Star clusters containing massive central black holes. IV. Galactic tidal fields

Monte Carlo simulations of star cluster evolution are presented. The Monte Carlo scheme described previously is modified to incorporate a Galactic tidal radius r/sub t/, beyond which stars are stripped from the cluster. It is found that the late stages of cluster evolution are qualitatively unchanged by the introduction of a finite tidal cutoff. For clusters without a massive, central black hole the core collapses homologously with homology parameters independent of r/sub t/ and consistent with the recent findings of Cohn and of Lynden-Bell and Eggleton. For clusters possessing a central black hole, core collapse is eventually reversed by the heat flux from stellar disruption by the hole. The system attains a quasi-stationary, expanding state (by which time the hole has grown to several thousand solar masses). This state appears to be (roughly) independent of (i) the initial hole mass, (ii) the time during core evolution at which the hole is introduced and (iii) the value of r/sub t/. A simple homological model for core evolution with and without black holes is presented. The dynamical effects of those stars which diffuse outward during core collapse but are ''reencompassed'' during core reexpansion are incorporated. Numerical integrations of the resulting homological equations are in good agreement with the Monte Carlo ''data.'' When the homological equations are modified to include stellar ejections from the cusp due to occasional close encounters, the results are qualitatively unchanged. This finding suggests that the effects of close encounters in star cusps around massive black holes might not substantially alter results obtained with the present (Fokker-Planck) Monte Carlo scheme