Seminar: Depressions and instabilities: the dynamics of stars near massive black holes

Ann-Marie Madigan 

University of Leiden, The Netherlands

Artist's impression of a massive black hole. Credit: Credit: Aurore Simonnet/Sonoma State University/NASA.

Download the pdf poster.

The Galactic centre, at a distance of 8 kpc, 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 stellar disk (~ 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 both the eccentricity distribution of young stars, through an instability in an eccentric stellar disk, and the deficit of old stars, involving the mechanism of tidal disruption by the MBH.