Where have all the black holes gone?

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_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_Edd synchrotron emission and Bremsstrahlung dominate the SED, while above 2 10**-4 M 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.

7 pages, 5 figures, accepted for publication in A&A

References in corpus (2)

• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• The Nature of the 10 Kilosecond X-ray Flare in Sgr A*

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• Magnetospheric Gamma-Ray Emission in Active Galactic Nuclei
• The Cosmological History of Accretion onto Dark Halos and Supermassive Black Holes
• Capture of a Red Giant by the Black Hole Sagittarius A* as a Possible Origin for the TeV Gamma Rays from the Galactic Center
• Viscous time lags between starburst and AGN activity
• Searching for quantum-gravity footprint around stellar-mass black holes