Presentation Archive

The dynamics of stars near massive black holes

Ann-Marie Madigan

November 15, 2011

Abstract: The Galactic center is home to our nearest massive black hole (MBH). Recent observations of the stars orbiting in its potential have yielded unexpected results. In this talk I will discuss two such puzzles. The first is the presence of a young disk of stars (~ 6 Myr) which contains orbits with both very high and very low eccentricities. The second is a “hole” in the population of late-type stars (> 1 Gyr), in contradiction with the long-standing theoretical prediction of a stellar cusp increasing in density towards an MBH. I will present new results showing that secular (long-term) stellar dynamics can account for the eccentricity distribution of the young stars, through an instability in an eccentric stellar disk. The same dynamics can also, to some extent, explain the deficit of old stars, involving the mechanism of tidal disruption by the MBH. Finally, I will present a gravitational-dynamical process that occurs when an intermediate-mass black hole is migrating on an eccentric orbit through a nuclear star cluster towards a central MBH. This new mechanism is responsible for the increase in the intermediate-mass black hole’s orbital eccentricity as seen in N-body simulations.