Two more, bright, z > 6 quasars from VST ATLAS and WISE

Abstract

Recently, Carnall et al. discovered two bright high redshift quasars using the combination of the VST ATLAS and WISE surveys. The technique involved using the 3-D colour plane i − z : z − W1 : W1 − W2 with the WISE W1(3.4 micron) and W2 (4.5 micron) bands taking the place of the usual NIR J band to help decrease stellar dwarf contamination. Here we report on our continued search for 5.7 < z < 6.4 quasars over an ≈ 2× larger area of ≈ 3577 deg 2 of the Southern Hemisphere. We have found two further z > 6 quasars, VST-ATLAS J158.6938-14.4211 at z = 6.07 and J332.8017-32.1036 at z = 6.32 with magnitudes of z AB = 19.4 and 19.7 mag respectively. J158.6938-14.4211 was confirmed by Keck LRIS observations and J332.8017-32.1036 was confirmed by ESO NTT EFOSC-2 observations. Here we present VLT X-shooter Visible and NIR spectra for the four ATLAS quasars. We have further independently rediscovered two z > 5.7 quasars previously found by the VIKING/KiDS and PanSTARRS surveys. This means that in ATLAS we have now discovered a total of six quasars in our target 5.7 < z < 6.4 redshift range. Making approximate corrections for incompleteness, we find that our quasar space density agrees with the SDSS results of Jiang et al. at M 1450Å ≈ −27. Preliminary virial mass estimates based on the CIV and MgII emission lines give black hole masses in the range M BH ≈ 1 − 6 × 10 9 M for the four ATLAS quasars.

Spectral Energy Distributions of Companion Galaxies to z ∼ 6 Quasars

“…This quasar was also recently independently discovered byChehade et al (2018), with the name of VST-ATLAS J332.8017−32.1036.…”

The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

“…For these sources we used the magnitudes at 1450 Å provided by Bañados et al (2016). We also include ULASJ1342+0928, which was discovered after (Bañados et al 2016;Mazzucchelli et al 2017;Reed et al 2017;Tang et al 2017;Wang et al 2017Wang et al , 2018aChehade et al 2018;Matsuoka et al 2018b,a;Yang et al 2019). Cyan symbols are QSOs with archival X-ray data (see Tab.…”

A new bright z = 6.82 quasar discovered with VISTA: VHS J0411–0907

“…It covers, over four years, the whole sky up to declination > −30 deg, i.e. more than 30,000 deg 2 , in five imaging filters (g P1 , r P1 , i P1 , z P1 , y P1 ; Chambers et al 2016 In all this paper the Pan-STARRS magnitudes cited referred to the PSF magnitudes (psfmag).…”

“…Currently ∼100 z > 6.0 quasars have been found mainly thanks to large-area optical and IR surveys such as the Sloan Digital Sky Survey (Fan et al 2001(Fan et al , 2003(Fan et al , 2004(Fan et al , 2006Jiang et al 2008Jiang et al , 2009Jiang et al , 2015Jiang et al , 2016Wang et al 2016), the Canada-France-Hawaii Telescope High-z Quasars Surveys (CFHQS; Willott et al 2007Willott et al , 2009Willott et al , 2010, the UK Infrared Deep Sky Survey (UKIDSS, including the two highest redshift quasars known; Mortlock et al 2009;Bañados et al 2018), the Pan-STARRS1 distant quasars survey (Bañados et al 2014(Bañados et al , 2016Venemans et al 2015;Tang et al 2017;Mazzucchelli et al 2017), the VST ATLAS survey (Carnall et al 2015;Chehade et al 2018) and the the Subaru High-z Exploration of Low-Luminosity Quasars survey (SHELLQS; Matsuoka et al 2016). In addition, deep surveys such as the Dark Energy Survey (Reed et al 2015, 2019), the DECam Legacy Survey (DECaLS; Wang et al 2017) and the VISTA Kilo-Degree Infrared Galaxy (VIKING) Survey (Venemans et al 2013) have been successful in the search of high-redshift quasars, in particular at redshift z > ∼ 6.5.…”