Analysis of the kinematics of ejecta created after a catastrophic collision

•A new analysis of hydrocode models of asteroid families formation is shown.•Peculiar and unexpected features of such models have been revealed.•Hydrocodes can produce fragments colliding without intervention of mutual gravity.•Such properties could trigger the ordered reaccumulation of the fragments.

According to the results of hydrodynamical simulations, the creation of an asteroid dynamical family as the outcome of a high-energy collision consists of the partial or complete shattering of the parent body followed by re-accumulation of many fragments into larger bodies due to the mutual gravity. This scenario seems to reproduce satisfactorily the observed properties of the asteroid families, and in particular the size distribution of the members. In this paper we show a preliminary analysis of the ejection velocity fields predicted by hydrodynamical models, in comparison with the ejection velocity fields simulated by semi-empirical models, in order to identify the features of the velocity distribution that trigger or prevent the fragments’ gravitational re-accumulation.