The formation and feeding of supermassive black holes in galactic centers

Wolfgang J. Duschl1, Peter A. Strittmatter2
1 Institut für Theoretische Astrophysik, Universität Heidelberg, Germany
2 Steward Observatory, The University of Arizona, Tucson, AZ, USA

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Normal galaxies like ours, and (mildly) active ones, like Seyfert galaxies, have typically smaller central black holes than quasars. We argue that this is mainly due to the merger history of the different types of (active) galaxies. We present model calculations which indicate that for the formation of the most massive black holes (10^9 M_sun or more) a major merger is required while less massive ones are formed through normal accretion in a galactic center. As a consequence of this, the formation of the most massive black holes is a very fast process which occurs preferentially in the young Universe, while for the evolution of a black hole as in the center of our galaxy, most of the Hubble time is needed. Finally, we will discuss the implications on the relation between the different types and levels of galactic activity.