Bayesian High-redshift Quasar Classification from Optical and Mid-IR Photometry
Abstract
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\lt z\lt 5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z\gt 3.5 than the traditional mid-IR selection “wedges” and to 2.2\lt z\lt 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\gt 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.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- August 2015
- DOI:
- 10.1088/0067-0049/219/2/39
- arXiv:
- arXiv:1507.07788
- Bibcode:
- 2015ApJS..219...39R
- Keywords:
-
- catalogs;
- infrared: galaxies;
- methods: statistical;
- quasars: general;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 54 pages, 17 figures