Dust destruction and survival in the Cassiopeia A reverse shock

Abstract

ABSTRACT Core-collapse supernovae (CCSNe) produce large ($\gtrsim0.1\,{\rm M}_\odot$) masses of dust, and are potentially the primary source of dust in the Universe, but much of this dust may be destroyed before reaching the interstellar medium. Cassiopeia A (Cas A) is the only supernova remnant where an observational measurement of the dust destruction efficiency in the reverse shock is possible at present. We determine the pre- and post-shock dust masses in Cas A using a substantially improved dust emission model. In our preferred models, the unshocked ejecta contains $0.6\!-\!0.8\,{\rm M}_\odot$ of $0.1\,{\rm \mu m}$ silicate grains, while the post-shock ejecta has $0.02\!-\!0.09\,{\rm M}_\odot$ of $5\!-\!10 \, {\rm nm}$ grains in dense clumps, and $2 \times 10^{-3}\,{\rm M}_\odot$ of $0.1 \, {\rm \mu m}$ grains in the diffuse X-ray emitting shocked ejecta. The implied dust destruction efficiency is $74\!-\!94\,{\rm per\,cent}$ in the clumps and $92\!-\!98\,{\rm per\,cent}$ overall, giving Cas A a final dust yield of $0.05\!-\!0.30\,{\rm M}_\odot$. If the unshocked ejecta grains are larger than $0.1\,{\rm \mu m}$, the dust masses are higher, the destruction efficiencies are lower, and the final yield may exceed $0.5\,{\rm M}_\odot$. As Cas A has a dense circumstellar environment and thus a much stronger reverse shock than is typical, the average dust destruction efficiency across all CCSNe is likely to be lower, and the average dust yield higher. This supports a mostly stellar origin for the cosmic dust budget.