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
Year: 2019
Type: article
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 in the magnitude range −27.6 < M 1450 < −25.5. We determine the quasar comoving spatial density at = 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.
Source: The Astrophysical Journal
Authors: 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 Venemans, Fabian Walter, Simon Dye, Brad W. Lyke, Adam D. Myers, Evan Haze Nunez
Institutions: University of Arizona, University of California, Santa Barbara, Peking University, University of Michigan, European Southern Observatory, Carnegie Institution for Science, Carnegie Observatories, University of Wyoming, Osservatorio di Astrofisica e Scienza dello Spazio, National Institute for Astrophysics, Max Planck Institute for Astronomy, University of Nottingham, El Camino College, California State Polytechnic University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, California Institute of Technology, Chinese Academy of Sciences, Ministério da Ciência e Tecnologia, Jet Propulsion Laboratory, University of California, Los Angeles, Science and Technology Facilities Council, Comisión Nacional de Investigación Científica y Tecnológica, National Astronomical Observatories, Chinese Academy of Sciences
OpenAlex ID: W2898371591