The Evolution of Star Clusters

The method for computing the evolution of star clusters which was developed in a previous paper (Larson I970) is here applied to calculating the evolution of a number of different models of star clusters. As in Paper I, the calculations refer only to the special case of equal masses, the stars all being assumed to have a mass of IM_⊙ . Three types of systems are considered, and their evolution is described in some detail: ( I ) a globular cluster of mass $$2\,\times\,{10}^{5}\,{M}_{\odot}$$ , ( 2 ) a galactic cluster of mass 100 M_⊙ , and (3) a dense galactic nucleus of mass $${10}^{8}\,{M}_{\odot}$$ In general, the results are in fair agreement with the predictions of classical relaxation theory, except that in some respects the classical picture is seen to be over-simplified. Some of the principal conclusions of the project are ( I ) the rate of evolution and the stellar escape rate are quite sensitive to the structure of the system; (2) the velocity distribution always tends to become strongly anisotropic in the outer part of the system; and (3) the existence of a tidal limit has a strong effect on the escape rate, and may increase it by a large factor compared to an isolated cluster.