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

Type Journal Article
Names M. Lacy, S. E. Ridgway, E. L. Gates, D. M. Nielsen, A. O. Petric, A. Sajina, T. Urrutia, S. Cox Drews, C. Harrison, N. Seymour, L. J. Storrie-Lombardi
Publication The Astrophysical Journal Supplement Series
Volume 208
Pages 24
Journal Abbreviation The Astrophysical Journal Supplement Series
Date October 1, 2013
DOI 10.1088/0067-0049/208/2/24
ISSN 0067-0049
Library Catalog
Abstract 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.
Tags galaxies: Seyfert, galaxies: starburst, infrared: galaxies, quasars: general
UW-Madison Astronomy Home