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The Spitzer Mid-infrared Active Galactic Nucleus Survey. I. Optical and Near-infrared Spectroscopy of Obscured Candidates and Normal Active Galactic Nuclei Selected in the Mid-infrared
Lacy, M. ( National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA ); Ridgway, S. E. ( National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA ); Gates, E. L. ( UCO/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140, USA ); Nielsen, D. M. ( Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706, USA ); Petric, A. O. ( Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA ); Sajina, A. ( Department of Physics and Astronomy, Tuffs University, 212 College Avenue, Medford, MA 02155, USA ); Urrutia, T. ( Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany ); Cox Drews, S. ( 946 Mangrove Avenue #102, Sunnyvale, CA 94086, USA ); Harrison, C. ( Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA ); Seymour, N. ( CSIRO, P.O. Box 76, Epping, NSW 1710, Australia ); Storrie-Lombardi, L. J. ( Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA ) and 1 coauthors show affiliations
The Astrophysical Journal Supplement, Volume 208, Issue 2, article id. 24, 18 pp. (2013).
Published in Oct 2013
We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate active galactic nuclei (AGNs) selected in the mid-infrared. This survey selects both normal and obscured AGNs closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L bol ~ 1010 L to highly luminous quasars (L bol ~ 1014 L ), all with redshifts ranging from 0 to 4.3. Samples of candidate AGNs were selected with mid-infrared color cuts at several different 24 μm flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGNs and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type 1 AGNs with blue continua, 294 (44%) are type 2 objects with extinctions AV 〉~ 5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (AV ~ 1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L bol 〉 1012 L , in the quasar regime. We present composite spectra for type 2 quasars and objects with no signs of AGN activity in their spectra. We also discuss the mid-infrared—emission-line luminosity correlation and present the results of cross correlations with serendipitous X-ray and radio sources. The results show that: (1) obscured objects dominate the overall AGN population, (2) mid-infrared selected AGN candidates exist which lack AGN signatures in their optical spectra but have AGN-like X-ray or radio counterparts, and (3) X-ray and optical classifications of obscured and unobscured AGNs often differ.
Astronomy: galaxies: Seyfert; galaxies: starburst; infrared: galaxies; quasars: general
arXiv: Astrophysics - Cosmology and Nongalactic Astrophysics