| Authors | Holger Baumgardt, Junichiro Makino |
|---|---|
| Affiliation | University of Tokyo |
| Accepted by | Monthly Notices of the Royal Astronomical Society |
| Contact | holger@astron.s.u-tokyo.ac.jp |
| URL | http://jp.arXiv.org/abs/astro-ph/0211471 |
| Links |
We find that the lifetimes of star clusters moving on similar orbits scale as T ~ TRHx, where TRH is the relaxation time, and the exponent x depends on the initial concentration of the cluster and is around x ~ 0.75. The scaling law does not change significantly if one goes from circular orbits to eccentric ones. 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. Low-mass stars are preferentially lost and the depletion is strong enough to turn initially increasing mass-functions into mass-functions which decrease towards the low-mass end. The details of this depletion are insensitive to the starting condition of the cluster and can be characterised as a function of a single variable, as e.g. the fraction of time spent until total cluster dissolution. The preferential depletion of low-mass stars from star clusters leads to a decrease of their mass-to-light ratios except for a short period close to final dissolution, when the mass-fraction in form of compact remnants starts to dominate. The fraction of compact remnants is increasing throughout the evolution. They are more strongly concentrated towards the cluster cores than main-sequence stars and their mass-fraction in the center can reach 95% or more around and after core-collapse. For a sample of galactic globular clusters with well observed parameters, we find a correlation between the observed slope of the mass-function and the lifetimes predicted by us. It seems possible that galactic globular clusters started with a mass-function similar to what one observes for the average mass-function of the galactic disc and bulge.