THE FINAL SDSS HIGH-REDSHIFT QUASAR SAMPLE OF 52 QUASARS AT z > 5.7
McGreer, Ian D.
Strauss, Michael A.
Becker, Robert H.
White, Richard L.
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationTHE FINAL SDSS HIGH-REDSHIFT QUASAR SAMPLE OF 52 QUASARS AT z > 5.7 2016, 833 (2):222 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2016. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe present the discovery of nine quasars at z similar to 6 identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of z similar to 6 quasars in the SDSS footprint. Our final sample consists of 52 quasars at 5.7 < z << 6.4, including 29 quasars with z(AB) <= 20 mag selected from 11,240 deg(2) of the SDSS single-epoch imaging survey (the main survey), 10 quasars with 20 <= z(AB) <= 20.5 selected from 4223 deg2 of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to z(AB) approximate to 22 mag from the 277 deg2 in Stripe 82. They span a wide luminosity range of -29.0 <= M-1450 <= -24.5. This well-defined sample is used to derive the quasar luminosity function (QLF) at z similar to 6. After combining our SDSS sample with two faint (M-1450 >= -23 mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope beta of the QLF is well constrained to be beta = -2.8 +/- 0.2. Due to the small number of low-luminosity quasars, the faint-end slope a and the characteristic magnitude M*(1450) are less well constrained, with alpha = -1.90(-0.44)(+0.58) and M* = -25.2(-3.8)(+1.2) mag. The spatial density of luminous quasars, parametrized as rho(M-1450 < -26, z) = rho(z = 6)10(k(z-6)), drops rapidly from z similar to 5 to 6, with k = -0.72 +/- 0.11. Based on our fitted QLF and assuming an intergalactic medium (IGM) clumping factor of C = 3, we find that the observed quasar population cannot provide enough photons to ionize the z similar to 6 IGM at similar to 90% confidence. Quasars may still provide a significant fraction of the required photons, although much larger samples of faint quasars are needed for more stringent constraints on the quasar contribution to reionization.
VersionFinal published version
SponsorsMinistry of Science and Technology of China [2016YFA0400703]; National Science Foundation of China ; Thousand Youth Talents Program of China; NSF [AST 11-07682, 15-15115]; Alfred P. Sloan Research Fellowship; National Astronomical Observatories of China (NAOC); Chinese Academy of Sciences (the Strategic Priority Research Program "The Emergence of Cosmological Structures") [XDB09000000]; Special Fund for Astronomy from the Ministry of Finance; Alfred P. Sloan Foundation; National Science Foundation; U.S. Department of Energy; National Aeronautics and Space Administration; Japanese Monbukagakusho; Max Planck Society; Higher Education Funding Council for England