First discoveries ofz ∼ 6 quasars with the Kilo-Degree Survey and VISTA Kilo-Degree Infrared Galaxy survey

Abstract

We present the results of our first year of quasar search in the ongoing ESO public Kilo Degree Survey (KiDS) and VISTA Kilo-Degree Infrared Galaxy (VIKING) surveys. These surveys are among the deeper wide-field surveys that can be used to uncover large numbers of z ∼ 6 quasars. This allows us to probe a more common population of z ∼ 6 quasars that is fainter than the well-studied quasars from the main Sloan Digital Sky Survey. From this first set of combined survey catalogues covering ∼250 deg 2 we selected point sources down to Z AB = 22 that had a very red i − Z (i − Z > 2.2) colour. After follow-up imaging and spectroscopy, we discovered four new quasars in the redshift range 5.8 < z < 6.0. The absolute magnitudes at a rest-frame wavelength of 1450Å are between −26.6 < M 1450 < −24.4, confirming that we can find quasars fainter than M * , which at z = 6 has been estimated to be between M * = −25.1 and M * = −27.6. The discovery of four quasars in 250 deg 2 of survey data is consistent with predictions based on the z ∼ 6 quasar luminosity function. We discuss various ways to push the candidate selection to fainter magnitudes and we expect to find about 30 new quasars down to an absolute magnitude of M 1450 = −24. Studying this homogeneously selected faint quasar population will be important to gain insight into the onset of the co-evolution of the black holes and their stellar hosts.

The first and second data releases of the Kilo-Degree Survey

“…The 9-band u through K s photometry from the combined surveys goes up to ∼2 mag deeper than SDSS, UKIDSS and the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1; Bañados et al 2014). So far we have discovered nine such QSOs, where the first four are published in Venemans et al (2015). KiDS is also a useful ingredient in the detection of very high redshift (z > 6.4) QSOs with VIKING.…”

SUBARU HIGH-z EXPLORATION OF LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY OF 15 QUASARS AND BRIGHT GALAXIES AT 5.7 < z < 6.9∗ †

“…With the advent of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-degree Infrared Galaxy (VIKING) survey, more z>6.5 quasars have been discovered in recent years (Venemans et al 2013(Venemans et al , 2015. New optical wide-field surveys such as the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1; Kaiser et al 2010) 3π survey and the Dark Energy Survey (Dark Energy Survey Collaboration et al 2016) are equipped with a y-band filter centered at 9500-10000 Å, and are starting to deliver many more quasars at 6z7 (Bañados et al 2014;Reed et al 2015).…”

Mapping the Lyα Emission around a z ∼ 6.6 QSO with MUSE: Extended Emission and a Companion at a Close Separation

“…Currently, there are more than 170 known QSOs at z>5.6 (e.g., Fan et al 2006;Jiang et al 2009;Willott et al 2010;Bañados et al 2014Bañados et al , 2015aBañados et al , 2016Carnall et al 2015;Reed et al 2015;Venemans et al 2015a;Jiang et al 2016;Matsuoka et al 2016), only 12 of which are located at z>6.5 (Mortlock et al 2011;Venemans et al 2013Venemans et al , 2015bMatsuoka et al 2016Matsuoka et al , 2017Mazzucchelli et al 2017a). The host galaxies of these very first QSOs are actively forming stars, with prodigious star-formation rates SFR>100 M yr 1 -  (Venemans et al 2012, and were able to grow SMBHs with masses exceeding M BH =10 9 M  in less than 800 Myr (De Rosa et al 2014;Venemans et al 2015b).…”