------------------------------------------------------------------------
From: "Wolfgang J. Duschl"  wjd@ita.uni-heidelberg.de 
To: hfalcke@mpifr-bonn.mpg.de
Cc: wjd@ita.uni-heidelberg.de
Subject: GC News
User-Agent: Internet Messaging Program (IMP) 3.0
X-Originating-IP: 128.196.210.171


\title{Where have all the black holes gone?}
\author{T. Beckert (1), W. J. Duschl (2,1)}
\inst{(1) Max-Planck-Institut fuer Radioastronomie, Auf dem
Huegel 69, 53121 Bonn, Germany; (2) Institut fuer Theoretische Astro-
physik, Universitaet Heidelberg, Tiergartenstr. 15, 69121 Heidelberg,
Germany}
\begin{abstract}
  We have calculated stationary models for accretion disks
around super-massive black holes in galactic nuclei. Our models
show that below a critical mass flow rate of ~ 3 10**-3 M(dot)_Edd
advection will dominate the energy budget while above that rate all
the viscously liberated energy is radiated. The radiation efficiency
declines steeply below that critical rate. This leads to a clear
dichotomy between AGN and normal galaxies which is not so much given
by differences in the mass flow rate but by the radiation efficiency.
At very low mass accretion rates below 5 10**-5 M(dot)_Edd synchrotron
emission and Bremsstrahlung dominate the SED, while above 2 10**-4
M(dot)_Edd the inverse Compton radiation from synchrotron seed photons
produce flat to inverted SEDs from the radio to X-rays. Finally we
discuss the implications of these findings for AGN duty cycles and the
long-term AGN evolution.
\end{abstract}