%0 Generic %1 carnall2015bright %A Carnall, A. C. %A Shanks, T. %A Chehade, B. %A Fumagalli, M. %A Rauch, M. %A Irwin, M. J. %A Gonzalez-Solares, E. %A Findlay, J. R. %A Metcalfe, N. %D 2015 %K atlas quasars selection %T Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infra-red colour selection %U http://arxiv.org/abs/1502.07748 %X We present the discovery of two z > 6 quasars, selected as i band dropouts in the VST ATLAS survey. Our first quasar has redshift, z = 6.31 0.03, z band magnitude, zAB = 19.63 0.08 and rest frame 1450A absolute magnitude, M1450 = -27.8 0.2, making it one of the two most luminous quasars known at z > 6. The second quasar has z = 6.02 0.03, zAB = 19.54 0.08 and M1450 = -27.0 0.1. We also recover a z = 5.86 quasar discovered by Venemans et al. (2015, in prep.). To select our quasars we use a new 3D colour space, combining the ATLAS optical colours with mid-infra-red data from the WISE Space Telescope. We use iAB - zAB colour to exclude main sequence stars, galaxies and lower redshift quasars, W1 - W2 to exclude L dwarfs and zAB - W2 to exclude T dwarfs. A restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of \sim50%. We discuss how less restrictive cuts in our 3D colour space can be used to reject the majority of contaminants from samples of bright 5.7 < z < 6.4 quasars, replacing follow-up near-infra-red photometry, whilst retaining high completeness.

@misc{carnall2015bright, abstract = {We present the discovery of two z > 6 quasars, selected as i band dropouts in the VST ATLAS survey. Our first quasar has redshift, z = 6.31 \pm 0.03, z band magnitude, zAB = 19.63 \pm 0.08 and rest frame 1450A absolute magnitude, M1450 = -27.8 \pm 0.2, making it one of the two most luminous quasars known at z > 6. The second quasar has z = 6.02 \pm 0.03, zAB = 19.54 \pm 0.08 and M1450 = -27.0 \pm 0.1. We also recover a z = 5.86 quasar discovered by Venemans et al. (2015, in prep.). To select our quasars we use a new 3D colour space, combining the ATLAS optical colours with mid-infra-red data from the WISE Space Telescope. We use iAB - zAB colour to exclude main sequence stars, galaxies and lower redshift quasars, W1 - W2 to exclude L dwarfs and zAB - W2 to exclude T dwarfs. A restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of \sim50%. We discuss how less restrictive cuts in our 3D colour space can be used to reject the majority of contaminants from samples of bright 5.7 < z < 6.4 quasars, replacing follow-up near-infra-red photometry, whilst retaining high completeness.}, added-at = {2015-03-02T09:55:55.000+0100}, author = {Carnall, A. C. and Shanks, T. and Chehade, B. and Fumagalli, M. and Rauch, M. and Irwin, M. J. and Gonzalez-Solares, E. and Findlay, J. R. and Metcalfe, N.}, biburl = {https://www.bibsonomy.org/bibtex/22bfbfa12f9a3d94c75a9568dae8a3270/miki}, description = {[1502.07748] Two bright z &gt; 6 quasars from VST ATLAS and a new method of optical plus mid-infra-red colour selection}, interhash = {0e8a3f4a3077576111f5cb6733318733}, intrahash = {2bfbfa12f9a3d94c75a9568dae8a3270}, keywords = {atlas quasars selection}, note = {cite arxiv:1502.07748Comment: 5 pages, 2 figures, submitted to MNRAS letters}, timestamp = {2015-03-02T09:55:55.000+0100}, title = {Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infra-red colour selection}, url = {http://arxiv.org/abs/1502.07748}, year = 2015 }