SUBARU HIGH-z EXPLORATION of LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY of 15 QUASARS and BRIGHT GALAXIES at 5.7 < z < 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 KikutaYutaka 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

Research output: Contribution to journalArticle

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Abstract

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.

Original languageEnglish (US)
Article number26
JournalAstrophysical Journal
Volume828
Issue number1
DOIs
StatePublished - Sep 1 2016

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • dark ages, reionization, first stars
  • galaxies: active
  • galaxies: high-redshift
  • intergalactic medium
  • quasars: general
  • quasars: supermassive black holes

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    Matsuoka, Y., Onoue, M., Kashikawa, N., Iwasawa, K., Strauss, M. A., Nagao, T., Imanishi, M., Niida, M., Toba, Y., Akiyama, M., Asami, N., Bosch, J., Foucaud, S., Furusawa, H., Goto, T., Gunn, J. E., Harikane, Y., Ikeda, H., Kawaguchi, T., ... Utsumi, Y. (2016). SUBARU HIGH-z EXPLORATION of LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY of 15 QUASARS and BRIGHT GALAXIES at 5.7 < z < 6.9. Astrophysical Journal, 828(1), [26]. https://doi.org/10.3847/0004-637X/828/1/26