imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The quasars, HSC J121503.42−014858.7 (C1) and HSC J121503.55−014859.3 (C2), both have luminous (>1043 erg s−1) Lyα emission with a clear broad component (full width at half maximum >1000 km s−1). The rest-frame ultraviolet (UV) absolute magnitudes are M 1450 = − 23.106 ± 0.017 (C1) and −22.662 ± 0.024 (C2). Our crude estimates of the black hole masses provide log ( M BH / M ⊙ ) = 8.1 ± 0.3 in both sources. The two quasars are separated by 12 kpc in projected proper distance, bridged by a structure in the rest-UV light suggesting that they are undergoing a merger. This pair is one of the most distant merging quasars reported to date, providing crucial insight into galaxy and black hole build-up in the hierarchical structure formation scenario. A companion paper will present the gas and dust properties captured by Atacama Large Millimeter/submillimeter Array observations, which provide additional evidence for and detailed measurements of the merger, and also demonstrate that the two sources are not gravitationally lensed images of a single quasar.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XVIII. The Dark Matter Halo Mass of Quasars at z ∼ 6

    Junya Arita, Nobunari Kashikawa, Yoshiki Matsuoka, Wanqiu He, Kei Ito, Yongming Liang, Rikako Ishimoto, Takehiro Yoshioka, Yoshihiro Takeda, Kazushi Iwasawa, Masafusa Onoue, Yoshiki Toba, Masatoshi Imanishi

    The Astrophysical Journal    2023.09

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  • XQR-30: Black hole masses and accretion rates of 42 z ≳ 6 quasars

    Mazzucchelli, C., Bischetti, M., D'Odorico, V., Feruglio, C., Schindler, J. -T., Onoue, M., Bañados, E., Becker, G. D., Bian, F., Carniani, S., Decarli, R., Eilers, A. -C., Farina, E. P., Gallerani, S., Lai, S., Meyer, R. A., Rojas-Ruiz, S., Satyavolu, S., Venemans, B. P., Wang, F., Yang, J., Zhu, Y.

    Astronomy and Astrophysics   676  2023.08

     View Summary

    We present bolometric luminosities, black hole masses, and Eddington ratios for 42 luminous quasars at z ≳ 6 using high signal-to-noise ratio VLT/X-shooter spectra, acquired as part of the enlarged ESO Large Programme XQR-30. In particular, we derived the bolometric luminosities from the rest-frame 3000 Å luminosities using a bolometric correction from the literature, as well as the black hole masses by modeling the spectral regions around the C IV 1549 Å and the Mg II 2798 Å emission lines, with scaling relations calibrated in the Local Universe. We find that the black hole masses derived from both emission lines are in the same range and the scatter of the measurements agrees with expectations from the scaling relations. The Mg II-derived masses are between ∼(0.8−12) ×109 M and the derived Eddington ratios are within ∼0.13−1.73, with a mean (median) of 0.84(0.72). By comparing the total sample of quasars at z &gt; 5.8, from this work and from the literature, to a bolometric luminosity distribution-matched sample at z ∼ 1.5, we find that quasars at high redshift host slightly less massive black holes, which accrete slightly more rapidly than those at lower z, with a difference in the mean Eddington ratios of the two samples of ∼0.27. These findings are in agreement with the results of recent works in the literature....

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  • Uncovering a Massive z~7.65 Galaxy Hosting a Heavily Obscured Radio-Loud QSO Candidate in COSMOS-Web

    Lambrides, Erini, Chiaberge, Marco, Long, Arianna, Liu, Daizhong, Akins, Hollis B., Ptak, Andrew F., Taufik Andika, Irham, Capetti, Alessandro, Casey, Caitlin M., Champagne, Jaclyn B., Chworowsky, Katherine, Cooper, Olivia R., Ding, Xuheng, Faisst, Andreas L., Franco, Maximilien, Gillman, Steven, Gozaliasl, Ghassem, Hall, Kirsten R., Harish, Santosh, Hayward, Christopher C., Hirschmann, Michaela, Hutchison, Taylor A., Jahnke, Knud, Jin, Shuowen, Kartaltepe, Jeyhan S., Koekemoer, Anton M., Kokorev, Vasily, Manning, Sinclaire M., Martin, Crystal L., McKinney, Jed, Norman, Colin, Onoue, Masafusa, Robertson, Brant E., Shuntov, Marko, Silverman, John D., Stiavelli, Massimo, Trakhtenbrot, Benny, Vardoulaki, Eleni, Zavala, Jorge A., Allen, Natalie, Ilbert, Olivier, McCracken, Henry Joy, Paquereau, Louise, Rhodes, Jason, Toft, Sune

       2023.08

     View Summary

    In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud QSO candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED ($f_{1.32 \mathrm{GHz } } \sim 2$ mJy, $q_{24\mu m} = -1.1$, $\alpha_{1.32-3\mathrm{GHz } }=-1.2$, $\Delta \alpha = -0.4$). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of QSO contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (N$_{\mathrm{H } } &gt; 10^{23}$ cm$^{-2}$). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of $z_\mathrm{phot}$ = 7.65$^{+0.4}_{-0.3}$ and estimate an extremely massive host-galaxy ($\log M_{\star} = 11.92 \pm 0.06\,\mathrm{M}_{\odot}$). This source represents the furthest known obscured RL QSO candidate, and its level of obscuration aligns with the most representative but observationally scarce population of QSOs at these epochs....

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  • A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): A First Look at the Rest-frame Optical Spectra of z &gt; 6.5 Quasars Using JWST

    Yang, Jinyi, Wang, Feige, Fan, Xiaohui, Hennawi, Joseph F., Barth, Aaron J., Bañados, Eduardo, Sun, Fengwu, Liu, Weizhe, Cai, Zheng, Jiang, Linhua, Li, Zihao, Onoue, Masafusa, Schindler, Jan-Torge, Shen, Yue, Wu, Yunjing, Bhowmick, Aklant K., Bieri, Rebekka, Blecha, Laura, Bosman, Sarah, Champagne, Jaclyn B., Colina, Luis, Connor, Thomas, Costa, Tiago, Davies, Frederick B., Decarli, Roberto, De Rosa, Gisella, Drake, Alyssa B., Egami, Eiichi, Eilers, Anna-Christina, Evans, Analis E., Farina, Emanuele Paolo, Habouzit, Melanie, Haiman, Zoltan, Jin, Xiangyu, Jun, Hyunsung D., Kakiichi, Koki, Khusanova, Yana, Kulkarni, Girish, Loiacono, Federica, Lupi, Alessandro, Mazzucchelli, Chiara, Pan, Zhiwei, Rojas-Ruiz, Sofía, Strauss, Michael A., Tee, Wei Leong, Trakhtenbrot, Benny, Trebitsch, Maxime, Venemans, Bram, Vestergaard, Marianne, Volonteri, Marta, Walter, Fabian, Xie, Zhang-Liang, Yue, Minghao, Zhang, Haowen, Zhang, Huanian, Zou, Siwei

    The Astrophysical Journal   951 ( 1 )  2023.07

     View Summary

    Studies of rest-frame optical emission in quasars at z &gt; 6 have historically been limited by the wavelengths accessible by ground-based telescopes. The James Webb Space Telescope (JWST) now offers the opportunity to probe this emission deep into the reionization epoch. We report the observations of eight quasars at z &gt; 6.5 using the JWST/NIRCam Wide Field Slitless Spectroscopy as a part of the "A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE)" program. Our JWST spectra cover the quasars' emission between rest frame ~4100 and 5100 Å. The profiles of these quasars' broad Hβ emission lines span a full width at half maximum from 3000 to 6000 km s-1. The Hβ-based virial black hole (BH) masses, ranging from 0.6 to 2.1 billion solar masses, are generally consistent with their Mg II-based BH masses. The new measurements based on the more reliable Hβ tracer thus confirm the existence of a billion solar-mass BHs in the reionization epoch. In the observed [O III] λ λ 4960,5008 doublets of these luminous quasars, broad components are more common than narrow core components (≤ 1200 km s-1), and only one quasar shows stronger narrow components than broad. Two quasars exhibit significantly broad and blueshifted [O III] emission, thought to trace galactic-scale outflows, with median velocities of -610 and -1430 km s-1 relative to the [C II] 158 μm line. All eight quasars show strong optical Fe II emission and follow the eigenvector 1 relations defined by low-redshift quasars. The entire ASPIRE program will eventually cover 25 quasars and provide a statistical sample for the studies of the BHs and quasar spectral properties....

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  • A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST Reveals a Filamentary Structure around a z = 6.61 Quasar

    Wang, F., Yang, J., Hennawi, J.F., Fan, X., Sun, F., Champagne, J.B., Costa, T., Habouzit, M., ndsley, R., Li, Z., Lin, X., Meyer, R.A., Schindler, J., Wu, Y., Ba{\~n}ados, E., Barth, A.J., Bhowmick, A.K., Bieri, R., Blecha, L., Bosman, S., Cai, Z., Colina, L., Connor, T., Davies, F.B., Decarli, R., De Rosa, G., Drake, A.B., Egami, E., Eilers, A.-C., Evans, A.E., Farina, E.P., Haiman, Z., Jiang, L., Jin, X., Jun, H.D., Kakiichi, K., Khusanova, Y., Kulkarni, G., Li, M., Liu, W., Loiacono, F., Lupi, A., Mazzucchelli, C., Onoue, M., Pudoka, M.A., Rojas-Ruiz, S., Shen, Y., Strauss, M.A., Tee, W.L., Trakhtenbrot, B., Trebitsch, M., Venemans, B., Volonteri, M., Walter, F., Xie, Z.-L., Yue, M., Zhang, H., Zhang, H., Zou, S.

    Astrophysical Journal Letters   951 ( 1 )  2023.07

     View Summary

    We present the first results from the JWST program A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE). This program represents an imaging and spectroscopic survey of 25 reionization-era quasars and their environments by utilizing the unprecedented capabilities of NIRCam Wide Field Slitless Spectroscopy (WFSS) mode. ASPIRE will deliver the largest ( $\sim 280\,{\mathrm{arcmin } }^{2}$ ) galaxy redshift survey at 3-4 μm among JWST Cycle 1 programs and provide extensive legacy values for studying the formation of the earliest supermassive black holes, the assembly of galaxies, early metal enrichment, and cosmic reionization. In this first ASPIRE paper, we report the discovery of a filamentary structure traced by the luminous quasar J0305-3150 and 10 [O III] emitters at z = 6.6. This structure has a 3D galaxy overdensity of δ gal = 12.6 over 637 cMpc3, one of the most overdense structures known in the early universe, and could eventually evolve into a massive galaxy cluster. Together with existing VLT/MUSE and ALMA observations of this field, our JWST observations reveal that J0305-3150 traces a complex environment where both UV-bright and dusty galaxies are present and indicate that the early evolution of galaxies around the quasar is not simultaneous. In addition, we discovered 31 [O III] emitters in this field at other redshifts, 5.3 &lt; z &lt; 6.7, with half of them situated at z ~ 5.4 and 6.2. This indicates that star-forming galaxies, such as [O III] emitters, are generally clustered at high redshifts. These discoveries demonstrate the unparalleled redshift survey capabilities of NIRCam WFSS and the potential of the full ASPIRE survey data set....

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  • When Spectral Modeling Meets Convolutional Networks: A Method for Discovering Reionization-era Lensed Quasars in Multiband Imaging Data

    Andika, I.T., Jahnke, K., van der Wel, A., Ba{\~n}ados, E., Bosman, S.E.I., Davies, F.B., Eilers, A.-C., Jaelani, A.T., Mazzucchelli, C., Onoue, M., Schindler, J.-T.

    Astrophysical Journal   943 ( 2 )  2023.02

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    Over the last two decades, around 300 quasars have been discovered at z ≳ 6, yet only one has been identified as being strongly gravitationally lensed. We explore a new approach-enlarging the permitted spectral parameter space, while introducing a new spatial geometry veto criterion-which is implemented via image-based deep learning. We first apply this approach to a systematic search for reionization-era lensed quasars, using data from the Dark Energy Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, and the Wide-field Infrared Survey Explorer. Our search method consists of two main parts: (i) the preselection of the candidates, based on their spectral energy distributions (SEDs), using catalog-level photometry; and (ii) relative probability calculations of the candidates being a lens or some contaminant, utilizing a convolutional neural network (CNN) classification. The training data sets are constructed by painting deflected point-source lights over actual galaxy images, to generate realistic galaxy-quasar lens models, optimized to find systems with small image separations, i.e., Einstein radii of θ E ≤ 1″. Visual inspection is then performed for sources with CNN scores of P lens &gt; 0.1, which leads us to obtain 36 newly selected lens candidates, which are awaiting spectroscopic confirmation. These findings show that automated SED modeling and deep learning pipelines, supported by modest human input, are a promising route for detecting strong lenses from large catalogs, which can overcome the veto limitations of primarily dropout-based SED selection approaches....

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  • XQR-30: The ultimate XSHOOTER quasar sample at the reionization epoch

    D{'}odorico, V., Ba{\~n}ados, E., Becker, G.D., Bischetti, M., Bosman, S.E.I., Cupani, G., Davies, R., Farina, E.P., Ferrara, A., Feruglio, C., Mazzucchelli, C., Ryan-Weber, E., Schindler, J.-T., Sodini, A., Venemans, B.P., Walter, F., Chen, H., Lai, S., Zhu, Y., Bian, F., Campo, S., Carniani, S., Cristiani, S., Davies, F., Decarli, R., Drake, A., Eilers, A.-C., Fan, X., Gaikwad, P., Gallerani, S., Greig, B., Haehnelt, M.G., Hennawi, J., Keating, L., Kulkarni, G., Mesinger, A., Meyer, R.A., Neeleman, M., Onoue, M., Pallottini, A., Qin, Y., Rojas-Ruiz, S., Satyavolu, S., Sebastian, A., Tripodi, R., Wang, F., Wolfson, M., Yang, J., Zanchettin, M.

    Monthly Notices of the Royal Astronomical Society   523 ( 1 )  2023

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  • X-ray emission from a rapidly accreting narrow-line Seyfert 1 galaxy at z = 6.56

    J. Wolf, K. Nandra, M. Salvato, J. Buchner, M. Onoue, T. Liu, R. Arcodia, A. Merloni, S. Ciroi, F. Di Mille, V. Burwitz, M. Brusa, R. Ishimoto, N. Kashikawa, Y. Matsuoka, T. Urrutia, S. G.H. Waddell

    Astronomy and Astrophysics   669  2023.01

     View Summary

    The space density of X-ray-luminous, blindly selected active galactic nuclei (AGN) traces the population of rapidly accreting super-massive black holes through cosmic time. It is encoded in the X-ray luminosity function, whose bright end remains poorly constrained in the first billion years after the Big Bang as X-ray surveys have thus far lacked the required cosmological volume. With the eROSITA Final Equatorial-Depth Survey (eFEDS), the largest contiguous and homogeneous X-ray survey to date, X-ray AGN population studies can now be extended to new regions of the luminosity-redshift space (L2-10 keV > 1045 erg s-1 and z > 6). Aims. The current study aims at identifying luminous quasars at z > 5:7 among X-ray-selected sources in the eFEDS field in order to place a lower limit on black hole accretion well into the epoch of re-ionisation. A secondary goal is the characterisation of the physical properties of these extreme coronal emitters at high redshifts. Methods. Cross-matching eFEDS catalogue sources to optical counterparts from the DESI Legacy Imaging Surveys, we confirm the low significance detection with eROSITA of a previously known, optically faint z = 6:56 quasar from the Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs) survey. We obtained a pointed follow-up observation of the source with the Chandra X-ray telescope in order to confirm the low-significance eROSITA detection. Using new near-infrared spectroscopy, we derived the physical properties of the super-massive black hole. Finally, we used this detection to infer a lower limit on the black hole accretion density rate at z > 6. Results. The Chandra observation confirms the eFEDS source as the most distant blind X-ray detection to date. The derived X-ray luminosity is high with respect to the rest-frame optical emission of the quasar.With a narrow Mgii line, low derived black hole mass, and high Eddington ratio, as well as its steep photon index, the source shows properties that are similar to local narrow-line Seyfert 1 galaxies, which are thought to be powered by young super-massive black holes. In combination with a previous high-redshift quasar detection in the field, we show that quasars with L2-10 keV > 1045 erg s-1 dominate accretion onto super-massive black holes at z _ 6.

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  • The Fraction and Kinematics of Broad Absorption Line Quasars across Cosmic Time

    Bischetti, M., Fiore, F., Feruglio, C., D?Odorico, V., Arav, N., Costa, T., Zubovas, K., Becker, G., Bosman, S.E.I., Cupani, G., Davies, R., Eilers, A.-C., Farina, E.P., Ferrara, A., Gaspari, M., Mazzucchelli, C., Onoue, M., Piconcelli, E., Zanchettin, M.V., Zhu, Y.

    Astrophysical Journal   952 ( 1 )  2023

     View Summary

    Luminous quasars are powerful targets to investigate the role of feedback from supermassive black holes (BHs) in regulating the growth phases of BHs themselves and of their host galaxies, up to the highest redshifts. Here we investigate the cosmic evolution of the occurrence and kinematics of BH-driven outflows, as traced by broad absorption line (BAL) features, due to the C IV ionic transition. We exploit a sample of 1935 quasars at z = 2.1-6.6 with bolometric luminosity log(L bol/erg s-1) ≳ 46.5, drawn from the Sloan Digital Sky Survey and from the X-Shooter legacy survey of Quasars at the Reionization Epoch (XQR-30). We consider rest-frame optical bright quasars to minimize observational biases due to quasar selection criteria. We apply a homogeneous BAL-identification analysis, based on employing composite template spectra to estimate the quasar intrinsic emission. We find a BAL quasar fraction close to 20% at z ~ 2-4, while it increases to almost 50% at z ~ 6. The velocity and width of the BAL features also increase at z ≳ 4.5. We exclude the possibility that the redshift evolution of the BAL properties is due to differences in terms of quasar luminosity and accretion rate. These results suggest significant BH feedback occurring in the 1 Gyr old universe, likely affecting the growth of BHs and, possibly, of their host galaxies, as supported by models of early BH and galaxy evolution....

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  • Resolving Galactic-scale Obscuration of X-Ray AGNs at z ≳ 1 with COSMOS-Web

    Silverman, J.D., Mainieri, V., Ding, X., Liu, D., Jahnke, K., Hirschmann, M., Kartaltepe, J., Lambrides, E., Onoue, M., Trakhtenbrot, B., Vardoulaki, E., Bongiorno, A., Casey, C., Civano, F., Faisst, A., Franco, M., Gillman, S., Gozaliasl, G., Hayward, C.C., Koekemoer, A.M., Kokorev, V., Magdis, G., Marchesi, S., Rich, R.M., Sparre, M., Suh, H., Tanaka, T., Valentino, F.

    Astrophysical Journal Letters   951 ( 2 )  2023

     View Summary

    A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant (z ≳ 1) universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected active galactic nuclei (AGNs) up to z ~ 2. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured (N H &gt; 1023 cm-2) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps E(B - V) of the host galaxies. We compare the mean central value of E(B - V) to the X-ray obscuring column density along the line of sight to the AGN (N H ~ 1023-23.5 cm-2). We find that the extinction due to the host galaxy is present (0.6 ≲ E(B - V) ≲ 0.9; 1.9 ≲ A V ≲ 2.8) and significantly contributes to the X-ray obscuration at a level of N H ~ 1022.5 cm-2 assuming an SMC gas-to-dust ratio that amounts to ≲30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures....

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    6
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  • The Age of Discovery with the James Webb Space Telescope: Excavating the Spectral Signatures of the First Massive Black Holes

    Kohei Inayoshi, Masafusa Onoue, Yuma Sugahara, Akio K. Inoue, Luis C. Ho

    Astrophysical Journal Letters   931 ( 2 )  2022.06

     View Summary

    The James Webb Space Telescope (JWST) will open a new window into the most distant universe and unveil the early growth of supermassive black holes (BHs) in the first galaxies. In preparation for deep JWST imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed BHs. We model the spectral energy distribution of super-Eddington accreting BHs with millions of solar masses in metal-poor galaxies at z ≳ 8, applying postprocess line transfer calculations to radiation hydrodynamical simulation results. Exposures of 10 ks with the NIRCam and MIRI broadband filters are sufficient to detect the radiation flux from the seed BHs with bolometric luminosities of L bol ≃ 1045 erg s-1. While the continuum colors are similar to those of typical low-z quasars, strong Hα line emission with a rest-frame equivalent width EWrest ≃ 1300 Å is so prominent that the line flux affects the broadband colors significantly. The unique colors, for instance, F356W - F560W 3 1 at 7 < z < 8 and F444W - F770W 3 1 at 9 < z < 12, provide robust criteria for photometric selection of rapidly growing seed BHs. Moreover, NIRSpec observations of low-ionization emission lines can test whether the BH is fed via a dense accretion disk at super-Eddington rates.

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  • Co-evolution of massive black holes and their host galaxies at high redshift: Discrepancies from six cosmological simulations and the key role of JWST

    Melanie Habouzit, Masafusa Onoue, Eduardo Banados, Marcel Neeleman, Daniel Angles-Alcazar, Fabian Walter, Annalisa Pillepich, Romeel Dave, Knud Jahnke, Yohan Dubois

    Monthly Notices of the Royal Astronomical Society   511 ( 3 ) 3751 - 3767  2022.04

     View Summary

    The James Webb Space Telescope will have the power to characterize high-redshift quasars at z ≥ 6 with an unprecedented depth and spatial resolution. While the brightest quasars at such redshift (i.e. with bolometric luminosity $L {\rm bol}\geqslant 10 {46}\, \rm erg/s$) provide us with key information on the most extreme objects in the Universe, measuring the black hole (BH) mass and Eddington ratios of fainter quasars with $L_{\rm bol}= 10 {45}-10 {46}\, \rm erg\,s { -1}$ opens a path to understand the build-up of more normal BHs at z ≥ 6. In this paper, we show that the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA large-scale cosmological simulations do not agree on whether BHs at z ≥ 4 are overmassive or undermassive at fixed galaxy stellar mass with respect to the MBH - M scaling relation at z = 0 (BH mass offsets). Our conclusions are unchanged when using the local scaling relation produced by each simulation or empirical relations. We find that the BH mass offsets of the simulated faint quasar population at z ≥ 4, unlike those of bright quasars, represent the BH mass offsets of the entire BH population, for all the simulations. Thus, a population of faint quasars with $L {\rm bol}= 10 {45}-10 {46}\, \rm erg\,s { -1}$ observed by JWST can provide key constraints on the assembly of BHs at high redshift. Moreover, this will help constraining the high-redshift regime of cosmological simulations, including BH seeding, early growth, and co-evolution with the host galaxies. Our results also motivate the need for simulations of larger cosmological volumes down to z ∼6, with the same diversity of subgrid physics, in order to gain statistics on the most extreme objects at high redshift.

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  • Suppression of black-hole growth by strong outflows at redshifts 5.8–6.6

    Bischetti, M., Feruglio, C., D?Odorico, V., Arav, N., Ba{\~n}ados, E., Becker, G., Bosman, S.E.I., Carniani, S., Cristiani, S., Cupani, G., Davies, R., Eilers, A.C., Farina, E.P., Ferrara, A., Maiolino, R., Mazzucchelli, C., Mesinger, A., Meyer, R.A., Onoue, M., Piconcelli, E., Ryan-Weber, E., Schindler, J.-T., Wang, F., Yang, J., Zhu, Y., Fiore, F.

    Nature   605 ( 7909 )  2022

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    55
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  • Subaru High- z Exploration of Low-luminosity Quasars (SHELLQs). XVI. 69 New Quasars at 5.8 &lt; z &lt; 7.0

    Matsuoka, Y., Iwasawa, K., Onoue, M., Izumi, T., Kashikawa, N., Strauss, M.A., Imanishi, M., Nagao, T., Akiyama, M., Silverman, J.D., Asami, N., Bosch, J., Furusawa, H., Goto, T., Gunn, J.E., Harikane, Y., Ikeda, H., Ishimoto, R., Kawaguchi, T., Kato, N., Kikuta, S., Kohno, K., Komiyama, Y., Lee, C.-H., Lupton, R.H., Minezaki, T., Miyazaki, S., Murayama, H., Nishizawa, A.J., Oguri, M., Ono, Y., Ouchi, M., Price, P.A., Sameshima, H., Sugiyama, N., Tait, P.J., Takada, M., Takahashi, A., Takata, T., Tanaka, M., Toba, Y., Utsumi, Y., Wang, S.-Y., Yamashita, T.

    Astrophysical Journal, Supplement Series   259 ( 1 )  2022

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  • Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) – XV. Constraining the cosmic reionization at 5.5 &lt; z &lt; 7

    Lu, T.-Y., Goto, T., Hashimoto, T., Santos, D.J.D., Wong, Y.H.V., Kim, S.J., Hsiao, T.Y.-Y., Kilerci, E., and Ho, S.C.-C., Nagao, T., Matsuoka, Y., Onoue, M., Toba, Y.

    Monthly Notices of the Royal Astronomical Society   517 ( 1 )  2022

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  • Rapid Growth of Seed Black Holes during Early Bulge Formation

    Inayoshi, K., Nakatani, R., Toyouchi, D., Hosokawa, T., Kuiper, R., Onoue, M.

    Astrophysical Journal   927 ( 2 )  2022

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  • Staring at the Shadows of Archaic Galaxies: Damped Ly α and Metal Absorbers Toward a Young z ∼6 Weak-line Quasar

    Andika, I.T., Jahnke, K., Ba{\~n}ados, E., Bosman, S.E.I., Davies, F.B., Eilers, A.-C., Farina, E.P., Onoue, M., Van Der Wel, A.

    Astronomical Journal   163 ( 6 )  2022

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    7
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  • The physical origin for spatially large scatter of IGM opacity at the end of reionization: The IGM Lyα opacity-galaxy density relation

    Ishimoto, R., Kashikawa, N., Kashino, D., Ito, K., Liang, Y., Cai, Z., Yoshioka, T., Okoshi, K., Misawa, T., Onoue, M., Takeda, Y., Uchiyama, H.

    Monthly Notices of the Royal Astronomical Society   515 ( 4 )  2022

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  • The X-shooter/ALMA Sample of Quasars in the Epoch of Reionization. II. Black Hole Masses, Eddington Ratios, and the Formation of the First Quasars

    Farina, E.P., Schindler, J.-T., Walter, F., Ba{\~n}ados, E., Davies, F.B., Decarli, R., Eilers, A.-C., Fan, X., Hennawi, J.F., Mazzucchelli, C., Meyer, R.A., Trakhtenbrot, B., Volonteri, M., Wang, F., Worseck, G., Yang, J., Gutcke, T.A., Venemans, B.P., Bosman, S.E.I., Costa, T., Rosa, G.D., Drake, A.B., Onoue, M.

    Astrophysical Journal   941 ( 2 )  2022

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  • Opening the Era of Quasar-host Studies at High Redshift with JWST

    Ding, X., Silverman, J.D., Onoue, M.

    Astrophysical Journal Letters   939 ( 2 )  2022

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  • Chemical abundance of z∼6 quasar broad-line regions in the XQR-30 sample

    Lai, S., Bian, F., Onken, C.A., Wolf, C., Mazzucchelli, C., Banados, E., Bischetti, M., Bosman, S.E.I., Becker, G., Cupani, G., D{'}Odorico, V., Eilers, A.-C., Fan, X., Farina, E.P., Onoue, M., Schindler, J.-T., Walter, F., Wang, F., Yang, J., Zhu, Y.

    Monthly Notices of the Royal Astronomical Society   513 ( 2 )  2022

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  • On the Connection between Supermassive Black Holes and Galaxy Growth in the Reionization Epoch

    Li, J., Silverman, J.D., Izumi, T., He, W., Akiyama, M., Inayoshi, K., Matsuoka, Y., Onoue, M., Toba, Y.

    Astrophysical Journal Letters   931 ( 1 )  2022

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  • Extreme Nature of Four Blue-excess Dust-obscured Galaxies Revealed by Optical Spectroscopy

    Noboriguchi, A., Nagao, T., Toba, Y., Ichikawa, K., Kajisawa, M., Kato, N., Kawaguchi, T., Matsuhara, H., Matsuoka, Y., Onishi, K., Onoue, M., Tamada, N., Terao, K., Terashima, Y., Ueda, Y., Yamashita, T.

    Astrophysical Journal   941 ( 2 )  2022

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  • Hydrogen reionization ends by z = 5.3: Lyman-α optical depth measured by the XQR-30 sample

    Bosman, S.E.I., Davies, F.B., Becker, G.D., Keating, L.C., Davies, R.L., Zhu, Y., Eilers, A.-C., a, D{'}Odorico, V., Bian, F., Bischetti, M., Cristiani, S.V., Fan, X., Farina, E.P., Haehnelt, M.G., Hennawi, J.F., Kulkarni, G., Mesinger, A., Meyer, R.A., Onoue, M., Pallottini, A., Qin, Y., Ryan-Weber, E., Schindler, J.-T., Walter, F., Wang, F., Yang, J.

    Monthly Notices of the Royal Astronomical Society   514 ( 1 )  2022

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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

    Izumi, T., Onoue, M., Matsuoka, Y., Strauss, M.A., Fujimoto, S., Umehata, H., Imanishi, M., Kawamuro, T., Nagao, T., Toba, Y., Kohno, K., Kashikawa, N., Inayoshi, K., Kawaguchi, T., Iwasawa, K., Inoue, A.K., Goto, T., Baba, S., Schramm, M., Suh, H., Harikane, Y., Ueda, Y., Silverman, J.D., Hashimoto, T., Hashimoto, Y., Ikarashi, S., Iono, D., Lee, C.-H., Lee, K., Minezaki, T., Nakanishi, K., Nakano, S., Tamura, Y., Tang, J.-J.

    Astrophysical Journal   908 ( 2 )  2021

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  • Statistical correlation between the distribution of Lyα emitters and intergalactic medium HI at z ∼ 2.2 mapped by the subaru/hyper suprime-cam

    Liang, Y., Kashikawa, N., Cai, Z., Fan, X., Xavier Prochaska, J., Shimasaku, K., Tanaka, M., Uchiyama, H., Ito, K., Shimakawa, R., Nagamine, K., Shimizu, I., Onoue, M., Toshikawa, J.

    Astrophysical Journal   907 ( 1 )  2021

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  • Optical Spectroscopy of Dual Quasar Candidates from the Subaru HSC-SSP program

    Tang, S., Silverman, J.D., Ding, X., Li, J., Lee, K.-G., Strauss, M.A., Goulding, A., Schramm, M., Kawinwanichakij, L., Xavier Prochaska, J., Hennawi, J.F., Imanishi, M., Iwasawa, K., Toba, Y., Kayo, I., Oguri, M., Matsuoka, Y., Onoue, M., Jahnke, K., Ichikawa, K., Hartwig, T., Kashikawa, N., Kawaguchi, T., Kohno, K., Matsuda, Y., Nagao, T., Ono, Y., Ouchi, M., Shimasaku, K., Suh, H., Suzuki, N., Taniguchi, Y., Ueda, Y., Yasuda, N.

    Astrophysical Journal   922 ( 1 )  2021

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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

    Izumi, T., Matsuoka, Y., Fujimoto, S., Onoue, M., Strauss, M.A., Umehata, H., Imanishi, M., Kohno, K., Kawaguchi, T., Kawamuro, T., Baba, S., Nagao, T., Toba, Y., Inayoshi, K., Silverman, J.D., Inoue, A.K., Ikarashi, S., Iwasawa, K., Kashikawa, N., Hashimoto, T., Nakanishi, K., Ueda, Y., Schramm, M., Lee, C.-H., Suh, H.

    Astrophysical Journal   914 ( 1 )  2021

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  • Random Forests as a Viable Method to Select and Discover High-redshift Quasars

    Wenzl, L., Schindler, J.-T., Fan, X., Andika, I.T., Ba{\~n}ados, E., Decarli, R., Jahnke, K., Mazzucchelli, C., Onoue, M., Venemans, B.P., Walter, F., Yang, J.

    Astronomical Journal   162 ( 2 )  2021

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  • Subaru high-z exploration of low-luminosity quasars (shellqs). xiv. a candidate type ii quasar at z=6.1292

    Onoue, M., Matsuoka, Y., Kashikawa, N., Strauss, M.A., Iwasawa, K., Izumi, T., Nagao, T., Asami, N., Fujimoto, S., Harikane, Y., Hashimoto, T., Imanishi, M., Lee, C.-H., Shibuya, T., Toba, Y.

    Astrophysical Journal   919 ( 1 )  2021

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  • Faint Quasars Live in the Same Number Density Environments as Lyman Break Galaxies at z ∼ 4

    Uchiyama, H., Akiyama, M., Toshikawa, J., Kashikawa, N., Overzier, R., Nagao, T., Ichikawa, K., Marinello, M., Imanishi, M., Tanaka, M., Matsuoka, Y., Komiyama, Y., Ishikawa, S., Onoue, M., Kubo, M., Harikane, Y., Ito, K., Namiki, S., Liang, Y.

    Astrophysical Journal   905 ( 2 )  2021

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  • The X-SHOOTER/ALMA Sample of Quasars in the Epoch of Reionization. I. NIR Spectral Modeling, Iron Enrichment, and Broad Emission Line Properties

    Jan Torge Schindler, Emanuele Paolo Farina, Eduardo Baados, Anna Christina Eilers, Joseph F. Hennawi, Masafusa Onoue, Bram P. Venemans, Fabian Walter, Feige Wang, Frederick B. Davies, Roberto Decarli, Gisella De Rosa, Alyssa Drake, Xiaohui Fan, Chiara Mazzucchelli, Hans Walter Rix, Gábor Worseck, Jinyi Yang

    Astrophysical Journal   905 ( 1 )  2020.12

     View Summary

    We present X-SHOOTER near-IR spectroscopy of a large sample of 38 luminous (M 1450 =-29.0 to-24.4) quasars at 5.78 < z < 7.54, which have complementary [C ii] 158μm observations from ALMA. This X-SHOOTER/ALMA sample provides us with the most comprehensive view of reionization-era quasars to date, allowing us to connect the quasar properties with those of its host galaxy. In this work we introduce the sample, discuss data reduction and spectral fitting, and present an analysis of the broad emission line properties. The measured Fe ii/Mg ii flux ratio suggests that the broad-line regions of all quasars in the sample are already enriched in iron. We also find the Mg ii line to be on average blueshifted with respect to the [C ii] redshift with a median of-391 km s-1. A significant correlation between the Mg ii-[C ii] 158μm and C iv-[C ii] 158μm velocity shifts indicates a common physical origin. Furthermore, we fRequently detect large C iv-Mg ii emission line velocity blueshifts in our sample with a median value of-1848 km s-1. While we find all other broad emission line properties not to be evolving with redshift, the median C iv-Mg ii blueshift is much larger than found in low-redshift, luminosity-matched quasars (-800 km s-1). Dividing our sample into two redshift bins, we confirm an increase of the average C iv-Mg ii blueshift with increasing redshift. Future observations of the rest-frame optical spectrum with the James Webb Space Telescope will be instrumental in further constraining the possible evolution of quasar properties in the epoch of reionization.

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  • The Faint End of the Quasar Luminosity Function at z ∼ 5 from the Subaru Hyper Suprime-Cam Survey

    Mana Niida, Tohru Nagao, Hiroyuki Ikeda, Masayuki Akiyama, Yoshiki Matsuoka, Wanqiu He, Kenta Matsuoka, Yoshiki Toba, Masafusa Onoue, Masakazu A.R. Kobayashi, Yoshiaki Taniguchi, Hisanori Furusawa, Yuichi Harikane, Masatoshi Imanishi, Nobunari Kashikawa, Toshihiro Kawaguchi, Yutaka Komiyama, Hikari Shirakata, Yuichi Terashima, Yoshihiro Ueda

    Astrophysical Journal   904 ( 2 )  2020.12

     View Summary

    We present the quasar luminosity function at z ∼ 5 derived from the optical wide-field survey data obtained as a part of the Subaru strategic program (SSP) with the Hyper Suprime-Cam (HSC). From a ∼81.8 deg2 area in the Wide layer of the HSC-SSP survey, we selected 224 candidates of low-luminosity quasars at z ∼ 5 by adopting the Lyman-break method down to i = 24.1 mag. Based on our candidates and spectroscopically confirmed quasars from the Sloan Digital Sky Survey (SDSS), we derived the quasar luminosity function at z ∼ 5, covering a wide luminosity range of-28.76 < M 1450 <-22.32 mag. We found that the quasar luminosity function is fitted by a double power-law model with a break magnitude of mag. The inferred number density of low-luminosity quasars is lower, and the derived faint-end slope, is flatter than those of previous studies at z ∼ 5. A compilation of the quasar luminosity function at 4 ≤ z ≤ 6 from the HSC-SSP suggests that there is little redshift evolution in the break magnitude and in the faint-end slope within this redshift range, although previous studies suggest that the faint-end slope becomes steeper at higher redshifts. The number density of low-luminosity quasars decreases more rapidly from z ∼ 5 to z ∼ 6 than from z ∼ 4 to z ∼ 5.

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  • Interstellar and Circumgalactic Properties of an Unseen $z=6.84$ Galaxy: Abundances, Ionization, and Heating in the Earliest Known Quasar Absorber

    Simcoe, Robert A., Onoue, Masafusa, Eilers, Anna-Christina, Banados, Eduardo, Cooper, Thomas J., Furesz, Gabor, Hennawi, Joseph F., Venemans, Bram

       2020.11

     View Summary

    We analyze relative abundances and ionization conditions in a strong absorption system at z=6.84, seen in the spectrum of the z=7.54 background quasar ULAS J134208.10+092838.61. Singly ionized C, Si, Fe, Mg, and Al measurements are consistent with a warm neutral medium that is metal-poor but not chemically pristine. Firm non-detections of C IV and Si IV imply that any warm ionized phase of the IGM or CGM has not yet been enriched past the ultra-metal-poor regime (&lt;0.001Z_{solar}), unlike lower redshift DLAs where these lines are nearly ubiquitous. Relative abundances of the heavy elements 794 Myr after the Big Bang resemble those of metal-poor damped Lyman Alpha systems at intermediate redshift and Milky Way halo stars, and show no evidence of enhanced [alpha/Fe], [C/Fe] or other signatures of yields dominated by massive stars. A detection of the CII* fine structure line reveals local sources of excitation from heating, beyond the level of photo-excitation supplied by the CMB. We estimate the total and [CII] cooling rates, balancing against ISM heating sources to develop an heuristic two-phase model of the neutral medium. The implied heating requires a surface density of star formation slightly exceeding that of the Milky Way but not at the level of a strong starburst. For a typical (assumed) NHI=10^{20.6}, an abundance of [Fe/H]=-2.2 matches the columns of species in the neutral phase. To remain undetected in C IV, a warm ionized phase would either need much lower [C/H]&lt;-4.2 over an absorption path of 1 kpc, or else a very small absorption path (a few pc). While still speculative, these results suggest a significant reduction in heavy element enrichment outside of neutral star forming regions of the ISM, as would be expected in early stages of galactic chemical evolution....

    DOI

  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XI. Proximity Zone Analysis for Faint Quasar Spectra at z ∼ 6

    Rikako Ishimoto, Nobunari Kashikawa, Masafusa Onoue, Yoshiki Matsuoka, Takuma Izumi, Michael A. Strauss, Seiji Fujimoto, Masatoshi Imanishi, Kei Ito, Kazushi Iwasawa, Toshihiro Kawaguchi, Chien Hsiu Lee, Yongming Liang, Ting Yi Lu, Rieko Momose, Yoshiki Toba, Hisakazu Uchiyama

    Astrophysical Journal   903 ( 1 )  2020.11

     View Summary

    We present measurements of the size of the quasar proximity zone (Rp) for 11 low-luminosity (-26.16 ≤ M1450 ≤ -22.83) quasars at z ∼ 6, discovered by the Subaru High-z Exploration of Low-Luminosity Quasars project. Our faint quasar sample expands the Rp measurement down to M1450 = -22.83 mag, where more common quasar populations dominate at the epoch. We restrict the sample to quasars whose systemic redshifts have been precisely measured by [C II] 158 μm or Mg II λ2798 emission lines. We also update the Rp measurements for 26 luminous quasars presented in Eilers et al. by using the latest systemic redshift results. The luminosity dependence on Rp is found to be consistent with the theoretical prediction assuming a highly ionized intergalactic medium. We find a shallow redshift evolution of the luminosity-corrected Rp, Rp-,corr25 (Rp-,corr25 µ (1 + z)-3.79±1.72) over 5.8 ≤ z ≤ 6.6. This trend is steeper than that of Eilers et al., but significantly shallower than those of the earlier studies. Our results suggest that Rp,corr is insensitive to the neutral fraction of the universe at z ∼ 6. Four quasars show exceptionally small Rp-,corr25 (≤0.90 proper Mpc), which could be the result of their young age (<104 yr) in the reionization epoch, though statistics on this are still scarce.

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  • Probing the nature of high-redshift weak emission line quasars: A young quasar with a starburst host galaxy

    Irham Taufik Andika, Knud Jahnke, Masafusa Onoue, Eduardo Bañados, Chiara Mazzucchelli, Mladen Novak, Anna Christina Eilers, Bram P. Venemans, Jan Torge Schindler, Fabian Walter, Marcel Neeleman, Robert A. Simcoe, Roberto Decarli, Emanuele Paolo Farina, Victor Marian, Antonio Pensabene, Thomas M. Cooper, Alejandra F. Rojas

    Astrophysical Journal   903 ( 1 )  2020.11

     View Summary

    We present the discovery of PSO J083.8371+11.8482, a weak emission line quasar with extreme star formation rate at z = 6.3401. This quasar was selected from Pan-STARRS1, UHS, and unWISE photometric data. Gemini/ GNIRS spectroscopy follow-up indicates a Mg II-based black hole mass of MBH = (2.0-+0.40.7) ´ 109 Me and an Eddington ratio of Lbol LEdd = 0.5-+0.20.1, in line with an actively accreting supermassive black hole (SMBH) at z ≥ 6. Hubble Space Telescope imaging sets strong constraint on lens boosting, showing no relevant effect on the apparent emission. The quasar is also observed as a pure point source with no additional emission component. The broad-line region (BLR) emission is intrinsically weak and not likely caused by an intervening absorber. We found rest-frame equivalent widths of EW (Lya + N V)rest = 5.7 ± 0.7 Å, EW (C IV)rest ≤ 5.8 Å (3σ upper limit), and EW (Mg II)rest = 8.7 ± 0.7 Å. A small proximity zone size (Rp = 1.2 ± 0.4 pMpc) indicates a lifetime of only tQ = 103.4±0.7 years from the last quasar phase ignition. ALMA shows extended [C II] emission with a mild velocity gradient. The inferred far-infrared luminosity (LFIR = (1.2 ± 0.1) ´ 1013 L◦) is one of the highest among all known quasar hosts at z ≥ 6. Dust and [C II] emissions put a constraint on the star formation rate of SFR = 900–4900 M◦ yr-1, similar to that of a hyperluminous infrared galaxy. Considering the observed quasar lifetime and BLR formation timescale, the weak-line profile in the quasar spectrum is most likely caused by a BLR that is not yet fully formed rather than by continuum boosting by gravitational lensing or a soft continuum due to super-Eddington accretion.

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  • The UV Luminosity Function of Protocluster Galaxies at z ∼ 4: The Bright-end Excess and the Enhanced Star Formation Rate Density

    Kei Ito, Nobunari Kashikawa, Jun Toshikawa, Roderik Overzier, Mariko Kubo, Hisakazu Uchiyama, Yongming Liang, Masafusa Onoue, Masayuki Tanaka, Yutaka Komiyama, Chien Hsiu Lee, Yen Ting Lin, Murilo Marinello, Crystal L. Martin, Takatoshi Shibuya

    Astrophysical Journal   899 ( 1 )  2020.08

     View Summary

    We report the rest-frame ultraviolet luminosity function of g-dropout galaxies in 177 protocluster candidates (PC UVLF) at z ∼ 4 selected in the Hyper Suprime-Cam Subaru Strategic Program. Comparing it with the UVLF of field galaxies at the same redshift, we find that the PC UVLF shows a significant excess toward the bright end. This excess cannot be explained by the contribution of only active galactic nuclei, and we also find that this excess is more significant in higher density regions. Assuming that all protocluster members are located on the star formation main sequence, the PC UVLF can be converted into a stellar mass function. Consequently, our protocluster members are inferred to have a 2.8 times more massive characteristic stellar mass than that of the field Lyman break galaxies at the same redshift. This study, for the first time, clearly shows that the enhancement in star formation or stellar mass in overdense regions can generally be seen as early as at z ∼ 4. We also estimate the star formation rate density (SFRD) in protocluster regions as ≃6%-20% of the cosmic SFRD, based on the measured PC UVLF after correction for the selection incompleteness in our protocluster sample. This high value suggests that protoclusters make a nonnegligible contribution to the cosmic SFRD at z ∼ 4, as previously suggested by simulations. Our results suggest that protoclusters are essential components for galaxy evolution at z ∼ 4.

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  • No Redshift Evolution in the Broad-line-region Metallicity up to z = 7.54: Deep Near-infrared Spectroscopy of ULAS J1342+0928

    Masafusa Onoue, Eduardo Bañados, Chiara Mazzucchelli, Bram P. Venemans, Jan Torge Schindler, Fabian Walter, Joseph F. Hennawi, Irham Taufik Andika, Frederick B. Davies, Roberto Decarli, Emanuele P. Farina, Knud Jahnke, Tohru Nagao, Nozomu Tominaga, Feige Wang

    Astrophysical Journal   898 ( 2 )  2020.08

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    We present deep (9 hr) Gemini-N/Gemini Near-InfraRed Spectrograph near-infrared spectroscopic observations of ULAS J1342+0928, a luminous quasar at z = 7.54. Various broad emission lines were detected, as well as the underlying continuum and iron forests over the rest-frame wavelength 970-2930 Å. There is a clear trend that higher-ionization emission lines show larger blueshifts with C IV λ 1549 exhibiting 5510110240 km s-1 blueshift with respect to the systematic redshift from the far-infrared [C ii] 158μm emission line. Those high-ionization lines have wide profiles with FWHM more than 10,000 km s-1. A modest blueshift of 34080110 km s-1 is also seen in Mg ii, the lowest-ionization line identified in the spectrum. The updated Mg ii-based black hole mass of MBH=9.1-1.31.4 × 108M⊙ and the Eddington ratio of Lbol/LEdd = 1.1-0.2+0.2 confirm that ULAS J1342+0928 is powered by a massive and actively accreting black hole. There is no significant difference in the emission-line ratios such as Si iv/C iv and Al iii/C iv when compared to lower-redshift quasars in a similar luminosity range, which suggests early metal pollution of the broad-line-region clouds. This trend also holds for the Fe ii/Mg ii line ratio, known as a cosmic clock that traces the iron enrichment in the early universe. Different iron templates and continuum fitting ranges were used to explore how the Fe ii/Mg ii measurement changes as a function of spectral modeling. Quasars at even higher redshift or at fainter luminosity range (Lbol/LEdd≲ 1046 erg s-1) are needed to probe the sites of early metal enrichment and a corresponding change in the Fe ii/Mg ii ratio.

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  • Rapid evolution and transformation into quiescence?: ALMA view on z &gt; 6 low-luminosity quasars

    Izumi, T., Onoue, M., Matsuoka, Y., Nagao, T., Strauss, M.A., Imanishi, M., Kashikawa, N., Fujimoto, S., Kohno, K., Toba, Y., Umehata, H., Goto, T., Ueda, Y., Shirakata, H., Silverman, J.D., Greene, J.E., Harikane, Y., Hashimoto, Y., Ikarashi, S., Iono, D., Iwasawa, K., Lee, C.-H., Minezaki, T., Nakanishi, K., Tamura, Y., Tang, J.-J., Taniguchi, A.

    Proceedings of the International Astronomical Union    2020

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  • The ionized- And cool-gas content of the BR1202-0725 system as seen by MUSE and ALMA

    Drake, A.B., Walter, F., Novak, M., Farina, E.P., Neeleman, M., Riechers, D., Carilli, C., Decarli, R., Mazzucchelli, C., Onoue, M.

    Astrophysical Journal   902 ( 1 )  2020

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  • Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IX. Identification of two red quasars at z &gt; 5.6

    KATO, N., MATSUOKA, Y., ONOUE, M., KOYAMA, S., TOBA, Y., AKIYAMA, M., FUJIMOTO, S., IMANISHI, M., IWASAWA, K., IZUMI, T., KASHIKAWA, N., KAWAGUCHI, T., LEE, C.-H., MINEZAKI, T., NAGAO, T., NOBORIGUCHI, A., STRAUSS, M.A.

    Publications of the Astronomical Society of Japan   72 ( 5 )  2020

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  • Dual Supermassive Black Holes at Close Separation Revealed by the Hyper Suprime-Cam Subaru Strategic Program

    Silverman, J.D., Tang, S., Lee, K.-G., Hartwig, T., Goulding, A., Strauss, M.A., Schramm, M., Ding, X., Riffel, R.A., Fujimoto, S., Hikage, C., Imanishi, M., Iwasawa, K., Jahnke, K., Kayo, I., Kashikawa, N., Kawaguchi, T., Kohno, K., Luo, W., Matsuoka, Y., Matsuda, Y., Nagao, T., Oguri, M., Ono, Y., Onoue, M., Ouchi, M., Shimasaku, K., Suh, H., Suzuki, N., Taniguchi, Y., Toba, Y., Ueda, Y., Yasuda, N.

    Astrophysical Journal   899 ( 2 )  2020

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  • A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with the Lyman Break Technique

    Yamashita, T., Nagao, T., Ikeda, H., Toba, Y., Kajisawa, M., Ono, Y., Tanaka, M., Akiyama, M., Harikane, Y., Ichikawa, K., Kawaguchi, T., Kawamuro, T., Kohno, K., Lee, C.-H., Lee, K., Matsuoka, Y., Niida, M., Ogura, K., Onoue, M., Uchiyama, H.

    Astronomical Journal   160 ( 2 )  2020

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  • A Significant Excess in Major Merger Rate for AGNs with the Highest Eddington Ratios at z &lt; 0.2

    Marian, V., Jahnke, K., Andika, I., Baados, E., Bennert, V.N., Cohen, S., Husemann, B., Kaasinen, M., Koekemoer, A.M., Mechtley, M., Onoue, M., Schindler, J.-T., Schramm, M., Schulze, A., Silverman, J.D., Smirnova-Pinchukova, I., d, Wel, A.V.D., Villforth, C., Windhorst, R.A.

    Astrophysical Journal   904 ( 1 )  2020

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  • Subaru high-Z exploration of Low-luminosity quasars (ShellQs). VIII. A less biased view of the early co-evolution of black holes and host galaxies

    Takuma Izumi, Masafusa Onoue, Yoshiki Matsuoka, Tohru Nagao, Michael A. Strauss, Masatoshi Imanishi, Nobunari Kashikawa, Seiji Fujimoto, Kotaro Kohno, Yoshiki Toba, Hideki Umehata, Tomotsugu Goto, Yoshihiro Ueda, Hikari Shirakata, John D. Silverman, Jenny E. Greene, Yuichi Harikane, Yasuhiro Hashimoto, Soh Ikarashi, Daisuke Iono, Kazushi Iwasawa, Chien Hsiu Lee, Takeo Minezaki, Kouichiro Nakanishi, Yoichi Tamura, Ji Jia Tang, Akio Taniguchi

    Publications of the Astronomical Society of Japan   71 ( 6 )  2019.12

     View Summary

    We present ALMA [C II] line and far-infrared (FIR) continuum observations of three z > 6 low-luminosity quasars (M1450 > –25 mag) discovered by our Subaru Hyper Suprime-Cam (HSC) survey. The [C II] line was detected in all three targets with luminosities of (2.4–9.5) × 108 L⊙, about one order of magnitude smaller than optically luminous (M1450 ≲ –25 mag) quasars. The FIR continuum luminosities range from < 9 × 1010 L⊙ (3 σ limit) to ∼2 × 1012 L⊙, indicating a wide range in star formation rates in these galaxies. Most of the HSC quasars studied thus far show [C II]/FIR luminosity ratios similar to local star-forming galaxies. Using the [C II]-based dynamical mass (Mdyn) as a surrogate for bulge stellar mass (Mbulge), we find that a significant fraction of low-luminosity quasars are located on or even below the local MBH–Mbulge relation, particularly at the massive end of the galaxy mass distribution. In contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. Given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. Almost all of the quasars presented in this work are growing their black hole mass at a much higher pace at z ∼ 6 than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local MBH–Mbulge relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at z ∼ 6, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). X. Discovery of 35 Quasars and Luminous Galaxies at 5.7 ≤ z ≤ 7.0

    Yoshiki Matsuoka, Kazushi Iwasawa, Masafusa Onoue, Nobunari Kashikawa, Michael A. Strauss, Chien Hsiu Lee, Masatoshi Imanishi, Tohru Nagao, Masayuki Akiyama, Naoko Asami, James Bosch, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Takuma Izumi, Toshihiro Kawaguchi, Nanako Kato, Satoshi Kikuta, Kotaro Kohno, Yutaka Komiyama, Shuhei Koyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Hitoshi Murayama, Mana Niida, Atsushi J. Nishizawa, Akatoki Noboriguchi, Masamune Oguri, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, Andreas Schulze, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Ji Jia Tang, Yoshiki Toba, Yousuke Utsumi, Shiang Yu Wang, Takuji Yamashita

    Astrophysical Journal   883 ( 2 )  2019.10

     View Summary

    We report the discovery of 28 quasars and 7 luminous galaxies at 5.7 ≤ z ≤ 7.0. This is the tenth in a series of papers from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the deep multiband imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The total number of spectroscopically identified objects in SHELLQs has now grown to 93 high-z quasars, 31 high-z luminous galaxies, 16 [O iii] emitters at z ∼ 0.8, and 65 Galactic cool dwarfs (low-mass stars and brown dwarfs). These objects were found over 900 deg2, surveyed by HSC between 2014 March and 2018 January. The full quasar sample includes 18 objects with very strong and narrow Lyα emission, whose stacked spectrum is clearly different from that of other quasars or galaxies. While the stacked spectrum shows N v λ1240 emission and resembles that of lower-z narrow-line quasars, the small Lyα width may suggest a significant contribution from the host galaxies. Thus, these objects may be composites of quasars and star-forming galaxies.

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  • The Brightest UV-selected Galaxies in Protoclusters at z ∼ 4: Ancestors of Brightest Cluster Galaxies?

    Kei Ito, Nobunari Kashikawa, Jun Toshikawa, Roderik Overzier, Masayuki Tanaka, Mariko Kubo, Takatoshi Shibuya, Shogo Ishikawa, Masafusa Onoue, Hisakazu Uchiyama, Yongming Liang, Ryo Higuchi, Crystal L. Martin, Chien Hsiu Lee, Yutaka Komiyama, Song Huang

    Astrophysical Journal   878 ( 1 )  2019.06

     View Summary

    We present the results of a survey of the brightest UV-selected galaxies in protoclusters. These proto-brightest cluster galaxy (proto-BCG) candidates are drawn from 179 overdense regions of g-dropout galaxies at z ∼ 4 from the Hyper Suprime-Cam Subaru Strategic Program identified previously as good protocluster candidates. This study is the first to extend the systematic study of the progenitors of BCGs from z ∼ 2 to z ∼ 4. We carefully remove possible contaminants from foreground galaxies and, for each structure, select the brightest galaxy that is at least 1 mag brighter than the fifth-brightest galaxy. We select 63 proto-BCG candidates and compare their properties with those of galaxies in the field and those of other galaxies in overdense structures. The proto-BCG candidates and their surrounding galaxies have different rest-UV color (i - z) distributions to field galaxies and other galaxies in protoclusters that do not host proto-BCGs. In addition, galaxies surrounding proto-BCGs are brighter than those in protoclusters without proto-BCGs. The image stacking analysis reveals that the average effective radius of proto-BCGs is ∼28% larger than that of field galaxies. The i - z color differences suggest that proto-BCGs and their surrounding galaxies are dustier than other galaxies at z ∼ 4. These results suggest that specific environmental effects or assembly biases have already emerged in some protoclusters as early as z ∼ 4, and we suggest that proto-BCGs have different star formation histories than other galaxies in the same epoch.

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  • Discovery of the First Low-luminosity Quasar at z &gt; 7

    Yoshiki Matsuoka, Masafusa Onoue, Nobunari Kashikawa, Michael A. Strauss, Kazushi Iwasawa, Chien Hsiu Lee, Masatoshi Imanishi, Tohru Nagao, Masayuki Akiyama, Naoko Asami, James Bosch, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Takuma Izumi, Toshihiro Kawaguchi, Nanako Kato, Satoshi Kikuta, Kotaro Kohno, Yutaka Komiyama, Shuhei Koyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Hitoshi Murayama, Mana Niida, Atsushi J. Nishizawa, Akatoki Noboriguchi, Masamune Oguri, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, Andreas Schulze, Hikari Shirakata, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Ji Jia Tang, Yoshiki Toba, Yousuke Utsumi, Shiang Yu Wang, Takuji Yamashita

    Astrophysical Journal Letters   872 ( 1 )  2019.02

     View Summary

    We report the discovery of a quasar at z = 7.07, which was selected from the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. This quasar, HSC J124353.93+010038.5, has an order of magnitude lower luminosity than do the other known quasars at z > 7. The rest-frame ultraviolet absolute magnitude is M 1450 = -24.13 0.08 mag and the bolometric luminosity is erg s -1 . Its spectrum in the optical to near-infrared shows strong emission lines, and shows evidence for a fast gas outflow, as the C iv line is blueshifted and there is indication of broad absorption lines. The Mg ii-based black hole mass is , thus indicating a moderate mass accretion rate with an Eddington ratio . It is the first z > 7 quasar with sub-Eddington accretion, besides being the third most distant quasar known to date. The luminosity and black hole mass are comparable to, or even lower than, those measured for the majority of low-z quasars discovered by the Sloan Digital Sky Survey, and thus this quasar likely represents a z > 7 counterpart to quasars commonly observed in the low-z universe.

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  • Optical Properties of Infrared-bright Dust-obscured Galaxies Viewed with Subaru Hyper Suprime-Cam

    Noboriguchi, A., Nagao, T., Toba, Y., Niida, M., Kajisawa, M., Onoue, M., Matsuoka, Y., Yamashita, T., Chang, Y.-Y., Kawaguchi, T., Komiyama, Y., Nobuhara, K., Terashima, Y., Ueda, Y.

    Astrophysical Journal   876 ( 2 )  2019

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  • The REQUIEM Survey. I. A Search for Extended Lyα Nebular Emission around 31 z &gt; 5.7 Quasars

    Farina, E.P., Arrigoni-Battaia, F., Costa, T., Walter, F., Hennawi, J.F., Drake, A.B., Decarli, R., Gutcke, T.A., Mazzucchelli, C., Neeleman, M., Georgiev, I., Eilers, A.-C., Davies, F.B., Ba\&amp, ntilde, ados, E., Fan, X., Onoue, M., Schindler, J.-T., Venemans, B.P., Wang, F., Yang, J., Rabien, S., Busoni, L.

    Astrophysical Journal   887 ( 2 )  2019

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

    Aihara, H., Alsayyad, Y., Ando, M., Armstrong, R., Bosch, J., Egami, E., Furusawa, H., Furusawa, J., Goulding, A., Harikane, Y., Hikage, C., Ho, P.T.P., Hsieh, B.-C., Huang, S., Ikeda, H., Imanishi, M., Ito, K., Iwata, I., Jaelani, A.T., Kakuma, R., Kawana, K., Kikuta, S., Kobayashi, U., Koike, M., Komiyama, Y., Li, X., Liang, Y., Lin, Y.-T., Luo, W., Lupton, R., Lust, N.B., Macarthur, L.A., Matsuoka, Y., Mineo, S., Miyatake, H., Miyazaki, S., More, S., Murata, R., Namiki, S.V., Nishizawa, A.J., Oguri, M., Okabe, N., Okamoto, S., Okura, Y., Ono, Y., Onodera, M., Onoue, M., Osato, K., Ouchi, M., Shibuya, T., Strauss, M.A., Sugiyama, N., Suto, Y., Takada, M., Takagi, Y., Takata, T., Takita, S., Tanaka, M., Terai, T., Toba, Y., Uchiyama, H., Utsumi, Y., Wang, S.-Y., Wang, W., Yamada, Y.

    Publications of the Astronomical Society of Japan   71 ( 6 )  2019

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  • A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). II. Physical Properties Derived from the SED Fitting with Optical, Infrared, and Radio Data

    Toba, Y., Yamashita, T., Nagao, T., Wang, W.-H., Ueda, Y., Ichikawa, K., Kawaguchi, T., Akiyama, M., Hsieh, B.-C., Kajisawa, M., Lee, C.-H., Matsuoka, Y., Noboriguchi, A., Onoue, M., Schramm, M., Tanaka, M., Komiyama, Y.

    Astrophysical Journal, Supplement Series   243 ( 1 )  2019

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  • Suppression of Low-mass Galaxy Formation around Quasars at z ∼ 2-3

    Hisakazu Uchiyama, Nobunari Kashikawa, Roderik Overzier, Jun Toshikawa, Masafusa Onoue, Shogo Ishikawa, Mariko Kubo, Kei Ito, Shigeru Namiki, Yongming Liang

    Astrophysical Journal   870 ( 1 )  2019.01

     View Summary

    We have carried out deep and wide field imaging observations with narrow bands, targeting 11 quasar fields to systematically study the possible photoevaporation effect of quasar radiation on surrounding low mass galaxies at z ∼ 2-3. We focused on Lyα emitters (LAEs) at the same redshifts as quasars that lie within the quasar proximity zones, where the UV radiation from the quasars is higher than the average background at that epoch. We found that LAEs with high rest-frame equivalent width of Lyα emission (EW0) of ≳150 Å with low stellar mass (≲108 M o) are predominantly scarce in the quasar proximity zones, suggesting that quasar photoevaporation effects may be taking place. The halo mass of LAEs with EW0 > 150 Å is estimated to be either from spectral energy distribution fitting or the main sequence. Based on a hydrodynamical simulation, the predicted delay in star formation under a local UV background intensity with erg s-1 cm-2 Hz-1 sr-1 for galaxies having less than this halo mass is about >20 Myr, which is longer than the expected age of LAEs with EW0 > 150 Å. On the other hand, photoevaporation seems to be less effective around very luminous quasars, which is consistent with the idea that these are still in an early stage of activity.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6

    Yoshiki Matsuoka, Michael A. Strauss, Nobunari Kashikawa, Masafusa Onoue, Kazushi Iwasawa, Ji Jia Tang, Chien Hsiu Lee, Masatoshi Imanishi, Tohru Nagao, Masayuki Akiyama, Naoko Asami, James Bosch, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Takuma Izumi, Toshihiro Kawaguchi, Nanako Kato, Satoshi Kikuta, Kotaro Kohno, Yutaka Komiyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Hitoshi Murayama, Mana Niida, Atsushi J. Nishizawa, Akatoki Noboriguchi, Masamune Oguri, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, Andreas Schulze, Hikari Shirakata, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Yoshiki Toba, Yousuke Utsumi, Shiang Yu Wang, Takuji Yamashita

    Astrophysical Journal   869 ( 2 )  2018.12

     View Summary

    We present new measurements of the quasar luminosity function (LF) at z ∼ 6 over an unprecedentedly wide range of the rest-frame ultraviolet luminosity M 1450 from -30 to -22 mag. This is the fifth in a series of publications from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the deep multiband imaging data produced by the Hyper Suprime-Cam Subaru Strategic Program survey. The LF was calculated with a complete sample of 110 quasars at 5.7 ≤ z ≤ 6.5, which includes 48 SHELLQs quasars discovered over 650 deg2 and 63 brighter quasars discovered by the Sloan Digital Sky Survey and the Canada-France-Hawaii Quasar Survey (including one overlapping object). This is the largest sample of z ∼ 6 quasars with a well-defined selection function constructed to date, which has allowed us to detect significant flattening of the LF at its faint end. A double power-law function fit to the sample yields a faint-end slope , a bright-end slope , a break magnitude , and a characteristic space density Gpc-3 mag-1. Integrating this best-fit model over the range -18 < M 1450 < -30 mag, quasars emit ionizing photons at the rate of s-1 Mpc-3 at z = 6.0. This is less than 10% of the critical rate necessary to keep the intergalactic medium ionized, which indicates that quasars are not a major contributor to cosmic reionization.

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  • Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 ≤ z ≤ 6.9

    Yoshiki Matsuoka, Kazushi Iwasawa, Masafusa Onoue, Nobunari Kashikawa, Michael A. Strauss, Chien Hsiu Lee, Masatoshi Imanishi, Tohru Nagao, Masayuki Akiyama, Naoko Asami, James Bosch, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Takuma Izumi, Toshihiro Kawaguchi, Nanako Kato, Satoshi Kikuta, Kotaro Kohno, Yutaka Komiyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Tomoki Morokuma, Hitoshi Murayama, Mana Niida, Atsushi J. Nishizawa, Masamune Oguri, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, Andreas Schulze, Hikari Shirakata, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Ji Jia Tang, Yoshiki Toba, Yousuke Utsumi, Shiang Yu Wang, Takuji Yamashita

    Astrophysical Journal, Supplement Series   237 ( 1 )  2018.07

     View Summary

    We report the discovery of 41 new high-z quasars and luminous galaxies that were spectroscopically identified at 5.7 ≤ z ≤ 6.9. This is the fourth in a series of papers from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, based on the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We selected the photometric candidates using a Bayesian probabilistic algorithm and then carried out follow-up spectroscopy with the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous papers, we have now spectroscopically identified 137 extremely red HSC sources over about 650 deg2, which includes 64 high-z quasars, 24 high-z luminous galaxies, 6 [O iii] emitters at z ∼ 0.8, and 43 Galactic cool dwarfs (low-mass stars and brown dwarfs). The new quasars span in luminosity range from M 1450 ∼ -26 to -22 mag, and continue to populate luminosities a few magnitudes lower than have been probed by previous wide-field surveys. In a companion paper, we derive the quasar luminosity function at z ∼ 6 over an unprecedentedly wide range of M 1450 ∼ -28 to -21 mag, exploiting the SHELLQs and other survey outcomes.

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  • Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ∼ 6 studied with ALMA

    Takuma Izumi, Masafusa Onoue, Hikari Shirakata, Tohru Nagao, Kotaro Kohno, Yoshiki Matsuoka, Masatoshi Imanishi, Michael A. Strauss, Nobunari Kashikawa, Andreas Schulze, John D. Silverman, Seiji Fujimoto, Yuichi Harikane, Yoshiki Toba, Hideki Umehata, Kouichiro Nakanishi, Jenny E. Greene, Yoichi Tamura, Akio Taniguchi, Yuki Yamaguchi, Tomotsugu Goto, Yasuhiro Hashimoto, Soh Ikarashi, Daisuke Iono, Kazushi Iwasawa, Chien Hsiu Lee, Ryu Makiya, Takeo Minezaki, Ji Jia Tang

    Publications of the Astronomical Society of Japan   70 ( 3 )  2018.06

     View Summary

    We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L[C II] = (3.8-10.2) × 108 L· and LFIR = (1.2-2.0) × 1011 L·, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≲ 23-40 M· yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L[C II]/LFIR ratios of the hosts, ≲ (2.2- 8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≲ (1.4-8.2) × 1010 M·. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ∼ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

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    59
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  • The Hyper Suprime-Cam SSP survey: Overview and survey design

    Aihara, H., Arimoto, N., Armstrong, R., Arnouts, S., Bahcall, N.A., Bickerton, S., Bosch, J., Bundy, K., Capak, P.L., Chan, J.H.H., Chiba, M., Coupon, J., Egami, E., Enoki, M., Finet, F., Fujimori, H., Fujimoto, S., Furusawa, H., Furusawa, J., Goto, T., Goulding, A., Greco, J.P., Greene, J.E., Gunn, J.E., Hamana, T., Harikane, Y., Hashimoto, Y., Hattori, T., Hayashi, M., Hayashi, Y., He?miniak, K.G., Higuchi, R., Hikage, C., Ho, P.T.P., Hsieh, B.-C., Huang, K., Huang, S., Ikeda, H., Imanishi, M., Inoue, A.K., Iwasawa, K., Iwata, I., Jaelani, A.T., Jian, H.-Y., Kamata, Y., Karoji, H., Kashikawa, N., Katayama, N., Kawanomoto, S., Kayo, I., Koda, J., Koike, M., Kojima, T., Komiyama, Y., Konno, A., Koshida, S., Koyama, Y., Kusakabe, H., Leauthaud, A., Lee, C.-H., Lin, L., Lin, Y.-T., Lupton, R.H., Mandelbaum, R., Matsuoka, Y., Medezinski, E., Mineo, S., Miyama, S., Miyatake, H., Miyazaki, S., Momose, R., More, A., More, S., Moritani, Y., Oriya, T.J., M, Morokuma, T., Mukae, S., Murata, R., Murayama, H., Nagao, T., Nakata, F., Niida, M., Niikura, H., Nishizawa, A.J., Obuchi, Y., Oguri, M., Oishi, Y., Okabe, N., Okamoto, S., Okura, Y., Ono, Y., Onodera, M., Onoue, M., Osato, K., Ouchi, M., Price, P.A., Pyo, T.-S., Sako, M., Sawicki, M., Shibuya, T., Shimasaku, K., Shimono, A., Shirasaki, M., Silverman, J.D., Simet, M., Speagle, J., Spergel, D.N., Strauss, M.A., Sugahara, Y., Sugiyama, N., Suto, Y., Suyu, S.H., Suzuki, N., Tait, P.J., Takada, M., Takata, T., Tamura, N., Tanaka, M.M., Tanaka, M., Tanaka, M., Tanaka, Y., Terai, T., Terashima, Y., Toba, Y., Tominaga, N., Toshikawa, J., Turner, E.L., Uchida, T., Uchiyama, H., Umetsu, K., Uraguchi, F., Urata, Y.J., Usuda, T., Utsumi, Y., Wang, S.-Y., Wang, W.-H., Wong, K.C., Yabe, K., Yamada, Y., Yamanoi, H., Yasuda, N., Yeh, S., Yonehara, A., Yuma, S.

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018

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

    Aihara, H., Armstrong, R., Bickerton, S., Bosch, J., Coupon, J., Furusawa, H., Hayashi, Y., Ikeda, H., Kamata, Y., Karoji, H., Kawanomoto, S., Koike, M., Komiyama, Y., Lang, D., Lupton, R.H., Mineo, S., Miyatake, H., Miyazaki, S., Morokuma, T., Obuchi, Y., Oishi, Y., Okura, Y., Price, P.A., Takata, T., Tanaka, M.M., Tanaka, M., Tanaka, Y., Uchida, T., Uraguchi, F., Utsumi, Y., Wang, S.-Y., Yamada, Y., Yamanoi, H., Yasuda, N., Arimoto, N., Chiba, M., Finet, F., Fujimori, H., Fujimoto, S., Furusawa, J., Goto, T., Goulding, A., Gunn, J.E., Harikane, Y., Hattori, T., Hayashi, M., Helminiak, K.G., Higuchi, R., Hikage, C., Ho, P.T.P., Hsieh, B.-C., Huang, K., Huang, S., Imanishi, M., Iwata, I., Jaelani, A.T., Jian, H.-Y., Kashikawa, N., Katayama, N., Kojima, T., Konno, A., Koshida, S., Kusakabe, H., Leauthaud, A., Lee, C.-H., Lin, L., Lin, Y.-T., Mandelbaum, R., Matsuoka, Y., Medezinski, E., Miyama, S., Momose, R., More, A., More, S., Mukae, S., Murata, R., Murayama, H., Nagao, T., Nakata, F., Niida, M., Niikura, H., Nishizawa, A.J., Oguri, M., Okabe, N., Ono, Y., Onodera, M., Onoue, M., Ouchi, M., Pyo, T.-S., Shibuya, T., Shimasaku, K., Simet, M., Speagle, J., Spergel, D.N., Strauss, M.A., Sugahara, Y., Sugiyama, N., Suto, Y., Suzuki, N., Tait, P.J., Takada, M., Terai, T., Toba, Y., Turner, E.L., Uchiyama, H., Umetsu, K., Urata, Y., Usuda, T., Yeh, S., Yuma, S.

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018

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  • Luminous quasars do not live in the most overdense regions of galaxies at z ∼ 4

    Hisakazu Uchiyama, Jun Toshikawa, Nobunari Kashikawa, Roderik Overzier, Yi Kuan Chiang, Murilo Marinello, Masayuki Tanaka, Yuu Niino, Shogo Ishikawa, Masafusa Onoue, Kohei Ichikawa, Masayuki Akiyama, Jean Coupon, Yuichi Harikane, Masatoshi Imanishi, Tadayuki Kodama, Yutaka Komiyama, Chien Hsiu Lee, Yen Ting Lin, Satoshi Miyazaki, Tohru Nagao, Atsushi J. Nishizawa, Yoshiaki Ono, Masami Ouchi, Shiang Yu Wang

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We present the cross-correlation between 151 luminous quasars (MUV < -26) and 179 protocluster candidates at z ∼ 3.8, extracted from the Wide imaging survey (∼121 deg2) performed as part of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We find that only two out of 151 quasars reside in regions that are more overdense compared to the average field at >4 σ. The distributions of the distances between quasars and the nearest protoclusters and the significance of the overdensity at the positions of quasars are statistically identical to those found for g-dropout galaxies, suggesting that quasars tend to reside in almost the same environment as star-forming galaxies at this redshift. Using stacking analysis, we find that the average density of g-dropout galaxies around quasars is slightly higher than that around g-dropout galaxies on 1.0-2.5 pMpc scales, while at <0.5 pMpc that around quasars tends to be lower. We also find that quasars with higher UV luminosity or with more massive black holes tend to avoid the most overdense regions, and that the quasar near-zone sizes are anti-correlated with overdensity. These findings are consistent with a scenario in which luminous quasars at z ∼ 4 reside in structures that are less massive than those expected for the progenitors of today's rich clusters of galaxies, and possibly that luminous quasarsmay be suppressing star formation in their close vicinity.

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  • Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam Wide-field imaging

    Wanqiu He, Masayuki Akiyama, James Bosch, Motohiro Enoki, Yuichi Harikane, Hiroyuki Ikeda, Nobunari Kashikawa, Toshihiro Kawaguchi, Yutaka Komiyama, Chien Hsiu Lee, Yoshiki Matsuoka, Satoshi Miyazaki, Tohru Nagao, Masahiro Nagashima, Mana Niida, Atsushi J. Nishizawa, Masamune Oguri, Masafusa Onoue, Taira Oogi, Masami Ouchi, Andreas Schulze, Yuji Shirasaki, John D. Silverman, Manobu M. Tanaka, Masayuki Tanaka, Yoshiki Toba, Hisakazu Uchiyama, Takuji Yamashita

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We examine the clustering of quasars over a wide luminosity range, by utilizing 901 quasars at zphot ∼ 3.8 with -24.73 < M1450 < -22.23 photometrically selected from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) S16A Wide2 date release and 342 more luminous quasars at 3.4 < zspec < 4.6 with -28.0 < M1450 < -23.95 from the Sloan Digital Sky Survey that fall in the HSC survey fields. We measure the bias factors of two quasar samples by evaluating the cross-correlation functions (CCFs) between the quasar samples and 25790 bright z ∼ 4 Lyman break galaxies in M1450 < -21.25 photometrically selected from the HSC dataset. Over an angular scale of 10.0 to 1000.0, the bias factors are 5.93+1.34 -1.43 and 2.73+2.44 -2.55 for the low- and high-luminosity quasars, respectively, indicating no significant luminosity dependence of quasar clustering at z ∼ 4. It is noted that the bias factor of the luminous quasars estimated by the CCF is smaller than that estimated by the auto-correlation function over a similar redshift range, especially on scales below 40.0. Moreover, the bias factor of the less-luminous quasars implies the minimal mass of their host dark matter halos is 0.3-2 × 1012 h-1M, corresponding to a quasar duty cycle of 0.001-0.06.

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    43
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  • The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

    Masayuki Akiyama, Wanqiu He, Hiroyuki Ikeda, Mana Niida, Tohru Nagao, James Bosch, Jean Coupon, Motohiro Enoki, Masatoshi Imanishi, Nobunari Kashikawa, Toshihiro Kawaguchi, Yutaka Komiyama, Chien Hsiu Lee, Yoshiki Matsuoka, Satoshi Miyazaki, Atsushi J. Nishizawa, Masamune Oguri, Yoshiaki Ono, Masafusa Onoue, Masami Ouchi, Andreas Schulze, John D. Silverman, Manobu M. Tanaka, Masayuki Tanaka, Yuichi Terashima, Yoshiki Toba, Yoshihiro Ueda

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We present the luminosity function of z ∼ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ∼ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36±0.13mag and a flat faint-end slope with a power-law index of -1.30±0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ∼ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

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  • Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 &lt; z ≤ 6.8

    Yoshiki Matsuoka, Masafusa Onoue, Nobunari Kashikawa, Kazushi Iwasawa, Michael A. Strauss, Tohru Nagao, Masatoshi Imanishi, Chien Hsiu Lee, Masayuki Akiyama, Naoko Asami, James Bosch, Sébastien Foucaud, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Takuma Izumi, Toshihiro Kawaguchi, Satoshi Kikuta, Kotaro Kohno, Yutaka Komiyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Tomoki Morokuma, Hitoshi Murayama, Mana Niida, Atsushi J. Nishizawa, Masamune Oguri, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, Andreas Schulze, Hikari Shirakata, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Ji Jia Tang, Yoshiki Toba, Yousuke Utsumi, Shiang Yu Wang

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 < z ≤ 6.8. This is the second in a series of papers presenting the results of the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the deep multi-band imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The photometric candidates were selected by a Bayesian probabilistic algorithm, and then observed with spectrographs on the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous paper of this series, we have now identified 64 HSC sources over about 430 deg2, which include 33 high-z quasars, 14 high-z luminous galaxies, two [OIII] emitters at z ∼ 0.8, and 15 Galactic brown dwarfs. The new quasars have considerably lower luminosity (M1450 ∼ -25 to -22 mag) than most of the previously known high-z quasars. Several of these quasars have luminous (>1043 erg s-1) and narrow (< 500kms-1) Lyα lines, and also a possible mini broad-absorption-line system of N V λ1240 in the composite spectrum, which clearly separate them from typical quasars. On the other hand, the high-z galaxies have extremely high luminosities (M1450 ∼ -24 to -22 mag) compared to other galaxies found at similar redshifts. With the discovery of these new classes of objects, we are opening up new parameter spaces in the high-z Universe. Further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ∼ 6, are ongoing.

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  • Enhancement of galaxy overdensity around quasar pairs at z &lt; 3.6 based on the Hyper Suprime-Cam Subaru Strategic Program Survey

    Masafusa Onoue, Nobunari Kashikawa, Hisakazu Uchiyama, Masayuki Akiyama, Yuichi Harikane, Masatoshi Imanishi, Yutaka Komiyama, Yoshiki Matsuoka, Tohru Nagao, Atsushi J. Nishizawa, Masamune Oguri, Masami Ouchi, Masayuki Tanaka, Yoshiki Toba, Jun Toshikawa

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We investigate the galaxy overdensity around proto-cluster scale quasar pairs at high (z > 3) and low (z ∼ 1) redshift based on the unprecedentedly wide and deep optical survey of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the firstyear survey data covering effectively ∼121 deg2 with the 5σ depth of i ∼ 26.4 and the SDSS DR12Q catalog, we find two luminous pairs at z ∼ 3.3 and 3.6 which reside in >5σ overdensity regions of g-dropout galaxies at i < 25. The projected separations of the two pairs are R = 1.75 and 1.04 proper Mpc (pMpc), and their velocity offsets are ΔV = 692 and 1448kms-1, respectively. This result is in clear contrast to the average z ∼ 4 quasar environments as discussed in Uchiyama et al. (2018, PASJ 70, S32) and implies that the quasar activities of the pair members are triggered via major mergers in proto-clusters, unlike the vast majority of isolated quasars in general fields that may turn on via non-merger events such as bar and disk instabilities. At z ∼ 1, we find 37 pairs with R < 2pMpc and ΔV < 2300kms-1 in the current HSC-Wide coverage, including four from Hennawi et al. (2006, AJ, 131, 1). The distribution of the peak overdensity significance within two arcminutes around the pairs has a long tail toward high-density (>4σ) regions. Thanks to the large sample size, we find statistical evidence that this excess is unique to the pair environments when compared to single-quasar and randomly selected galaxy environments at the same redshift range.Moreover, there are nine smallscale (R < 1 pMpc) pairs, two of which are found to reside in cluster fields. Our results demonstrate that <2 pMpc scale quasar pairs at both redshift ranges tend to occur in massive haloes, although perhaps not the most massive ones, and that they are useful in searching for rare density peaks.

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  • GOLDRUSH. III. A systematic search for protoclusters at z ∼ 4 based on the &gt;100 deg2 area

    Jun Toshikawa, Hisakazu Uchiyama, Nobunari Kashikawa, Masami Ouchi, Roderik Overzier, Yoshiaki Ono, Yuichi Harikane, Shogo Ishikawa, Tadayuki Kodama, Yuichi Matsuda, Yen Ting Lin, Masafusa Onoue, Masayuki Tanaka, Tohru Nagao, Masayuki Akiyama, Yutaka Komiyama, Tomotsugu Goto, Chien Hsiu Lee

    Publications of the Astronomical Society of Japan   70 ( Special Issue 1 )  2018.01

     View Summary

    We conduct a systematic search for galaxy protoclusters at z ∼ 3.8 based on the latest internal data release (S16A) of the Hyper Suprime-Cam Subaru strategic program (HSCSSP). In the Wide layer of the HSC-SSP, we investigate the large-scale projected sky distribution of g-dropout galaxies over an area of 121 deg2, and identify 216 large-scale overdense regions (>4 σ overdensity significance) that are likely protocluster candidates. Of these, 37 are located within 8 (3.4 physical Mpc) of other protocluster candidates of higher overdensity, and are expected to merge into a single massive structure by z = 0. Therefore, we find 179 unique protocluster candidates in our survey. A cosmological simulation that includes projection effects predicts that more than 76% of these candidates will evolve into galaxy clusters with halo masses of at least 1014 M by z = 0. The unprecedented size of our protocluster candidate catalog allows us to perform, for the first time, an angular clustering analysis of the systematic sample of protocluster candidates. We find a correlation length of 35.0 h-1 Mpc. The relation between correlation length and number density of z ∼ 3.8 protocluster candidates is consistent with the prediction of the ΣCDM model, and the correlation length is similar to that of rich clusters in the local universe. This result suggests that our protocluster candidates are tracing similar spatial structures to those expected from the progenitors of rich clusters, and enhances the confidence that our method for identifying protoclusters at high redshifts is robust. In years to come, our protocluster search will be extended to the entire HSC-SSP Wide sky coverage of ∼1400 deg2 to probe cluster formation over a wide redshift range of z ∼ 2-6.

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  • CLUSTERING of INFRARED-BRIGHT DUST-OBSCURED GALAXIES REVEALED by the HYPER SUPRIME-CAM and WISE

    Toba, Y., Nagao, T., Kajisawa, M., Oogi, T., Akiyama, M., Ikeda, H., Coupon, J., Strauss, M.A., Wang, W.-H., Tanaka, M., Niida, M., Imanishi, M., Lee, C.-H., Matsuhara, H., Matsuoka, Y., Onoue, M., Terashima, Y., Ueda, Y., Harikane, Y., Komiyama, Y., Miyazaki, S., Noboriguchi, A., Usuda, T.

    Astrophysical Journal   835 ( 1 )  2017

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  • The redshift-selected sample of long gamma-ray burst host galaxies: The overall metallicity distribution at z &lt; 0.4

    Niino, Y., Aoki, K., Hashimoto, T., Hattori, T., Ishikawa, S., Kashikawa, N., Kosugi, G., Onoue, M., Toshikawa, J., Yabe, K.

    Publications of the Astronomical Society of Japan   69 ( 2 )  2017

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  • A New Constraint on Reionization from the Evolution of the Lyα Luminosity Function at z ∼ 6-7 Probed by a Deep Census of z = 7.0 Lyα Emitter Candidates to 0.3L

    Ota, K., Iye, M., Kashikawa, N., Konno, A., Nakata, F., Totani, T., Kobayashi, M.A.R., Fudamoto, Y., Seko, A., Toshikawa, J., Ichikawa, A., Shibuya, T., Onoue, M.

    Astrophysical Journal   844 ( 1 )  2017

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  • SUBARU HIGH-z EXPLORATION of LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY of 15 QUASARS and BRIGHT GALAXIES at 5.7 &lt; z &lt; 6.9

    Yoshiki Matsuoka, Masafusa Onoue, Nobunari Kashikawa, Kazushi Iwasawa, Michael A. Strauss, Tohru Nagao, Masatoshi Imanishi, Mana Niida, Yoshiki Toba, Masayuki Akiyama, Naoko Asami, James Bosch, Sébastien Foucaud, Hisanori Furusawa, Tomotsugu Goto, James E. Gunn, Yuichi Harikane, Hiroyuki Ikeda, Toshihiro Kawaguchi, Satoshi Kikuta, Yutaka Komiyama, Robert H. Lupton, Takeo Minezaki, Satoshi Miyazaki, Tomoki Morokuma, Hitoshi Murayama, Atsushi J. Nishizawa, Yoshiaki Ono, Masami Ouchi, Paul A. Price, Hiroaki Sameshima, John D. Silverman, Naoshi Sugiyama, Philip J. Tait, Masahiro Takada, Tadafumi Takata, Masayuki Tanaka, Ji Jia Tang, Yousuke Utsumi

    Astrophysical Journal   828 ( 1 )  2016.09

     View Summary

    We report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9. This is the initial result from the Subaru High-z Exploration of Low-Luminosity Quasars project, which exploits the exquisite multiband imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg2 of the survey footprint. The success rate of our photometric selection is quite high, approaching 100% at the brighter magnitudes (zAB < 23.5 mag). Our selection also recovered all the known high-z quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-break galaxies. The remaining three objects have weak continua and very strong and narrow Lyα lines, which may be excited by ultraviolet light from both young stars and quasars. These results indicate that we are starting to see the steep rise of the luminosity function of z ≥ 6 galaxies, compared with that of quasars, at magnitudes fainter than M1450 ∼ -22 mag or zAB ∼ 24 mag. Follow-up studies of the discovered objects as well as further survey observations are ongoing.

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  • Probabilistic Selection of High-redshift Quasars with Subaru/Hyper Suprime-Cam Survey

    Masafusa Onoue

    Proceedings of the International Astronomical Union    2016

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  • The very wide-field gzK Galaxy Survey - II. The relationship between star-forming galaxies at z ~ 2 and their host haloes based upon HOD modelling

    Ishikawa, S., Kashikawa, N., Hamana, T., Toshikawa, J., Onoue, M.

    Monthly Notices of the Royal Astronomical Society   458 ( 1 )  2016

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    (Scopus)
  • A SYSTEMATIC SURVEY of PROTOCLUSTERS at z ∼ 3-6 in the CFHTLS DEEP FIELDS

    Toshikawa, J., Kashikawa, N., Overzier, R., Malkan, M.A., Furusawa, H., Ishikawa, S., Onoue, M., Ota, K., Tanaka, M., Niino, Y., Uchiyama, H.

    Astrophysical Journal   826 ( 2 )  2016

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  • A SPECTROSCOPICALLY CONFIRMED DOUBLE SOURCE PLANE LENS SYSTEM in the HYPER SUPRIME-CAM SUBARU STRATEGIC PROGRAM

    Masayuki Tanaka, Tanaka, M., Wong, K.C., More, A., Dezuka, A., Egami, E., Oguri, M., Suyu, S.H., Sonnenfeld, A., Higuchi, R., Komiyama, Y., Miyazaki, S., Onoue, M., Oyamada, S., Utsumi, Y.

    Astrophysical Journal Letters   826 ( 2 )  2016

    DOI

    Scopus

    9
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    (Scopus)
  • The very wide-field gzK galaxy survey - I. Details of the clustering properties of star-forming galaxies at z ~ 2

    Ishikawa, S., Kashikawa, N., Toshikawa, J., Onoue, M.

    Monthly Notices of the Royal Astronomical Society   454 ( 1 )  2015

    DOI

    Scopus

    18
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  • The subaru high-z quasar survey: Discovery of faint z ∼ 6 quasars

    Kashikawa, N., Ishizaki, Y., Willott, C.J., Onoue, M., Im, M., Furusawa, H., Toshikawa, J., Ishikawa, S., Niino, Y., Shimasaku, K., Ouchi, M., Hibon, P.

    Astrophysical Journal   798 ( 1 )  2015

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  • Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

    Toba, Y., Nagao, T., Strauss, M.A., Aoki, K., Goto, T., Imanishi, M., Kawaguchi, T., Terashima, Y., Ueda, Y., Bosch, J., Bundy, K., Doi, Y., Inami, H., Komiyama, Y., Lupton, R.H., Matsuhara, H., Matsuoka, Y., Miyazaki, S., Morokuma, T., Nakata, F., Oi, N., Onoue, M., Oyabu, S., Price, P., Tait, P.J., Takata, T., Tanaka, M.M., Terai, T., Turner, E.L., Uchida, T., Usuda, T., Utsumi, Y., Yamada, Y., Wang, S.-Y.

    Publications of the Astronomical Society of Japan   67 ( 5 )  2015

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  • A first site of galaxy cluster formation: Complete spectroscopy of a protocluster at z = 6.01

    Toshikawa, J., Kashikawa, N., Overzier, R., Shibuya, T., Ishikawa, S., Ota, K., Shimasaku, K., Tanaka, M., Hayashi, M., Niino, Y., Onoue, M.

    Astrophysical Journal   792 ( 1 )  2014

    DOI

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  • Extended Lyα emission from a damped Lyα absorber at z = 3.115

    Kashikawa, N., Misawa, T., Minowa, Y., Okoshi, K., Hattori, T., Toshikawa, J., Ishikawa, S., Onoue, M.

    Astrophysical Journal   780 ( 2 )  2014

    DOI

    Scopus

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Research Projects

  • Probing the origin of supermassive black holes with Subaru Telescope, JWST, and Euclid

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2024.07
    -
    2026.03
     

  • Exploration of Reionization and Supermassive Black Hole Formation through Low-Luminosity Quasar Searches at High-redshift

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2015.04
    -
    2018.03