Dust Destruction by the Reverse Shock in the Cassiopeia A Supernova
  Remnant
  Core collapse supernovae (CCSNe) are important sources of interstellar dust,
potentially capable of producing one solar mass of dust in their explosively
expelled ejecta. However, unlike other dust sources, the dust has to survive
the passage of the reverse shock, generated by the interaction of the supernova
blast wave with its surrounding medium. Knowledge of the net amount of dust
produced by CCSNe is crucial for understanding the origin and evolution of dust
in the local and high-redshift universe. Our aim is to identify the dust
destruction mechanisms in the ejecta, and derive the net amount of dust that
survives the passage of the reverse shock. We use analytical models for the
evolution of a supernova blast wave and of the reverse shock, with special
application to the clumpy ejecta of the remnant of Cassiopeia A. We assume that
the dust resides in cool oxygen-rich clumps that are uniformly distributed
within the remnant and surrounded by a hot X-ray emitting plasma, and that the
dust consists of silicates (MgSiO3) and amorphous carbon grains. The passage of
the reverse shock through the clumps gives rise to a relative gas-grain motion
and also destroys the clumps. Inside the ejecta clouds, dust is processed via
kinetic sputtering, which is terminated either when the grains escape the
clumps, or when the clumps are destroyed by the reverse shock. In either case,
grain destruction proceeds thereafter by thermal sputtering in the hot ambient
gas. We find that 11.8% and 15.9% of, respectively, the silicate and carbon
dust survives the passage of the reverse shock by the time the shock has
reached the center of the remnant. These fractions depend on the morphology of
the ejecta and the medium into which the remnant is expanding, as well as the
composition and size distribution of the grains that formed in the ejecta.
Results will therefore differ for different types of supernovae.
