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Astron. Astrophys. 341, 675-682 (1999)


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AGN polarization models

S. Wolf 1 and Th. Henning 2

1 Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany
2 Astrophysikalisches Institut und Universitäts-Sternwarte (AIU), Schillergässchen 3, D-07745 Jena, Germany

Received 31 July 1998 / Accepted 4 November 1998

Abstract

We present model calculations for the scattered flux and polarization of nuclear radiation having in mind the AGN unification scheme. It is our aim to survey the influence of several model parameters, especially, the influence of the torus. Additionally, we considerably improved present models, for instance by including multiple instead of single scattering.

For these purposes, we developed a Monte-Carlo radiative transfer code for both electron and dust scattering (Thomson and Rayleigh/Mie scattering). Irradiation from a point-like source can be treated as well as extended anisotropic radiation sources and dust re-emission.

We found that the observed wavelength dependence of the linear polarization of some AGNi can be explained by dust scattering in optically thin cones, whereby the additional presence of electrons increases the absolute amount of polarization. The torus geometry and density profile as well as the thermal dust re-emission also influence the polarization degree. Multiple scattering in the cones was found to be important for optical depths above [FORMULA] 0.1.

Key words: galaxies: Seyfert – galaxies: active – radiative transfer – scattering – polarization

Send offprint requests to: S. Wolf (wolf@tls-tautenburg.de)

© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998

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