Talks, Seminars, Events

Abstract
M31 is the nearest large galaxy for which we have a dust-free multi-wavelength picture of its central regions. It presents some puzzles. The inner few parsecs are dominated by a double nucleus, which is most naturally explained by Tremaine's (1995) model of an eccentric disc of old stars around a supermassive black hole. A more recent surprise is the discovery of a very compact cluster of young stars around the black hole. I review ongoing work on the construction of a coherent picture of this system and compare it to the clusters found at the centres of other nearby galaxies.

Abstract
Many if not most galaxies contain supermassive black holes. In a gas free situation they are embedded in a very dense stellar cluster. The black hole grows through tidal disruption of stars and accretion of other black holes (stellar mass or other supermassive black holes after galaxy mergers). We study these processes with large direct N-body simulations including relativistic Post-Newtonian dynamics when needed. We find that tidal disruption rates can be enhanced in axisymmetric galactic nuclei; this effect is even more pronounced during a phase after galaxy mergers when the gravitational potential is non-axisymmetric and strongly varying in time. Recent results show that also the presence of a gaseous disk in the central galactic regions will strongly enhance tidal disruption rates by trapping stars on nearly circular orbits confined within the disk. A stellar disk forms and after the removal of the gaseous disk the nucleus has some common features with our own Galactic Center. Inspired by recent detections we will also discuss in some detail the expected gravitational wave radiation from black hole mergers on all mass scales in galactic nuclei and star clusters.

Abstract
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