EFFICIENT PHOTOMETRIC SELECTION OF QUASARS FROM THE SLOAN DIGITAL SKY SURVEY. II. ∼1, 000, 000 QUASARS FROM DATA RELEASE 6

By Gordon Richards, Robert Nichol, Alexander G. Gray, Robert J. Brunner, Robert Lupton, D. V. vanden Berk, S. Chong, M. Weinstein, D. Schneider, S. Anderson and 8 more. Astrophysical Journal Supplement Series, 2004

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We present a catalog of 1,172,157 quasar candidates selected from the photometric imaging data of the Sloan Digital Sky Survey (SDSS). The objects are all point sources to a limiting magnitude of i = 21.3 from 8417 deg2 of imaging from SDSS Data Release 6 (DR6). This sample extends our previous catalog by using the latest SDSS public release data and probing both ultraviolet (UV)-excess and high-redshift quasars. While the addition of high-redshift candidates reduces the overall efficiency (quasars:quasar candidates) of the catalog to ∼80%, it is expected to contain no fewer than 850,000 bona fide quasars, which is ∼8 times the number of our previous sample and ∼10 times the size of the largest spectroscopic quasar catalog. Cross-matching between our photometric catalog and spectroscopic quasar catalogs from both the SDSS and 2dF survey yields 88,879 spectroscopically confirmed quasars. For judicious selection of the most robust UV-excess sources (∼500, 000 objects in all), the efficiency is nearly 97%—more than sufficient for detailed statistical analyses. The catalog's completeness to type 1 (broad-line) quasars is expected to be no worse than 70%, with most missing objects occurring at z < 0.7 and 2.5 < z < 3.0. In addition to classification information, we provide photometric redshift estimates (typically good to Δz ± 0.3 [2σ]) and cross-matching with radio, X-ray, and proper-motion catalogs. Finally, we consider the catalog's utility for determining the optical luminosity function of quasars and are able to confirm the flattening of the bright-end slope of the quasar luminosity function at z ∼ 4 as compared to z ∼ 2.

Subfields: Astronomy and Astrophysics, Ecology

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Citations in the corpus

Measuring the galaxy–mass and galaxy–dust correlations through magnification and reddening (2009, methodology): “The quasar data set was generated using the kernel den- sity estimation (KDE) method described in Richards et al. (2004) applied to the DR3 data set.”
Quasars Probing Quasars. I. Optically Thick Absorbers near Luminous Quasars (2006, positive): “Richards et al. (2004) constructed a photometric catalog of z < 3 quasars from the SDSS imaging data that has high completeness and efficiency and photometric redshifts accurate to zj jP 0:3.”
Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales (2005, methodology): “…with the UV-excess region of color space (u g < 0:6) but outside the region populated bywhite dwarfs (Richards et al. 2002b), (2) match amember of the faint photometric catalog of Richards et al. (2004) (extended to the DR3 region), or (3) are optically unresolved and match a FIRST radio source.”
THE PRISM MULTI-OBJECT SURVEY (PRIMUS). I. SURVEY OVERVIEW AND CHARACTERISTICS (2010, methodology): “In the two DEEP2 fields, we targeted photometrically-selected AGN with g < 21 and g−i < 2 from Richards et al. (2004).”
Average extinction curves and relative abundances for quasi-stellar object absorption-line systems at 1 ≤zabs < 2 (2006, background): “…images in the SDSS filter system (Fukugita et al. 1996), QSOs can be reliably separated from most types of stars, and reasonably accurate photometric redshifts can be estimated for a large fraction of the quasar candidates, using only colour data (Richards et al. 2004; Weinstein et al. 2004).”
Probing the Interstellar Medium near Star-forming Regions with Gamma-Ray Burst Afterglow Spectroscopy: Gas, Metals, and Dust (2007, methodology): “To estimate the effects, we assessed the signal-to-noise ratio (S/N) at the center of the Lyα profile of each QSO-DLAs in the SDSSDR3 sample.”
First Measurement of the Clustering Evolution of Photometrically Classified Quasars (2005, methodology): “For example, Richards et al. (2004) have developed a Bayesian method to separate quasars from stars in the four-dimensional color-space of the SDSS, with nominal stellar contamination as low as 5% for redshifts of 0:2P zP 2:4.”
CLUSTERING OF LOW-REDSHIFT (z ⩽ 2.2) QUASARS FROM THE SLOAN DIGITAL SKY SURVEY (2008, methodology): “Myers et al. (2006) reported a measurement of the clustering of quasars using ∼ 80 000 SDSS quasars photometrically classified from the catalogue of Richards et al. (2004).”
The Sloan Digital Sky Survey Quasar Survey: Quasar Luminosity Function from Data Release 3 (2006, methodology): “We can define appreciably larger samples yet, using the photometric selection and photometric redshift techniques of Richards et al. (2004a) and Weinstein et al. (2004); such methods will result in a sample approaching a million quasars probing appreciably further down the luminosity function,…”