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Title: Luminosity and redshift dependence of the covering factor of active galactic nuclei viewed with WISE and Sloan digital sky survey

In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 μm luminosity functions (LFs) at 0.006 ≤z ≤ 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 μm and 25,721 galaxies at 22 μm for spectroscopic classification. We then identified 16,355 AGNs at 12 μm and 4683 AGNs at 22 μm by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z ≤ 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can bemore » explained by the receding torus model, but the 'modified' receding torus model gives a slightly better fit, as suggested by Simpson.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ; ; ; ; ; ;  [5] ;  [6] ;  [7]
  1. Department of Space and Astronautical Science, the Graduate University for Advanced Studies (Sokendai), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
  2. Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)
  3. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States)
  4. Department of Physics, Durham University, Durham DH1-3LE (United Kingdom)
  5. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
  6. Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617 Taiwan (China)
  7. Misato Observatory, 180 Matsugamine, Misato-cho, Kaiso-gun, Wakayama 640-1366 (Japan)
Publication Date:
OSTI Identifier:
22356687
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CLASSIFICATION; COLOR; EMISSION; GALAXIES; GALAXY NUCLEI; INFRARED SURVEYS; LUMINOSITY; MASS; RED SHIFT; SKY