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

Chehade, B.; Carnall, A.C.; Shanks, T.; Diener, C.; Fumagalli, M.; Findlay, J.R.; Metcalfe, N.; Hennawi, J.; Leibler, C.; Murphy, D.N.A.; Prochaska, J.X.; Irwin, M.J.; Gonzalez-Solares, E.

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 deg2 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 zAB = 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 M1450Å ≈ −27. Preliminary virial mass estimates based on the CIV and MgII emission lines give black hole masses in the range MBH ≈ 1 − 6 × 109M⊙ for the four ATLAS quasars.

Citation

Chehade, B., Carnall, A., Shanks, T., Diener, C., Fumagalli, M., Findlay, J., …Gonzalez-Solares, E. (2018). Two more, bright, z > 6 quasars from VST ATLAS and WISE. Monthly Notices of the Royal Astronomical Society, 478(2), 1649-1659. https://doi.org/10.1093/mnras/sty690

• Journal Article Type: Article
• Acceptance Date: Feb 23, 2018
• Online Publication Date: Mar 19, 2018
• Publication Date: Aug 1, 2018
• Deposit Date: Apr 5, 2018
• Publicly Available Date: Apr 6, 2018
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 478
• Issue: 2
• Pages: 1649-1659
• DOI: https://doi.org/10.1093/mnras/sty690