Grain Shattering in Shocks: The Interstellar Grain Size Distribution

摘要

We have studied the effects of shattering in grain-grain collisions. Based upon extensive numerical simulation of surface explosions and impacts, an analytical model has been developed which relates the final crater mass and fragment size distribution to the relative collision velocity, grain sizes, and material properties of projectile and target. Our model contains one free parameter, the critical shock pressure for shattering. This critical pressure corresponds to minimum collision velocities of approx. 1 km/s for shattering to occur. The shattering threshold is much smaller than the vaporization threshold, and we therefore conclude that shattering dominates over vaporization in grain-grain collisions. We present detailed results for grain destruction as a function of the grain size and composition. In particular, we consider MRN size distributions of silicate and carbonaceous (amorphous carbon/graphite) grains. We also present results for silicon carbide, diamond, iron, and ice test particles.