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

Abstract

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.

Star Formation and ISM Properties in the Host Galaxies of Three Far-infrared Luminous Quasars at z ∼ 6

“…More than 200 quasars have been discovered above redshift 5.7 (e.g., Fan et al 2006;Mortlock et al 2009Mortlock et al , 2011Willott et al 2009Willott et al , 2010aVenemans et al 2013Venemans et al , 2015Bañados et al 2014Bañados et al , 2016Bañados et al , 2018Jiang et al 2015Jiang et al , 2016Matsuoka et al 2016Matsuoka et al , 2018Mazzucchelli et al 2017). These high redshift quasars are key to understand the co-evolution between supermassive black holes (SMBHs) and their host galaxies at the end of the reionization epoch.…”

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

“…Quasars are powered by supermassive black holes (SMBHs) with ≈ 10 8−10 M⊙ (e.g., De Rosa et al 2014;Wu et al 2015). Owing to wide-area surveys, ≈ 100 quasars are discovered at z > 6 (e.g., Fan et al 2003;Jiang et al 2016;Mazzucchelli et al 2017;Matsuoka et al 2018) and up to z = 7.54 (Bañados et al 2018). How SMBHs have accreted within ≈ 1 Gyr after the Big Bang is one of the most important question in modern astronomy (Valiante et al 2017).…”

Truth or Delusion? A Possible Gravitational Lensing Interpretation of the Ultraluminous Quasar SDSS J010013.02+280225.8 at z = 6.30

“…In the last two decades, more than 100 z ∼ 6 QSOs have been discovered through wide-field surveys in the optical-near infrared (NIR) wavelengths (e.g., Jiang et al 2009Jiang et al , 2016Willott et al 2010;Venemans et al 2013Venemans et al , 2015Bañados et al 2016;Matsuoka et al 2016Matsuoka et al , 2018. Currently, the most massive BH at z > 6 ever known is J0100+2802 at z = 6.30 (Wu et al 2015), originally identified owing to its red optical color with the dataset of the Sloan Digital Sky Survey (SDSS; York et al 2000), two Micron All Sky Survey (2MASS; Skrutskie et al 2006) and the Wide-field Infrared Survey Explorer (WISE; Wright et al 2010).…”