Publications of the MPIfR
Optical & Infrared
Interferometry Group
Beckert, T.; Duschl, W.J.
The dynamical state of a thick cloudy torus
around an AGN
Astronomy and Astrophysics, v.426, p.445-454 (2004)
Abstract
We present stationary models of obscuring dusty tori around active
galactic nuclei. Vertical and radial structure are discussed separately
based on a dynamical approach to a cloudy accretion flow. The vertical
cloud distribution is described by a modified isothermal disk for
arbitrary thickness of the torus with a wide funnel along the symmetry
axis. The radial accretion flow is a consequence of cloud-cloud
collisions. Accretion in the combined gravitational potential of
central
black hole and stellar cluster generates free energy, which is
dissipated in collisions, and maintains the thickness of the torus. We
focus on the largest clouds at the tidal shear limit, which will
dominate the dynamics and the appearance of torus. Successful
obscuration as required by unified schemes of AGN is achieved for large
mass accretion rates above the Eddington limit of the central black
hole. A complete quantitative treatment for the putative torus in the
prototypical Seyfert 2 nucleus of NGC 1068 is given.
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