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Title: 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

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 {sub bol} ∼ 10{sup 10} L {sub ☉} to highly luminous quasars (L {sub bol} ∼ 10{sup 14} L {sub ☉}), 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 A{sub V} ∼> 5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (A{sub V} ∼ 1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L {sub bol} > 10{sup 12} L {sub ☉}, in the quasar regime. We present composite spectra for type 2 quasars andmore » 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.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11]
  1. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
  2. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
  3. UCO/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States)
  4. Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States)
  5. Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
  6. Department of Physics and Astronomy, Tuffs University, 212 College Avenue, Medford, MA 02155 (United States)
  7. Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)
  8. 946 Mangrove Avenue 102, Sunnyvale, CA 94086 (United States)
  9. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
  10. CSIRO, P.O. Box 76, Epping, NSW 1710 (Australia)
  11. Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22273310
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 208; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTROSCOPY; ASTRONOMY; ASTROPHYSICS; BOLOMETERS; COLOR; CORRELATIONS; FLUX DENSITY; GALAXY NUCLEI; INFRARED SPECTRA; LUMINOSITY; QUASARS; RED SHIFT; SEYFERT GALAXIES; X RADIATION