Multi-wavelength 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 ( AGN ) .
Stripe 82X is a 31.3 deg ^ { 2 } X-ray survey with Chandra and XMM -Newton observations overlapping the legacy Sloan Digital Sky Survey ( SDSS ) Stripe 82 field , which has a rich investment of multi-wavelength coverage from the ultraviolet to the radio .
The wide-area nature of this survey presents new challenges for photometric redshifts for AGN 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 multi-wavelength matched catalog , including Spitzer counterparts , and estimated photometric redshifts for 5961 ( 96 % of a total of 6181 ) X-ray sources , which have a normalized median absolute deviation , \sigma _ { nmad } = 0.06 and an outlier fraction , \eta = 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 3 XMM ( in X-ray ) and the Large Synoptic Survey Telescope ( LSST ; optical ) .