Mass-Loss Timescale of Star Cluster in External Tidal Field

We investigate evolution of star clusters in steady external tidal field by means of N-body simulations. We followed several sets of cluster models whose strength and Coriolis's contribution of the external tidal field are different. We found that the mass loss timescale due to the escape of stars, t__mloss, and its dependence on the two-body relaxation timescale, t_rh,i, are determined by the strength of the tidal field. The logarithmic slope [≡ dln(t_mloss)/dln(t_rh,i)] approaches unity for the cluster models in weaker tidal fields. We also found that stronger Coriolis force against others, produced by parent galaxy whose density profile is shallower, makes the mass loss timescale longer. This is due to the fact that a fraction of stars whose orbit are nearly regular increases as the Coriolis force becomes stronger.