Filling in the quasar redshift gap at z ∼ 5.5. II. A complete survey of luminous quasars in the post-reionization universe

Jinyi Yang, Feige Wang, Xiaohui Fan, Xue Bing Wu, Fuyan Bian, Eduardo Banãdos, Minghao Yue, Jan Torge Schindler, Qian Yang, Linhua Jiang, Ian D. McGreer, Richard Green, Simon Dye

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We present the final results from our survey of luminous z ∼ 5.5 quasars. This is the first systematic quasar survey focusing on quasars at z ∼ 5.5, during the post-reionization epoch. It has been challenging to select quasars at 5.3 < z < 5.7 using conventional color selections, due to their similar optical colors to those of late-type stars, especially M dwarfs. We developed a new selection technique for z ∼ 5.5 quasars based on optical, near-infrared (IR), and mid-IR photometry, using data from the Sloan Digital Sky Survey (SDSS), PanSTARR1 (PS1), the UKIRT Infrared Deep Sky Surveys-Large Area Survey, the UKIRT Hemisphere Survey, the VISTA Hemisphere Survey, and the Wide Field Infrared Survey Explorer, covering ∼11,000 deg 2 of high galactic latitude sky. In this paper, we present the discovery of 15 new quasars at 5.22 ≤ z ≤ 5.78. Together with results from Yang et al., our survey provides a complete, flux-limited sample of 31 quasars at 5.3 ≤ z ≤ 5.7. We measure the quasar spatial density at z ∼ 5.5 and M 1450 <-26.2. Our result is consistent with the rapid decline of the quasar spatial density from z = 5 to 6, with k =-0.66 ± 0.05 (ρ(z) ∝ 10 kz ). In addition, we present a new survey using optical colors only from the full PS1 area for luminous quasars at z = 5.0-5.5, which is beyond the SDSS footprint, and report the preliminary results from this survey, including 51 new quasars discovered at 4.61 ≤ z ≤ 5.71.

Original languageEnglish (US)
Article number199
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 1 2019


  • galaxies: Active
  • galaxies: High-redshift
  • quasars: Emission lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Filling in the quasar redshift gap at z ∼ 5.5. II. A complete survey of luminous quasars in the post-reionization universe'. Together they form a unique fingerprint.

Cite this