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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

Author(s): Matsuoka, Yoshiki; Strauss, Michael A; Kashikawa, Nobunari; Onoue, Masafusa; Iwasawa, Kazushi; et al

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Abstract: We present new measurements of the quasar luminosity function (LF) at z similar to 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 deg(2) 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 similar to 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 alpha = -1.23(-0.34)(+0.44), a bright-end slope beta = -2.73(-0.31)(+0.23), a break magnitude M*(1450) = -24.90(-0.90)(+0.75), and a characteristic space density Phi* = 10.9(-6.8)(+10.0) 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 <(n)over dot>(ion) = 10(48.8 +/- 0.1) 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.
Publication Date: 20-Dec-2018
Citation: Matsuoka, Yoshiki, Strauss, Michael A, Kashikawa, Nobunari, Onoue, Masafusa, Iwasawa, Kazushi, Tang, Ji-Jia, Lee, Chien-Hsiu, Imanishi, Masatoshi, Nagao, Tohru, Akiyama, Masayuki, Asami, Naoko, Bosch, James, Furusawa, Hisanori, Goto, Tomotsugu, Gunn, James E, Harikane, Yuichi, Ikeda, Hiroyuki, Izumi, Takuma, Kawaguchi, Toshihiro, Kato, Nanako, Kikuta, Satoshi, Kohno, Kotaro, Komiyama, Yutaka, Lupton, Robert H, Minezaki, Takeo, Miyazaki, Satoshi, Murayama, Hitoshi, Niida, Mana, Nishizawa, Atsushi J, Noboriguchi, Akatoki, Oguri, Masamune, Ono, Yoshiaki, Ouchi, Masami, Price, Paul A, Sameshima, Hiroaki, Schulze, Andreas, Shirakata, Hikari, Silverman, John D, Sugiyama, Naoshi, Tait, Philip J, Takada, Masahiro, Takata, Tadafumi, Tanaka, Masayuki, Toba, Yoshiki, Utsumi, Yousuke, Wang, Shiang-Yu, Yamashita, Takuji. (2018). Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z=6. ASTROPHYSICAL JOURNAL, 869 (10.3847/1538-4357/aaee7a
DOI: doi:10.3847/1538-4357/aaee7a
ISSN: 0004-637X
EISSN: 1538-4357
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Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. This is an open access article.

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