The Extremely Luminous Quasar Survey in the Sloan Digital Sky Survey Footprint. II. The North Galactic Cap Sample
McGreer, Ian D.
Rees, Jon M.
AffiliationUniv Arizona, Steward Observ
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PublisherIOP PUBLISHING LTD
CitationJan-Torge Schindler et al 2018 ApJ 863 144
Rights© 2018. The American Astronomical Society. All rights reserved.
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AbstractWe present the North Galactic Cap sample of the Extremely Luminous Quasar Survey (ELQS-N), which targets quasars with M-1450 < -27 at 2.8 <= z < 5 in an area of similar to 7600 deg(2) of the Sloan Digital Sky Survey (SDSS) footprint with 90 degrees < R.A. < 270 degrees. Based on a near-infrared/infrared JKW2 color cut, the ELQS selection efficiently uses random forest methods to classify quasars and to estimate photometric redshifts; this scheme overcomes some of the difficulties of pure optical quasar selection at z approximate to 3. As a result, we retain a completeness of > 70% over z similar to 3.0-5.0 at m(i) less than or similar to 17.5, limited toward fainter magnitudes by the depth of the Two Micron All Sky Survey. The presented quasar catalog consists of a total of 270 objects, of which 39 are newly identified in this work with spectroscopy obtained at the Vatican Advanced Technology Telescope and the MMT 6.5 m telescope. In addition to the high completeness, which allowed us to discover new quasars in the already well-surveyed SDSS North Galactic Cap, the efficiency of our selection is relatively high at similar to 79%. Using 120 objects of this quasar sample we are able to extend the previously measured optical quasar luminosity function (QLF) by one magnitude toward the bright end at 2.8 <= z <= 4.5. A first analysis of the QLF suggests a relatively steep bright-end slope of beta approximate to -4 for this sample. This result contrasts with previous results in the same redshift range, which find a much flatter slope around beta similar to -2.5, but agrees with recent measurements of the bright-end slope at lower and higher redshifts. Our results constrain the bright-end slope at z = 2.8-4.5 to beta < -2.94 with a 99% confidence.
VersionFinal published version
SponsorsU.S. NSF [AST 15-15115]; NASA ADAP grant [NNX17AF28G]; National Aeronautics and Space Administration; National Science Foundation; Alfred P. Sloan Foundation; U.S. Department of Energy Office of Science; Center for High-Performance Computing at the University of Utah; Brazilian Participation Group; Carnegie Institution for Science; Carnegie Mellon University; Chilean Participation Group; French Participation Group; Harvard-Smithsonian Center for Astrophysics; Instituto de Astrofsica de Canarias; Johns Hopkins University; Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo; Lawrence Berkeley National Laboratory; Leibniz Institut fur Astrophysik Potsdam (AIP); Max-Planck-Institut fur Astronomie (MPIA Heidelberg); Max-Planck-Institut fur Astrophysik (MPA Garching); Max-Planck-Institut fur Extraterrestrische Physik (MPE); National Astronomical Observatories of China; New Mexico State University; New York University; University of Notre Dame; Observatrio Nacional/MCTI; Ohio State University; Pennsylvania State University; Shanghai Astronomical Observatory; United Kingdom Participation Group; Universidad Nacional Autnoma de Mexico; University of Arizona; University of Colorado Boulder; University of Oxford; University of Portsmouth; University of Utah; University of Virginia; University of Washington; University of Wisconsin; Vanderbilt University; Yale University