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Title:
The Infrared Nuclear Emission of Seyfert Galaxies on Parsec Scales: Testing the Clumpy Torus Models
Authors:
Ramos Almeida, C.; Levenson, N. A.; Rodríguez Espinosa, J. M.; Alonso-Herrero, A.; Asensio Ramos, A.; Radomski, J. T.; Packham, C.; Fisher, R. S.; Telesco, C. M.
Affiliation:
AA( Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain ), AB( Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506, USA ), AC( Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain ), AD( Instituto de Estructura de la Materia, CSIC, E-28006 Madrid, Spain ), AE( Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain ), AF( Gemini South Observatory, Casilla 603, La Serena, Chile ), AG( Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611-2055, USA ), AH( Gemini Observatory, Northern Operations Center, 670 North Aòhoku Place, Hilo, HI 96720, USA), AI( Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611-2055, USA )
Publication:
The Astrophysical Journal, Volume 702, Issue 2, pp. 1127-1149 (2009). (ApJ Homepage)
Publication Date:
09/2009
Origin:
IOP
ApJ Keywords:
galaxies: active, galaxies: nuclei, galaxies: Seyfert, infrared: galaxies
DOI:
10.1088/0004-637X/702/2/1127
Bibliographic Code:
2009ApJ...702.1127R

Abstract

We present subarcsecond resolution mid-infrared (mid-IR) photometry in the wavelength range from 8 to 20 μm of 18 Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample. We construct spectral energy distributions (SEDs) that the active galactic nucleus (AGN) dominates, relatively uncontaminated by starlight, adding near-IR measurements from the literature at similar angular resolution. We find that the IR SEDs of intermediate-type Seyferts are flatter and present higher 10 to 18 μm ratios than those of Seyfert 2 galaxies. We fit the individual SEDs with clumpy dusty torus models using the in-house-developed BayesClumpy tool. We find that the clumpy models reproduce the high spatial resolution measurements. Regardless of the Seyfert type, even with high spatial resolution data, near- to mid-IR SED fitting poorly constrains the radial extent of the torus. For the Seyfert 2 galaxies, we find that edge-on geometries are more probable than face-on views, with a number of clouds along equatorial rays of N 0 = 5-15. The 10 μm silicate feature is generally modeled in shallow absorption. For the intermediate-type Seyferts, N 0 and the inclination angle of the torus are lower than those of the Seyfert 2 nuclei, with the silicate feature appearing in weak emission or absent. The columns of material responsible for the X-ray absorption are larger than those inferred from the model fits for most of the galaxies, which is consistent with X-ray absorbing gas being located within the dust sublimation radius, whereas the mid-IR flux arises from an area farther from the accretion disk. The fits yield both the bolometric luminosity of the intrinsic AGN and the torus-integrated luminosity, from which we derive the reprocessing efficiency of the torus. In the models, the outer radial extent of the torus scales with the AGN luminosity, and we find the tori to be confined to scales less than 5 pc.
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