Discovery of 16 Newz∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection

Jinyi Yang, Xiaohui Fan, Xue-Bing Wu, Feige Wang, Fuyan Bian, Qian Yang, Ian D. McGreer, Weimin Yi, Linhua Jiang, Richard Green, Minghao Yue, Shu Wang (+4 others)
2017 Astronomical Journal  
We present initial results from the first systematic survey of luminous z∼ 5.5 quasars. Quasars at z ∼ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 < z < 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift
more » ... glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ∼ 5.5 quasars based on optical, near-IR and mid-IR photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys - Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS) and Wide field Infrared Survey Explorer (WISE). From our pilot observations in SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 < z < 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ∼ 5.5 quasars already published in our previous work, we now construct an uniform quasar sample at 5.3 < z < 5.7 with 17 quasars in a ∼ 4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ∼ 5.5 quasar.
doi:10.3847/1538-3881/aa6577 fatcat:uurbpayaavcllbhmj3264wnhxm