AGN populations in large-volume X-ray surveys: Photometric redshifts and population types found in the stripe 82X survey

Tonima Tasnim Ananna, Mara Salvato, Stephanie Lamassa, C. Megan Urry, Nico Cappelluti, Carolin Cardamone, Francesca Civano, Duncan Farrah, Marat Gilfanov, Eilat Glikman, Mark Hamilton, Allison Kirkpatrick, Giorgio Lanzuisi, Stefano Marchesi, Andrea Merloni, Kirpal Nandra, Priyamvada Natarajan, Gordon T. Richards, John Timlin

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


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).

Original languageEnglish (US)
Article number66
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 20 2017
Externally publishedYes


  • Catalogs
  • Quasars: absorption lines
  • Quasars: emission lines
  • Quasars: general
  • Techniques: photometric
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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