Dynamical evolution of star clusters in tidal fields
Abstract
We report results of a large set of Nbody calculations aimed to study the evolution of multimass star clusters in external tidal fields. Our clusters start with the same initial massfunctions, but varying particle numbers, orbital types and density profiles. Our main focus is to study how the stellar massfunction and other cluster parameters change under the combined influence of stellar evolution, twobody relaxation and the external tidal field. We find that the lifetimes of star clusters moving on similar orbits scale as T sim T_RH^x, where T_RH is the relaxation time, and the exponent x depends on the initial concentration of the cluster and is around x approx 0.75. From the results for the lifetimes, we predict that between 53% to 67% of all galactic globular clusters will be destroyed within the next Hubble time. Lowmass stars are preferentially lost and the depletion is strong enough to turn initially increasing massfunctions into massfunctions which decrease towards the lowmass end. The details of this depletion are insensitive to the starting condition of the cluster. The preferential depletion of lowmass stars from star clusters leads to a decrease of their masstolight ratios except for a short period close to final dissolution. The fraction of compact remnants is increasing throughout the evolution and they are more strongly concentrated towards the cluster cores than mainsequence stars. For a sample of galactic globular clusters with well observed parameters, we find a correlation between the observed slope of the massfunction and the lifetimes predicted by us. It seems possible that galactic globular clusters started with a massfunction similar to what one observes for the average massfunction of the galactic disc and bulge. (Abridged)
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2003
 DOI:
 10.1046/j.13658711.2003.06286.x
 arXiv:
 arXiv:astroph/0211471
 Bibcode:
 2003MNRAS.340..227B
 Keywords:

 stellar dynamics;
 methods: Nbody simulations;
 globular clusters: general;
 Astrophysics
 EPrint:
 22 pages, 26 figures,accepted for publication in MNRAS