Southern Cosmology Survey III: QSO's from Combined GALEX and Optical Photometry

Abstract

We present catalogs of QSO candidates selected using photometry from GALEX combined with SDSS in the Stripe 82 region and Blanco Cosmology Survey (BCS) near declination -55 degrees. The SDSS region contains ~700 objects with magnitude i < 20 and ~3600 objects with i < 21.5 in a ~60 square degree sky region, while the BCS region contains ~280 objects with magnitude i < 20 and ~2000 objects with i < 21.5 for a 11 square degree sky region that is being observed by three current microwave Sunyaev-Zeldovich surveys. Our QSO catalog is the first one in the BCS region. Deep GALEX exposures (~2000 seconds in FUV and NUV, except in three fields) provide high signal-to-noise photometry in the GALEX bands (FUV, NUV < 24.5 mag). From this data, we select QSO candidates using only GALEX and optical r-band photometry, using the method given by Atlee and Gould (2008). In the Stripe 82 field, 60% (30%) of the GALEX selected QSO's with optical magnitude i<20 (i<21.5) also appear in the Richards et al. (2008) QSO catalog constructed using 5-band optical SDSS photometry. Comparison with the same catalog by Richards et al. shows that the completeness of the sample is approximately 40%(25%). However, for regions of the sky with very low dust extinction, like the BCS 23hr field and the Stripe 82 between 0 and 10 degrees in RA, our completeness is close to 95%, demonstrating that deep GALEX observations are almost as efficient as multi-wavelength observations at finding QSO's. GALEX observations thus provide a viable alternate route to QSO catalogs in sky regions where u-band optical photometry is not available. The full catalog is available at http://www.ice.csic.es/personal/jimenez/PHOTOZ

Submitted to ApJS

References in corpus (6)

• Statistical Properties of the GALEX/SDSS matched source catalogs, and classification of the UV sources
• Measuring AGN Feedback with the Sunyaev-Zel'dovich Effect
• Simulations of the Sunyaev-Zeldovich Effect from Quasars
• The Sunyaev-Zeldovich Effect from Quasar Feedback
• Photometric Selection of QSO Candidates From GALEX Sources
• Improving Photometric Redshifts using GALEX Observations for the SDSS Stripe 82 and the Next Generation of SZ Cluster Surveys

Cited by in corpus (3)

• The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics and Data Release
• Think Outside the Color Box: Probabilistic Target Selection and the SDSS-XDQSO Quasar Targeting Catalog
• Photometric redshifts and quasar probabilities from a single, data-driven generative model