Globular cluster-massive black hole interactions in galactic centers

Many, if not all, galaxies host massive compact objects at their centers. They are present as singularities (super massive black holes) or high density star clusters (nuclear tar clusters). In some cases they coexist, and interact more or less strongly. In this short paper I will talk of the 'merger' globular cluster scenario, which has been shown in the past to be an explanation of the substantial mass accumulation in galactic centers. In particular, I will present the many astrophysical implications of such scenario pointing the attention on the mutual feedback of orbitally decaying globular clusters with massive and super massive black holes.Comment: 4 pages, 1 fiugre. Presented at the MODEST 16/Cosmic Lab conference in Bologna, Italy, April 18-22 2016. To be pusblshed in Mem. S.A.It. Conference Serie

Galactic nuclear activity induced by globular cluster merging

The interpretation of the difference observed between the radial distribution of globular clusters and that of halo-bulge stars in elliptical galaxies is discussed in terms of evolution of their globular cluster systems. I present a short summary of the evidence that dynamical evolution of globular cluster systems is not only able to explain the flattening of their distribution toward the galactic center, but also it may have played an important role on the primordial activity of the parent galaxy.Comment: Presented at the MPIA Workshop on Modes of Star Formation and the Origin of Field Populations, in press in the ASP Conf. Ser., Grebel and Brandner eds.; 7 pages including 2 eps figures and 1 tabl

An efficient parallel tree-code for the simulation of self-gravitating systems

We describe a parallel version of our tree-code for the simulation of self-gravitating systems in Astrophysics. It is based on a dynamic and adaptive method for the domain decomposition, which exploits the hierarchical data arrangement used by the tree-code. It shows low computational costs for the parallelization overhead -- less than 4% of the total CPU-time in the tests done -- because the domain decomposition is performed 'on the fly' during the tree setting and the portion of the tree that is local to each processor 'enriches' itself of remote data only when they are actually needed. The performances of an implementation of the parallel code on a Cray T3E are presented and discussed. They exhibit a very good behaviour of the speedup (=15 with 16 processors and 10^5 particles) and a rather low load unbalancing (< 10% using up to 16 processors), achieving a high computation speed in the forces evaluation (>10^4 particles/sec with 8 processors).Comment: 10 pages, 8 figures, LaTeX2e, A&A class file needed (included), submitted to A&A; corrected abstract word wrappin

Globular cluster system erosion and nucleus formation in elliptical galaxies

The radial distribution of globular clusters in galaxies is always less peaked to the centre than the halo stars'. Extending previous work to a sample of HST globular cluster systems in ellipticals, we evaluate the number of clusters lost to the galactic centre as the integrals of the difference between the observed globular cluster system distribution and the underlying halo light profile. It results that the initial populations of globular clusters were from 25% to 50% richer than now. This significant number of missing globular clusters supports the hypothesis that a large quantity of globular cluster mass in form of globular clusters decayed and destroyed has been lost to the galactic centres, where plausibly contributed to formation and feeding of a mas sive object therein. It is relevant noting that the observed correlation between the core radius of the globular cluster system and the parent galaxy luminosity can be interpreted as a result of evolution.Comment: Latex file + 2 figures as postscript files; it needs standard MNRAS style file and epsf macro for figures. Paper submitted to MNRA