Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 380, Issue 3, Pages 1172-1176Publisher
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2007.12157.x
Keywords
galaxies : active; galaxies : nuclei; quasars : general; galaxies : Seyfert
Categories
Ask authors/readers for more resources
A cornerstone of active galactic nuclei (AGN) unification schemes is the presence of an optically and a geometrically thick dust torus. It provides the obscuration to explain the difference between type 1 and type 2 AGN. We investigate the influence of the dust distribution on the Eddington limit of the torus. For smooth dust distributions, the Eddingtion limit on the dust alone is five orders of magnitudes below the limit for electron scattering in a fully ionized plasma, while a clumpy dust torus has an Eddington limit slightly larger than the classical one. We study the behaviour of a clumpy torus at low and high AGN luminosities. For low luminosities of the order of similar to 10(42) erg s(-1), the torus changes its characteristics and obscuration becomes insufficient. In the high-luminosity regime, the clumpy torus can show a behaviour which is consistent with the 'receding torus' picture. The derived luminosity-dependent fraction of type 2 objects agrees with recent observational results. Moreover, the luminosity-dependent covering factor in a clumpy torus may explain the presence of broad-line AGN with high column densities in X-rays.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available