Energy Dissipation in Interstellar Cloud Collisions
Abstract
We present a study of the kinetic energy dissipation in interstellar cloud collisions. The main aim is to understand the dependence of the elasticity (defined as the ratio of the final to the initial kinetic energy of the clouds) on the velocity and mass ratio of the colliding clouds, magnetic field strength, and gas metallicity for headon collisions. The problem has been studied both analytically and via numerical simulations. We have derived handy analytical relationships that well approximate the analogous numerical results. The main findings of this work are the following: (1) the kinetic energy dissipation in cloud collisions is minimum (i.e., the collision elasticity is maximum) for a cloud relative velocity v_{r} ~= 30 km s^{1} (2) the above minimum value is proportional ZL^{2}_{c}, where Z is the metallicity and L_{c} is the cloud size (the larger ZL^{2}_{c} is, the more dissipative, i.e., inelastic, the collision will be); and (3) in general, we find that the energy dissipation decreases when the magnetic field strength and mass ratio of the clouds are increased and the metallicity is decreased, respectively. We briefly discuss the relevance of this study to the global structure of the interstellar medium and to galaxy formation and evolution.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 1997
 DOI:
 10.1086/304401
 arXiv:
 arXiv:astroph/9702143
 Bibcode:
 1997ApJ...485..254R
 Keywords:

 Hydrodynamics;
 ISM: Clouds;
 ISM: Kinematics and Dynamics;
 numerical methods;
 Shock Waves;
 Astrophysics
 EPrint:
 16 pages, aasms LaTeX, 7 figures. ApJ, accepted