High velocity dust grains produced by a supernova explosion

Abstract

Motivated by the discovery of a meteor with velocity more than 300~km/s (Afanasiev et al. 2007) we study how dust grains formed in the supernova (SN) ejecta at its free-expansion phase can keep their high velocity obtained from the gas, where these grains were born. Using a one-dimensional spherically symmetric Lagrangian approach we follow the dynamics of grains during the interaction of a SN ejecta with the ambient interstellar gas. We found that grains larger $\sim 0.3\mu$m can cross the SN forward shock front and reach the ambient interstellar medium. They are destroyed inefficiently, thus, their sizes remain close to the initial ones. In a diffuse interstellar gas of density $\lesssim 1$ cm${}^{-3}$ grains larger as $\gtrsim 1\mu$m move with velocity around $1-2$ thousand km/s and spread over distances exceeding $\sim 40-90$ pc from the SN origin within tens of kiloyears. In dense environment the propagation of grains is significantly suppressed: even large grains do not spread over distances greater than 50% of the current SN remnant size. Grains born close to the edge of the SN ejecta core in less-massive ejecta reach greater distances. Thus, high-velocity grains are expected to be formed in this part of the ejecta with mass lower than $\sim 3M_{\odot }$ of the SN remnant evolving in a diffuse gas with density $\lesssim 1$ cm${}^{-3}$. We discuss possible consequences for dust transport out from galactic disks.

18 pages, 12 figures