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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.

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


B. Chehade

A.C. Carnall

T. Shanks

C. Diener

J.R. Findlay

J. Hennawi

C. Leibler

D.N.A. Murphy

J.X. Prochaska

M.J. Irwin

E. Gonzalez-Solares


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.


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.

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


Accepted Journal Article (1.1 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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