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Title: First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey

In this paper, 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 deg 2 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 closemore » 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. Finally, 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.« less
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [3] ;  [1] ; ORCiD logo [4] ; ORCiD logo [5] ;  [6] ;  [3] ; ORCiD logo [5] ; ORCiD logo [7] ; ORCiD logo [8] ;  [9] ;  [5] ;  [10] ; ORCiD logo [3] ; ORCiD logo [11] ;  [12] ;  [9] ;  [13] more »; ORCiD logo [14] ;  [15] « less
  1. Peking Univ., Beijing (China); Univ. of Arizona, Tucson, AZ (United States)
  2. Univ. of Arizona, Tucson, AZ (United States); Peking Univ., Beijing (China)
  3. Peking Univ., Beijing (China)
  4. Australian National Univ., Canberra, ACT (Australia)
  5. Univ. of Arizona, Tucson, AZ (United States)
  6. Univ. of Michigan, Ann Arbor, MI (United States)
  7. National Optical Astronomy Observatory, Tucson, AZ (United States)
  8. Univ. of Nottingham (United Kingdom)
  9. Univ. of Wyoming, Laramie, WY (United States)
  10. Cerro Tololo Inter-American Observatory (CTIO), La Serena (Chile); Univ. of Washington, Seattle, WA (United States)
  11. Univ. of Toronto, ON (Canada)
  12. Univ. of Edinburgh, Scotland (United Kingdom). Royal Observatory
  13. Univ. of Edinburgh, Scotland (United Kingdom). Royal Observatory; Drexel Univ., Philadelphia, PA (United States)
  14. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  15. Durham Univ. (United Kingdom)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; AST 15-15115; 11373008; 11533001; 2014CB845700; 2016YFA0400703; XDB09000000
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 839; Journal Issue: 1; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
Peking Univ., Beijing (China); Univ. of Arizona, Tucson, AZ (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF); National Natural Science Foundation of China (NNSFC); National Key Basic Research Program of China; Ministry of Science and Technology of China; Strategic Priority Research Program (China); Science and Technology Facilities Council (STFC) (United Kingdom)
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; active galaxies; high-redshift galaxies; emission lines of quasars; quasars
OSTI Identifier: