AGN Populations in Large-volume X-Ray Surveys: Photometric Redshifts and Population Types Found in the Stripe 82X Survey
Kirkpatrick, Allison; Nandra, Kirpal; Marchesi, Stefano; LaMassa, Stephanie; Natarajan, Priyamvada; Urry, C. Megan; Gilfanov, Marat; Farrah, Duncan; Lanzuisi, Giorgio; Merloni, Andrea; Cappelluti, Nico; Ananna, Tonima Tasnim; Salvato, Mara; Glikman, Eilat; Richards, Gordon T.; Civano, Francesca; Cardamone, Carolin; Hamilton, Mark; Timlin, John
United States, Germany, Russia, Italy
Abstract
Multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (AGNs). Stripe 82X is a 31.3 X-ray survey with Chandra and XMM-Newton observations overlapping the legacy Sloan Digital Sky Survey Stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. The wide-area nature of this survey presents new challenges for photometric redshifts for AGNs compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. Here we present an updated X-ray plus multiwavelength matched catalog, including Spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) X-ray sources that have a normalized median absolute deviation, σnmad=0.06, and an outlier fraction, η = 13.7%. The populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as eROSITA and 3XMM (in X-ray) and the Large Synoptic Survey Telescope (optical).