Supersonic Cloud Collision - I

TL;DR

This paper investigates the dynamical evolution of shock-compressed gas slabs resulting from supersonic molecular cloud collisions, focusing on the effects of shear and including self-gravity using SPH simulations.

Contribution

It introduces a detailed simulation study of shear effects on shock-compressed slabs in molecular cloud collisions, incorporating self-gravity and different collision geometries.

Findings

Shear influences the stability and evolution of shock-compressed slabs.

Both head-on and off-centre collisions produce distinct dynamical behaviors.

Self-gravity significantly affects the collapse and fragmentation of the slabs.

Abstract

It has long been suggested that shocks might play an important role in altering the form of the interstellar medium (ISM). Shocks enhance gas density and sufficiently dense regions may become self gravitating. Potential star forming clouds within larger molecular clouds, move randomly at supersonic speeds. Depending on the precollision velocity, colliding molecular clouds produce a slab that is either shock compressed or pressure confined. In a sequel of two papers (I & II), we simulate molecular cloud collision and investigate the dynamical evolution of such slabs. Shocked slabs are susceptible to hydrodynamic instabilities and in the present paper (I) we study the effect of strong shear between slab layers on the dynamic evolution of a shock compressed gas slab. Both, head-on and off-centre cloud collisions have been examined in this work. We include self gravity in all our simulations. Simulations presented here, are performed using the smoothed particle hydrodynamics (SPH) numerical scheme. Individual, pre-collision clouds are modelled as pressure confined Bonnor-Ebert spheres. However, in the interest of brevity the thermodynamic details of the problem are simplified and the gas temperature is simply evolved by a barytropic equation of state. Obviously, the gas, to some extent suffers from thermal inertial effects. However, we note that the dynamical timescale is much smaller than the local sound crossing time so that such effects should have minimum influence.