Issue |
A&A
Volume 479, Number 2, February IV 2008
|
|
---|---|---|
Page(s) | 389 - 396 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20078548 | |
Published online | 04 December 2007 |
The mid IR – hard X-ray correlation in AGN and its implications for dusty torus models *,**
1
Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15, 24098 Kiel, Germany e-mail: hhorst@astrophysik.uni-kiel.de
2
Zentrum für Astronomie, ITA, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
3
European Southern Observatory, Casilla 19001, Santiago 19, Chile
4
RIKEN Cosmic Radiation Lab, 2-1 Hirosawa, Wakoshi Saitama 351-0198, Japan
5
Steward Observatory, The University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721, USA
Received:
24
August
2007
Accepted:
15
November
2007
Aims.We investigate mid-infrared and X-ray properties of the dusty torus invoked in the unification scenario for active galactic nuclei by using the relation between mid IR and hard X-ray luminosities to constrain the geometry and physical state of the dusty torus.
Methods.We present new VISIR observations of 17 nearby AGN and combined these with our earlier VISIR sample of 8 Seyfert galaxies. After combining these observations with X-ray data from the literature, we studied the correlation between their mid IR and hard X-ray luminosities.
Results.A statistically highly significant correlation is found between the
rest frame m (
) and 2-10 keV
(
) luminosities. Furthermore, with a
probability of 97%, we find that Sy 1 and Sy 2 nuclei have the same
distribution of
over
.
Conclusions.The high resolution of our MIR imaging allows us to exclude
any significant non-torus contribution to the AGN mid IR continuum,
thereby implying that the similarity in the
/
ratio between Sy 1s and
Sy 2s is intrinsic to AGN. We argue that this is best explained by
clumpy torus models. The slope of the correlation is in good
agreement with the expectations from the unified scenario and
indicates little to no change in the torus geometry with luminosity.
In addition, we demonstrate that the high angular resolution is
crucial for AGN studies in the IR regime.
Key words: galaxies: active / infrared: galaxies / X-rays: galaxies
© ESO, 2008
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