TORUS AND ACTIVE GALACTIC NUCLEUS PROPERTIES OF NEARBY SEYFERT GALAXIES: RESULTS FROM FITTING INFRARED SPECTRAL ENERGY DISTRIBUTIONS AND SPECTROSCOPY

Journal Article · Mon Aug 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/2/82· OSTI ID:21578282

Alonso-Herrero, Almudena ^[1]; Ramos Almeida, Cristina ^[2]; Mason, Rachel ^[3]; Asensio Ramos, Andres; Rodriguez Espinosa, Jose Miguel; Perez-Garcia, Ana M ^[4]; Roche, Patrick F ^[5]; Levenson, Nancy A ^[6]; Elitzur, Moshe ^[7]; Packham, Christopher ^[8]; Young, Stuart ^[9]; Diaz-Santos, Tanio ^[10]

---

1. Departamento de Astrofisica, Centro de AstrobiologIa, INTA-CSIC, Carretera de Torrejon a Ajalvir km 4, Torrejon de Ardoz, E-28850 Madrid (Spain)
2. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)
3. Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
4. Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)
5. Astrophysics, Department of Physics, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom)
6. Gemini Observatory, Casilla 603, La Serena (Chile)
7. Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States)
8. Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611-2055 (United States)
9. Department of Physics, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States)
10. Department of Physics, University of Crete, GR-71003 Heraklion (Greece)

We used the CLUMPY torus models and a Bayesian approach to fit the infrared spectral energy distributions and ground-based high angular resolution mid-infrared spectroscopy of 13 nearby Seyfert galaxies. This allowed us to put tight constraints on torus model parameters such as the viewing angle i, the radial thickness of the torus Y, the angular size of the cloud distribution {sigma}{sub torus}, and the average number of clouds along radial equatorial rays N{sub 0}. We found that the viewing angle i is not the only parameter controlling the classification of a galaxy into type 1 or type 2. In principle, type 2s could be viewed at any viewing angle i as long as there is one cloud along the line of sight. A more relevant quantity for clumpy media is the probability for an active galactic nucleus (AGN) photon to escape unabsorbed. In our sample, type 1s have relatively high escape probabilities, P{sub esc} {approx} 12%-44%, while type 2s, as expected, tend to have very low escape probabilities. Our fits also confirmed that the tori of Seyfert galaxies are compact with torus model radii in the range 1-6 pc. The scaling of the models to the data also provided the AGN bolometric luminosities L{sub bol}(AGN), which were found to be in good agreement with estimates from the literature. When we combined our sample of Seyfert galaxies with a sample of PG quasars from the literature to span a range of L{sub bol}(AGN) {approx} 10{sup 43}-10{sup 47} erg s{sup -1}, we found plausible evidence of the receding torus. That is, there is a tendency for the torus geometrical covering factor to be lower (f{sub 2} {approx} 0.1-0.3) at high AGN luminosities than at low AGN luminosities (f{sub 2} {approx} 0.9-1 at {approx}10{sup 43}-10{sup 44} erg s{sup -1}). This is because at low AGN luminosities the tori appear to have wider angular sizes (larger {sigma}{sub torus}) and more clouds along radial equatorial rays. We cannot, however, rule out the possibility that this is due to contamination by extended dust structures not associated with the dusty torus at low AGN luminosities, since most of these in our sample are hosted in highly inclined galaxies.

• OSTI ID: 21578282
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 736; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION SPECTROSCOPY
ENERGY SPECTRA
GALAXIES
GALAXY NUCLEI
INFRARED SPECTRA
SEYFERT GALAXIES
SPECTRA
SPECTROSCOPY
TORI