ITC Seminar - Ben Bar-Or (IAS)

 

Feeding central black holes with stars Abstract: Galactic nuclei and the Massive black holes in their centers are richenvironments, where the complex stellar dynamics plays an important role inmany physical phenomena. We show how the dynamics of this nearly-KeplerianN-body system, where the angular momentum evolution is accelerated by resonantrelaxation, can be described and studied in a formal statistical mechanicsframework. We combine the Fokker-Plank description of two-body relaxation andresonant relaxation to study the loss-cone dynamics in Galactic nuclei. We showthat low-mass black hole seeds that grow in a locally dense environment byaccreting stars in galactic nuclei that follow a universal M-sigma relation,all grow over the age of the universe above a present-day mass scale M ~10^5-10^6 Msun. This can explain why no Intermediate-mass black holes werefound to date, and implies that most present-day galaxies with sigma < 50 lacka central black hole. AGNs in low mass galaxies may provide evidence forcentral black holes which grow mainly by accrediting stars, and their velocitydispersion distribution can be used to test this model.