Exploring Reionization-era Quasars. III. Discovery of 16 Quasars at 6.4 ≲ z ≲ 6.9 with DESI Legacy Imaging Surveys and the UKIRT Hemisphere Survey and Quasar Luminosity Function at z ∼ 6.7

Feige Wang, Jinyi Yang, Xiaohui Fan, Xue Bing Wu, Minghao Yue, Jiang Tao Li, Fuyan Bian, Linhua Jiang, Eduardo Bañados, Jan Torge Schindler, Joseph R. Findlay, Frederick B. Davies, Roberto Decarli, Emanuele P. Farina, Richard Green, Joseph F. Hennawi, Yun Hsin Huang, Chiara Mazzuccheli, Ian D. Mcgreer, Bram VenemansFabian Walter, Simon Dye, Brad W. Lyke, Adam D. Myers, Evan Haze Nunez

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

This is the third paper in a series aimed at finding reionization-era quasars with the combination of DESI Legacy imaging Surveys (DELS), the Pan-STARRS1 (PS1) Survey, and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey Explorer (WISE) mid-infrared survey. In this paper, we describe the updated quasar candidate selection procedure, report the discovery of 16 quasars at 6.4 ≲ z ≲ 6.9 from an area of ∼13,020 deg2, and present the quasar luminosity function (QLF) at z ∼ 6.7. The measured QLF follows Φ(L1450)∝ L1450 -2.35 in the magnitude range-27.6 < M 1450 <-25.5. We determine the quasar comoving spatial density at &langle; z&rangle; = 6.7 and M 1450 <-26.0 to be 0.39 ± 0.11 Gpc-3 and find the exponential density evolution parameter to be k =-0.78 ± 0.18 from z ∼ 6 to z ∼ 6.7, corresponding to a rapid decline by a factor of ∼6 per unit redshift toward earlier epochs. This indicates that the rapid decline of quasar spatial density at z > 5 that was found by previous works continues to z > 6, at a rate significantly faster than the average decline rate between z ∼ 3 and 5. We measured quasar comoving emissivity at z ∼ 6.7, which indicates that high-redshift quasars are highly unlikely to make a significant contribution to hydrogen reionization. The broad absorption line quasar fraction at z ⪆ 6.5 is measured to be ⪆22%. In addition, we also report the discovery of six additional quasars at z ∼ 6 in the Appendix.

Original languageEnglish (US)
Article number30
JournalAstrophysical Journal
Volume884
Issue number1
DOIs
StatePublished - Oct 10 2019

Keywords

  • early universe
  • galaxies: Active
  • galaxies: High-redshift
  • quasars: General

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'Exploring Reionization-era Quasars. III. Discovery of 16 Quasars at 6.4 ≲ z ≲ 6.9 with DESI Legacy Imaging Surveys and the UKIRT Hemisphere Survey and Quasar Luminosity Function at z ∼ 6.7'. Together they form a unique fingerprint.

  • Cite this

    Wang, F., Yang, J., Fan, X., Wu, X. B., Yue, M., Li, J. T., Bian, F., Jiang, L., Ba&ntilde;ados, E., Schindler, J. T., Findlay, J. R., Davies, F. B., Decarli, R., Farina, E. P., Green, R., Hennawi, J. F., Huang, Y. H., Mazzuccheli, C., Mcgreer, I. D., ... Nunez, E. H. (2019). Exploring Reionization-era Quasars. III. Discovery of 16 Quasars at 6.4 ≲ z ≲ 6.9 with DESI Legacy Imaging Surveys and the UKIRT Hemisphere Survey and Quasar Luminosity Function at z ∼ 6.7. Astrophysical Journal, 884(1), [30]. https://doi.org/10.3847/1538-4357/ab2be5