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

• Published in: The Astrophysical journal 2017-04, Vol.839 (1), p.27
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: active galaxies; ASTRONOMY AND ASTROPHYSICS; Astrophysics; Datasets; emission lines of quasars; galaxies: active; galaxies: high-redshift; high-redshift galaxies; Luminosity; Near infrared radiation; Northern sky; Quasars; quasars: emission lines; quasars: general; Red shift; Sky surveys (astronomy)
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aa689f

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 zAB ∼ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching JVEGA ∼ 19.6 (5- ). 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 being M1450 = −25.83 and M1450 = −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 M1450 = −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 zAB < 21.5, ∼1000 z ∼ 6 quasars to zAB < 23, and ∼30 quasars at z > 6.5 to JVEGA < 19.5.