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Description
This table contains a catalog of over 130,000 quasar candidates with near-infrared (NIR) photometric properties, with an areal coverage of approximately 1200 deg<sup>2</sup>. This is achieved by matching the Sloan Digital Sky Survey (SDSS) in the optical ugriz bands to the UKIRT Infrared Digital Sky Survey (UKIDSS) Large Area Survey (LAS) in the NIR YJHK bands. The authors match the ~1 million SDSS DR6 Photometric Quasar catalog to Data Release 3 of the UKIDSS LAS (ULAS) and produce a catalog with 130,827 objects with detections in one or more NIR bands, of which 74,351 objects have optical and K-band detections and 42,133 objects have the full nine-band photometry. The majority (~85%) of the SDSS objects were not matched simply because these were not covered by the ULAS. The positional standard deviation of the SDSS Quasar to ULAS matches is 0.1370 arcseconds in RA and 0.1314 arcseconds in Dec. The authors find an absolute systematic astrometric offset between the SDSS Quasar catalog and the UKIDSS LAS, of |RA offset| = 0.025 arcseconds and |Dec offset| = 0.040 arcseconds; they suggest the nature of this offset to be due to the matching of catalog, rather than image, level data. Their matched catalog has a surface density of ~53 deg<sup>-2</sup> for K <= 18.27 objects; tests using this matched catalog, along with data from the UKIDSS Deep Extragalactic Survey, imply that its limiting magnitude is i ~ 20.6. Color-redshift diagrams, for the optical and NIR, show a close agreement between this matched catalog and recent quasar color models at redshift z <~ 2.0, while at higher redshifts, the models generally appear to be bluer than the mean observed quasar colors. This table was created by the HEASARC in September 2012 based on CDS Catalog J/AJ/141/105 file table4.dat. This is a service provided by NASA HEASARC .
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