Collision between molecular clouds - III: the effects of cloud initial density profile on head-on collisions

Abstract

In this third paper of our cloud collision series, we present the results from simulations of head-on collisions with a strongly centrally condensed initial density profile of rho proportional to R-2. We investigate the impact of these density profiles on the overall evolution of the simulations: the structures formed, their dynamical evolution, and their star formation activity. We consider clouds that are globally bound and globally unbound, leading to three different scenarios - the collision of a bound cloud with a bound cloud, the collision of two unbound clouds, or the collision of one cloud of each type. In all the simulations, dense star clusters form before the collisions occur, and we find that star formation remains confined to these systems and is little affected by the collisions. If the clouds are both initially bound, the collision forms a filamentary structure, but otherwise this does not occur. We observe that rotating structures form around the clusters, but they also form in our non-colliding control simulations, so are not a consequence of the collisions. The dissipation of kinetic energy in these simulations is inefficient because of the substructure created in the clouds by turbulence before the collisions. As a result, although some gas is left bound in the COM frame, the star clusters formed in the simulations do not become bound to each other.