Grain Survival in Supernova Remnants and Herbig-Haro Objects

Abstract

By using the flux ratio [FeII]8617/[OI]6300, we demonstrate that most of the interstellar dust grains survive in shocks associated with supernova remnants and Herbig-Haro objects. The [FeII]/[OI] flux ratio is sensitive to the gas-phase Fe/O abundance ratio, but is insensitive to the ionization state, temperature, and density of the gas. We calculate the [FeII]/[OI] flux ratio in shocks, and compare the results with the observational data. When only 20% of iron is in the gas phase, the models reproduce most successfully the observations. This finding is in conflict with the current consensus that shocks destroy almost all the grains and 100% of metals are in the gas phase. We comment on previous works on grain destruction, and discuss why grains are not destroyed in shocks.Comment: 8 pages (AASTex v5.0), 3 figures. To be published in ApJ Letters (accepted 3/10/2000