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

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, Simon Dye, Joseph R. Findlay, Richard Green, David James, Linhua Jiang, Dustin Lang, Andy Lawrence, Adam D. Myers, Nicholas P. RossDavid J. Schlegel, Tom Shanks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We present the first discoveries from a survey of z greater than or similar to 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) similar to 23.0, and UKIDSS and UHS will map the northern sky at 0 <decl. <+ 60 degrees, reaching J(VEGA) similar to 19.6 (5-sigma). The combination of these data sets allows us to discover quasars at redshift z greater than or similar to 7 and to conduct a complete census of the faint quasar population at z greater than or similar to 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z greater than or similar to 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z similar to 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 angstrom 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 greater than or similar to 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 greater than or similar to 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield similar to 200 z similar to 6 quasars to z(AB) <21.5, similar to 1000 z similar to 6 quasars to z(AB) <23, and similar to 30 quasars at z > 6.5 to J(VEGA) <19.5.

Original languageEnglish
Article number27
Number of pages8
JournalAstrophysical Journal
Volume839
Issue number1
DOIs
Publication statusPublished - 11 Apr 2017

Keywords

  • galaxies: active
  • galaxies: high-redshift
  • quasars: emission lines
  • quasars: general
  • DIGITAL SKY SURVEY
  • FIELD SPECTROGRAPH WIFES
  • INFRARED-SURVEY-EXPLORER
  • Z-GREATER-THAN-5.7 QUASARS
  • LUMINOSITY FUNCTION
  • ADDITIONAL QUASARS
  • REDSHIFT
  • PAN-STARRS1
  • Z-SIMILAR-TO-6
  • STRIPE

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