Supersonic cloud collision. II

Abstract

Aims. In this second paper of the sequel of two papers, we continue to investigate the problem of molecular cloud (MC) collision. The companion paper to this one considered highly supersonic cloud collisions and examined the effect of bending and shearing instabilities on the shocked gas slab. We now consider moderately supersonic cloud collisions (precollision cloud velocities from 1.2 km s(-1) to 2.4 km s(-1)).

Methods. In the current paper, we present five SPH simulations of fast head-on and/or off-centre cloud collisions to study the evolution of a ram-pressure confined gas slab. The relevant thermodynamical details of the problem have been simplified by adopting a simple barytropic equation of state. We explore the parameter space by varying the pre-collision velocity and the temperature of the post collision gas slab.

Results. Slab temperature appears to play a key role in its dynamical evolution. The pressure-confined gas slab becomes Jeans unstable if the average sound crossing time, t(cr), of putative clumps condensing out of it is much longer than their respective freefall time, t(ff). Self gravitating clumps may spawn multiple/larger N-body star clusters. Warmer gas slabs are less likely to fragment and may simply end up as diffuse gas clouds.