The dense stellar systems around galactic massive black holes

Abstract

The central regions of galaxies show the presence of massive black holes and/or dense stellar systems. The question about their modes of formation is still under debate. A likely explanation of the formation of the central dense stellar systems in both spiral and elliptical galaxies is based on the orbital decay of massive globular clusters in the central region of galaxies due to kinetic energy dissipation by dynamical friction. Their merging leads to the formation of a nuclear star cluster, like that of the Milky Way, where a massive black hole (Sgr A * ) is also present. Actually, high precision N-body simulations (Antonini, Capuzzo-Dolcetta et al. 2012, [1]) show a good fit to the observational characteristics of the Milky Way nuclear cluster, giving further reliability to the cited migratory model for the formation of compact systems in the inner galaxy regions.

A performance comparison of different graphics processing units running direct N-body simulations

“…Specifically, using our very small, green and cheap cluster composed by two computational nodes each composed by two multicore CPUs and 4 HD 7970 GPUs, we may evolve the system K3 for 10 9 years in around 75 days of simulation, reaching a peak of 10 Tflops of sustained performance. For the sake of future applications of actual astrophysical interest we are dealing with the formation and the long term (Gyr) Such systems are often observed in the central regions of galaxies; in particular, more steps forward are to be done in the numerical simulations of the so called Milky Way Nuclear Star Cluster, whose model of formation and evolution are still under debate (see [28] and [29]). Through preliminary tests, we estimated that we can evolve this system, modelled using N = 2M stars plus a central massive black hole, up to 1 Myr in around 8 hours.…”