Abundance Distribution in Supernova Remnant Cas A

Two dimensional hydrodynamical simulations of supernova remnant Cas A are performed starting from the onset of explosion to the present phase. Before the explosion, distributions of circumstellar medium is constructed, where the medium is assumed to be ejected from a progenitor. A supernova simulation is carried out by two dimensional hydrodynamical calculation. It is found that the Rayleigh-Taylor instability is advanced from the boundary between hydrogen and helium layers. The instability from silicon and iron layers is not grown enough to induce the observed mixing of materials. It is suggested that mixing before the explosion and/or instability at the boundary of silicon and iron layers due to different distributions of circumstellar medium is needed to explain the observations