Dynamics of Fe bubbles in young supernova remnants

Observations of core-collapse supernovae (SNe) have revealed the presence o f extensive mixing of radioactive material in SN ejecta. The mixing of radi oactive material, mostly freshly synthesized Ni, is not complete, which lea ds to a two-phase SN ejecta structure. The low-density phase consists of Fe bubbles, created by the energy input from radioactive Co and Ni, surrounde d by compressed high-density metal-rich ejecta. We report on the theoretica l investigation of supernova remnant (SNR) dynamics. with the two-phase SN ejecta. We first present three-dimensional hydrodynamic simulations of a si ngle Fe bubble immersed in an outer ejecta envelope. We then consider rando mly distributed Fe bubbles with an average volume filling fraction of 1/2. We find that the presence of Fe bubbles leads to vigorous turbulence and mi xing of Fe with other heavy elements and with the ambient normal-abundance, gas. The turbulent energy can be an order of magnitude larger than in the case of smooth ejecta. A significant fraction of the shocked ejecta is foun d in narrow filaments and clumps moving with radial velocities larger than the velocity of the forward shock. Observational consequences of the two-ph ase ejecta on SNR X-ray spectra and images are briefly mentioned.