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

被引:183
作者
Alonso-Herrero, Almudena [1 ,2 ]
Almeida, Cristina Ramos [3 ]
Mason, Rachel [4 ]
Asensio Ramos, Andres [5 ,6 ]
Roche, Patrick F. [7 ]
Levenson, Nancy A. [8 ]
Elitzur, Moshe [9 ]
Packham, Christopher [10 ]
Rodriguez Espinosa, Jose Miguel [5 ,6 ]
Young, Stuart [11 ]
Diaz-Santos, Tanio [12 ]
Perez-Garcia, Ana M. [5 ,6 ]
机构
[1] INTA CSIC, Ctr Astrobiol, Dept Astrofis, E-28850 Madrid, Spain
[2] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[3] Univ Sheffield, Dept Phys & Astron, Sheffield S3 7RH, S Yorkshire, England
[4] No Operat Ctr, Gemini Observ, Hilo, HI 96720 USA
[5] Inst Astrofis Canarias, E-38205 Tenerife, Spain
[6] Univ La Laguna, Dept Astrofis, E-38205 Tenerife, Spain
[7] Univ Oxford, Dept Phys, DWB, Oxford OX1 3RH, England
[8] Gemini Observ, La Serena, Chile
[9] Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA
[10] Univ Florida, Bryant Space Sci Ctr 211, Dept Astron, Gainesville, FL 32611 USA
[11] Rochester Inst Technol, Dept Phys, Rochester, NY 14623 USA
[12] Univ Crete, Dept Phys, GR-71003 Iraklion, Greece
基金
美国国家科学基金会; 美国国家航空航天局;
关键词
galaxies: nuclei; galaxies: Seyfert; galaxies: structure; infrared: galaxies; NARROW-LINE REGION; RESOLVED MIDINFRARED SPECTROSCOPY; MU-M; CIRCINUS GALAXY; NGC; 1068; SPATIAL-RESOLUTION; DUSTY TORUS; SILICATE FEATURES; OBSCURING TORUS; UNIFIED SCHEMES;
D O I
10.1088/0004-637X/736/2/82
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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(torus), and the average number of clouds along radial equatorial rays N-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-esc similar to 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-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-bol(AGN) similar to 10(43)-10(47) erg s(-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(2) similar to 0.1-0.3) at high AGN luminosities than at low AGN luminosities (f(2) similar to 0.9-1 at similar to 10(43)-10(44) erg s(-1)). This is because at low AGN luminosities the tori appear to have wider angular sizes (larger sigma(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.
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页数:30
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