Matter mixing in core-collapse supernova ejecta : large density perturbations in the progenitor star?

Matter mixing is one important topic in the study of core-collapse supernova (CCSN) explosions. In this paper, we perform two-dimensional hydrodynamic simulations to reproduce the high velocity ^{56} Ni clumps observed in SN 1987A. This is the first time that large density perturbation is proposed in the CCSN progenitor to generate Rayleigh–Taylor (RT) instability and make the effective matter mixing. In the case of a spherical explosion, RT instability is efficient at both C+O/He and He/H interfaces of the SN progenitor. Radial coherent structures shown in perturbation patterns are important for obtaining high velocity ^{56} Ni clumps. We can also obtain matter mixing features and high velocity ^{56} Ni clumps in some cases of aspherical explosion. We find that one of the most favorable models in our work has a combination of bipolar and equatorially asymmetric explosions in which at least 25% of density perturbation is introduced at different composition interfaces of the CCSN progenitor. These simulation results are comparable to the observational findings of SN 1987A.