DESTRUCTION OF INTERSTELLAR DUST IN EVOLVING SUPERNOVA REMNANT SHOCK WAVES

Abstract

Supernova generated shock waves are responsible for most of the destruction\nof dust grains in the interstellar medium (ISM). Calculations of the dust\ndestruction timescale have so far been carried out using plane parallel steady\nshocks, however that approximation breaks down when the destruction timescale\nbecomes longer than that for the evolution of the supernova remnant (SNR)\nshock. In this paper we present new calculations of grain destruction in\nevolving, radiative SNRs. To facilitate comparison with the previous study by\nJones et al. (1996), we adopt the same dust properties as in that paper. We\nfind that the efficiencies of grain destruction are most divergent from those\nfor a steady shock when the thermal history of a shocked gas parcel in the SNR\ndiffers significantly from that behind a steady shock. This occurs in shocks\nwith velocities >~ 200 km/s for which the remnant is just beginning to go\nradiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust\ndestruction timescales are increased by a factor of ~2 compared to those of\nJones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of\nsupernova rates and ISM mass lead to another factor of ~3 increase in the\ndestruction timescales, resulting in a silicate grain destruction timescale of\n~2-3 Gyr. These increases, while not able resolve the problem of the discrepant\ntimescales for silicate grain destruction and creation, are an important step\ntowards understanding the origin, and evolution of dust in the ISM.\n