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First discoveries of z > 6 quasars with the DECam Legacy Survey and UKIRT hemisphere survey

Wang, Feige; Fan, Xiaohui; Yang, Jinyi; Wu, Xue-Bing; Yang, Qian; Bian, Fuyan; McGreer, Ian D.; Li, Jiang-Tao; Li, Zefeng; Ding, Jiani; Dey, Arjun; Dye, Simon; Findlay, Joseph R.; Green, Richard; James, David; Jiang, Linhua; Lang, Dustin; Lawrence, Andy; Myers, Adam D.; Ross, Nicholas P.; Schlegel, David J.; Shanks, Tom

First discoveries of z > 6 quasars with the DECam Legacy Survey and UKIRT hemisphere survey Thumbnail


Feige Wang

Xiaohui Fan

Jinyi Yang

Xue-Bing Wu

Qian Yang

Fuyan Bian

Ian D. McGreer

Jiang-Tao Li

Zefeng Li

Jiani Ding

Arjun Dey

Associate Professor

Joseph R. Findlay

Richard Green

David James

Linhua Jiang

Dustin Lang

Andy Lawrence

Adam D. Myers

Nicholas P. Ross

David J. Schlegel

Tom Shanks


We present the first discoveries from a survey of z 6 quasars using imaging data from the DECam Legacy Survey (DECaLS) in the optical, the UKIRT Deep Infrared Sky Survey (UKIDSS) and a preliminary version of the UKIRT Hemisphere Survey (UHS) in the near-IR, and ALLWISE in the mid-IR. DECaLS will image 9000 deg2 of sky down to z AB ~ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching J VEGA ~ 19.6 (5-σ). The combination of these data sets allows us to discover quasars at redshift z 7 and to conduct a complete census of the faint quasar population at z 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z ~ 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 Å being M 1450 = −25.83 and M 1450 = −25.76, respectively. These discoveries suggest that we can find quasars close to or fainter than the break magnitude of the Quasar Luminosity Function (QLF) at z 6. The new z = 6.63 quasar has an absolute magnitude of M 1450 = −25.95. This demonstrates the potential of using the combined DECaLS and UKIDSS/UHS data sets to find z 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield ~200 z ~ 6 quasars to z AB < 21.5, ~1000 z ~ 6 quasars to z AB < 23, and ~30 quasars at z > 6.5 to J VEGA < 19.5.

Journal Article Type Article
Acceptance Date Apr 10, 2017
Online Publication Date Apr 11, 2017
Publication Date Apr 11, 2017
Deposit Date Apr 27, 2017
Publicly Available Date Apr 27, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 839
Issue 1
Article Number 27
Pages 1-8
Keywords galaxies: active, galaxies: high-redshift, quasars: emission lines, quasars: general
Public URL
Publisher URL
Additional Information Journal title: The Astrophysical Journal; Article type: paper; Article title: First Discoveries ofz> 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey; Copyright information: © 2017. The American Astronomical Society. All rights reserved.; Date received: 2016-10-23; Date accepted: 2017-03-20; Online publication date: 2017-04-11


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