On R − W1 as a diagnostic to discover obscured active galactic nuclei in wide-area X-ray surveys
- Yale Center for Astronomy and Astrophysics, Physics Department, P.O. Box 208120, New Haven, CT 06520 (United States)
- Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy)
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
- Department of Physics, Middlebury College, Middlebury, VT 05753 (United States)
- Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada)
- INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
- Department of Math and Science, Wheelock College, 200 Riverway, Boston, MA 02215 (United States)
- Department of Physics MC 0435, Virginia Polytechnic Institute and State University, 850 West Campus Drive, Blacksburg, VA 24061 (United States)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
- Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München (Germany)
- Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC (United States)
- Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)
- Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli Strasse 27, CH-8093 Zurich (Switzerland)
Capitalizing on the all-sky coverage of WISE and the 35% and 50% sky coverage from Sloan Digital Sky Survey and Pan-STARRS, respectively, we explore the efficacy of m{sub R} (optical) – m{sub 3.4μm} (mid-infrared), hereafter R−W1, as a color diagnostic to identify obscured supermassive black hole accretion in wide-area X-ray surveys. We use the ∼16.5 deg{sup 2} Stripe 82 X-ray survey data as a test bed to compare R−W1 with R − K, an oft-used obscured active galactic nucleus (AGN) selection criterion, and examine where different classes of objects lie in this parameter space. Most stars follow a well-defined path in R − K versus R−W1 space. We demonstrate that optically normal galaxies hosting X-ray AGNs at redshifts 0.5<1 can be recovered with an R−W1>4 color cut, while they typically are not selected as AGNs based on their W1−W2 colors. Additionally, different observed X-ray luminosity bins favor different regions in R−W1 parameter space: moderate-luminosity AGNs (10{sup 43} erg s{sup −1}10{sup 45} erg s{sup −1}) have bluer colors; higher spectroscopic completeness of the Stripe 82X sample is needed to determine whether this is a selection effect or an intrinsic property. Finally, we parameterize X-ray obscuration of Stripe 82X AGNs by calculating their hardness ratios (HRs) and find no clear trends between HR and optical reddening. Our results will help inform best-effort practices in following up obscured AGN candidates in current and future wide-area, shallow X-ray surveys, including the all-sky eROSITA mission.
- OSTI ID:
- 22887039
- Journal Information:
- Astrophysical Journal, Vol. 818, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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