Issue |
A&A
Volume 404, Number 1, June II 2003
|
|
---|---|---|
Page(s) | 1 - 19 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20030427 | |
Published online | 26 May 2003 |
New radiative transfer models for obscuring tori in active galaxies
1
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
2
Max-Planck Institut für Astronomie, PO Box 1317, 85741 Garching, Germany
Corresponding author: I. M. van Bemmel, bemmel@stsci.edu
Received:
10
June
2002
Accepted:
17
March
2003
Two-dimensional radiative transfer is employed to obtain the
broad-band infrared spectrum of active galaxies. In the models we
vary the geometry and size of the obscuring medium, the surface
density, the opacity and the grain size distribution. Resulting
spectral energy distributions are constructed for different
orientations of the toroid. Colour-colour comparisons with
observational data are consistent with previous observations that
the emission longward of 60 m is produced by star-formation and
unrelated to the presence of an obscuring torus.
We also find that the toroid cannot be flat, but is rather conical
or flaring. The density is most likely constant with radius, and
the size is relatively large with an inner radius around 10 pc.
A direct comparison with radio galaxy Cygnus A yields a best fit for
a conical disk with constant surface density, and a size from 10
to 30 pc, assuming the far-infrared emission is due to star-formation
in the host galaxy.
Key words: galaxies: active / galaxies individual: Cygnus A / infrared: galaxies / infrared: ISM / quasars: general / ISM: dust
© ESO, 2003
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