Influence of the Stellar Mass Function on the Evaporation Rate of Tidally Limited Postcollapse Globular Clusters

Abstract

We study the rate of escape of stars (``evaporation'') from tidally-limited postcollapse globular clusters having a power-law distribution of stellar masses. We use a multi-mass Fokker-Planck code and assume a steady tidal field. Stellar-dynamical processes cause the inner parts of the cluster to expand, which in turn causes stars to overflow the tidal boundary. Mass loss by stellar evolution is assumed to be unimportant in these later evolutionary stages. The fraction of the cluster mass lost per half-mass relaxation time ($\trh$) is roughly constant, in agreement with simple homologous models with equal-mass stars. If $\trh$ is computed in the conventional way from the mean stellar mass, however, a broad stellar mass function can double the loss of mass per $\trh$. We discuss implications of our results for the evolution of globular-cluster systems in our own and other galaxies. In particular, the number of Galactic clusters destroyed by evaporation alone may be as large or larger than the present cluster population.