We identify 885,503 type 1 quasar candidates to i ≲ 22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) "AllWISE" data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with 3.5 < z > 5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z > 3.5 than the traditional mid-IR selection "wedges" and to 2.2 <z < 3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z > 3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.
- infrared: galaxies
- methods: statistical
- quasars: general
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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Richards, G. T. (Creator), Myers, A. D. (Creator), Peters, C. M. (Creator), Krawczyk, C. M. (Creator), Chase, G. (Creator), Ross, N. P. (Creator), Fan, X. (Creator), Jiang, L. (Creator), Lacy, M. (Creator), McGreer, I. D. (Creator), Trump, J. R. (Creator) & Riegel, R. N. (Creator), Centre de Donnees Strasbourg (CDS), 2015