Exploring Reionization-era Quasars. IV. Discovery of Six New z ⪆ 6.5 Quasars with DES, VHS, and unWISE Photometry

Jinyi Yang, Feige Wang, Xiaohui Fan, Minghao Yue, Xue Bing Wu, Jiang Tao Li, Fuyan Bian, Linhua Jiang, Eduardo Bañados, Yuri Beletsky

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


This is the fourth paper in a series of publications aiming at discovering quasars at the epoch of reionization. In this paper, we expand our search for z ∼ 7 quasars to the footprint of the Dark Energy Survey (DES) Data Release One (DR1), covering ∼5000 deg2 of a new area. We select z ∼ 7 quasar candidates using deep optical, near-infrared (near-IR) and mid-infrared (mid-IR) photometric data from the DES DR1, the VISTA Hemisphere Survey, the VISTA Kilo-degree Infrared Galaxy survey, the UKIRT InfraRed Deep Sky Surveys - Large Area Survey (ULAS), and the unblurred coadds from the Wide-field Infrared Survey Explore (WISE) images (unWISE). The inclusion of DES and unWISE photometry allows the search to reach ∼1 mag fainter, comparing to our z ⪆ 6.5 quasar survey in the northern sky. We report the initial discovery and spectroscopic confirmation of six new luminous quasars at z > 6.4, including an object at z = 7.02, the fourth quasar yet known at z > 7, from a small fraction of candidates observed thus far. Based on the recent measurement of z ∼ 6.7 quasar luminosity function using the quasar sample from our survey in the northern sky, we estimate that there will be ⪆55 quasars at z > 6.5 at M 1450 < -24.5 in the full DES footprint.

Original languageEnglish (US)
Article number236
JournalAstronomical Journal
Issue number6
StatePublished - 2019


  • galaxies: active
  • galaxies: high-redshift
  • quasars: emission lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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