Formation of stable non-gaussian velocity distribution on gravitational collapse and in merging process

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The results of collisionless n-body simulations are presented. We discuss the formation of the velocity distribution in collisionless n-body 3-dimensional system using GRAPE5. We caluculate two models, a spherical collapse and a cluster collision, and observe stable non-gaussian velocity distributions which are well fitted by equall-weight superposition of thermal distributions with various temperatures (DT). As for the spherical model, the velocity distributions are DT distyributions in all cases provided that the initial virial ratio is less than 0.23. As for the cluster collision model, the velocity distributions are in-isotropic and depnends on axis. These non-gaussian velocity distributions are formed well before the thermallization of the systems and stably persist for all the time within our numerical calculations. The appearance of non-Gaussian velocity distributions strongly depends on the initial virial ratio but have no connection with other parameters such as softening parameter, initial configrations or velocity distributions.
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