Southern Cosmology Survey III: QSO's from Combined GALEX and Optical Photometry
Raul Jimenez, David N. Spergel, Michael D. Niemack, Felipe Menanteau,, John P. Hughes, Licia Verde, Arthur Kosowsky

TL;DR
This study demonstrates that deep GALEX ultraviolet photometry combined with optical data can effectively identify quasar candidates, offering an alternative method especially in regions lacking u-band optical data.
Contribution
First catalog of QSO candidates in the BCS region using GALEX and optical photometry, showing high efficiency comparable to multi-wavelength methods in low dust areas.
Findings
GALEX-based selection achieves ~95% completeness in low dust regions.
Approximately 40-60% of GALEX-selected QSOs match existing catalogs.
Deep GALEX data can substitute for u-band optical photometry in QSO identification.
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%)…
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