Theoretical and observational agreement on mass dependence of cluster life times

Observations and N-body simulations both support a simple relation for the disruption time of a cluster as a function of its mass of the form: t(dis) = t(4) X (M/10(4) M-circle dot)(gamma). The scaling factor t(4) seems to depend strongly on the environment. Predictions and observations show that gamma similar or equal to 0.64 +/- 0.06. Assuming that t(dis) proportional to M-0.64 is caused by evaporation and shocking implies a relation between the radius and the mass of a cluster of the form: r(h) proportional to M-0.07, which has been observed in a few galaxies. The suggested relation for the disruption time implies that the lower mass end of the cluster initial mass function will be disrupted faster than the higher mass end, which is needed to evolve a young power law shaped mass function into the log-norma,l mass function of old (globular) clusters