Dynamics of embedded protostar clusters in clouds

Abstract

The dynamics of clumps and protostars in a young protocluster system embedded in its parent molecular cloud are studied here through numerical simulations. It is found that the presence of massive clumps and their dynamics strongly affects the motion of the lower mass protostars. Mass segregation of clumps due to dynamical drag by the interclump gas results in the formation of a dense central region, and the lower mass protostars are preferentially ejected out of the cloud via gravitational encounters. The protostellar cluster is found to expand gradually with time, forming a more extended system than the clumps. Thus, embedded protostar clusters are probably dynamically evolved systems with large haloes of low-mass protostars. This explains observations of T Tauri stars, which appear to be isolated from active star-forming sites and are in regions devoid of dense gas. Since multiple star formation sites in clouds are common, outer members are subject to velocity perturbations due to massive clumps and other clusters, possibly leading to a faster removal of objects.