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

Abstract

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.

Citation

Wang, F., Fan, X., Yang, J., Wu, X., Yang, Q., Bian, F., …Shanks, T. (2017). First discoveries of z > 6 quasars with the DECam Legacy Survey and UKIRT hemisphere survey. Astrophysical Journal, 839(1), 1-8. https://doi.org/10.3847/1538-4357/aa689f

• 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
• DOI: https://doi.org/10.3847/1538-4357/aa689f
• Keywords: galaxies: active, galaxies: high-redshift, quasars: emission lines, quasars: general
• Public URL: https://nottingham-repository.worktribe.com/output/855844
• Publisher URL: http://iopscience.iop.org/article/10.3847/1538-4357/aa689f/meta
• 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