IDENTIFYING LUMINOUS ACTIVE GALACTIC NUCLEI IN DEEP SURVEYS: REVISED IRAC SELECTION CRITERIA

Journal Article · Sun Apr 01 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/748/2/142· OSTI ID:22016060

Donley, J L; Koekemoer, A M ^[1]; Brusa, M; Salvato, M ^[2]; Capak, P ^[3]; Cardamone, C N ^[4]; Civano, F ^[5]; Ilbert, O ^[6]; Impey, C D ^[7]; Kartaltepe, J S ^[8]; Miyaji, T ^[9]; Sanders, D B ^[10]; Trump, J R ^[11]; Zamorani, G ^[12]

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1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2. Max Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei Muenchen (Germany)
3. Spitzer Science Center, California Institute of Technology, MC 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
4. Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
5. Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
6. Laboratoire d'Astrophysique de Marseille (UMR 6110), CNRS-Universite de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13 (France)
7. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
8. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
9. Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California (Mexico)
10. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
11. UCO/Lick, University of California, Santa Cruz, CA 95064 (United States)
12. INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

Spitzer/IRAC selection is a powerful tool for identifying luminous active galactic nuclei (AGNs). For deep IRAC data, however, the AGN selection wedges currently in use are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGNs and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high-redshift star-forming galaxies selected via the BzK, distant red galaxy, Lyman-break galaxy, and submillimeter galaxy criteria. At QSO luminosities of log L{sub 2-10keV}(erg s{sup -1}) {>=}44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 52% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log N{sub H} (cm{sup -2}) = 23.5 {+-} 0.4). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGNs, it is incomplete to low-luminosity and host-dominated AGNs.

• OSTI ID: 22016060
• Journal Information: Astrophysical Journal, Vol. 748, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
GALACTIC EVOLUTION
GALAXY NUCLEI
HARD X RADIATION
LUMINOSITY
RED SHIFT
STAR EVOLUTION
STARS
UNIVERSE
X-RAY GALAXIES