Insights on the dusty torus and neutral torus from optical and X-ray obscuration in a complete volume limited hard X-ray AGN sample

Journal Article · Wed Jun 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/806/1/127· OSTI ID:22883056

Davies, R. I.; Burtscher, L.; Rosario, D.; Contursi, A.; Genzel, R.; Carpio, J. Graciá-; Janssen, A.; Lin, M. -Y.; Lutz, D.; Xivry, G. Orban de; Müller, A. Schnorr- ^[1]; Storchi-Bergmann, T.; Riffel, R. ^[2]; Hicks, E. ^[3]; Koss, M. ^[4]; Maciejewski, W. ^[5]; Sánchez, F. Müller- ^[6]; Ricci, C. ^[7]; Riffel, R. A. ^[8]; Schartmann, M. ^[9] ; others, and

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1. Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, D-85741, Garching (Germany)
2. Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS (Brazil)
3. Astronomy Department, University of Alaska, Anchorage (United States)
4. Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)
5. Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146 Brownlow Hill, L3 5RF (United Kingdom)
6. Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States)
7. Pontificia Universidad Católica de Chile, Instituto de Astrofísica, Casilla 306, Santiago 22 (Chile)
8. Departamento de Física, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil)
9. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, 3122 (Australia)

We describe a complete volume limited sample of nearby active galaxies selected by their 14–195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We also describe a complementary sample of inactive galaxies, selected to match the host galaxy properties. The active sample appears to have no bias in terms of active galactic nucleus (AGN) type, the only difference being the neutral absorbing column, which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, logL{sub 14−195 keV}[erg s{sup −1}]=42.4–43.7, the optically obscured and X-ray absorbed fractions are 50%–65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad-line region (BLR) emission, and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus.

• OSTI ID: 22883056
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 806; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
COSMIC DUST
COSMIC GASES
EMISSION
GALAXY NUCLEI
HARD X RADIATION
KEV RANGE
LUMINOSITY
RED SHIFT
SEYFERT GALAXIES
X-RAY GALAXIES