Pre-Collapse Evolution of Galactic Globular Clusters

Abstract

This paper is concerned with collisionless aspects of the early evolution of model star clusters. The effects of mass loss through stellar evolution and of a steady tidal field are modelled using $N$-body simulations. Our results (which depend on the assumed initial structure and the mass spectrum) agree qualitatively with those of Chernoff \& Weinberg (1990), who used a Fokker-Planck model with a spherically symmetric tidal cutoff. For those systems which are disrupted, the lifetime to disruption generally exceeds that found by Chernoff \& Weinberg, sometimes by as much as an order of magnitude. Because we do not model collisional effects correctly we cannot establish the fate of the survivors. In terms of theoretical interpretation, we find that tidal disruption must be understood as a loss of {\sl equilibrium}, and not a loss of {\sl stability}, as is sometimes stated.