A COMPARISON OF DIRECT N-BODY INTEGRATION WITH ANISOTROPIC GASEOUS MODELS OF STAR-CLUSTERS

We compare the results for the dynamical evolution of star clusters de rived from anisotropic gaseous models with the data from N-body simula tions of isolated and one-component systems, each having a modest numb er of stars. The statistical quality of N-body data was improved by av eraging results from many N-body runs, each with the same initial para meters but with different sequences of random numbers used to initiali ze the positions and velocities of the particles. We study the develop ment of anisotropy, the spatial evolution and energy generation by thr ee-body binaries and its N-dependence. We estimate the following free parameters of anisotropic gaseous models: the time-scale for collision al decay of anisotropy and the coefficient in the formulae for energy generation by three-body binaries. To achieve a reasonable agreement b etween N-body and gaseous models for the core in pre- as well as in po st-collapse, only the energy generation by binaries had to be varied w ith N. Anisotropy influences the dynamical evolution and kinematic str ucture of the cluster for the intermediate and outer regions.