Dust Destruction in the High-Velocity Shocks Driven by Supernovae in the Early Universe

We investigate the destruction of dust grains by sputtering in the high-velocity interstellar shocks driven by supernovae (SNe) in the early universe to reveal the dependence of the timescale of dust destruction on the gas density n_H,0 in the interstellar medium (ISM), as well as on the progenitor mass M_pr and explosion energy E₅₁ of SNe. The sputtering yields for the combinations of dust and ion species of interest to us are evaluated by applying the so-called universal relation with a slight modification. The dynamics of dust grains and their destruction by sputtering in shocks are calculated by taking into account the size distribution of each dust species, together with the time evolution of the temperature and density of the gas in spherically symmetric shocks. The results of the calculations show that the efficiency of dust destruction depends not only on the sputtering yield but also on the initial size distribution of each grain species. The efficiency of dust destruction increases with increasing E₅₁ and/or increasing n_H,0 but is almost independent of M_pr as long as E₅₁ is the same. The mass of gas swept up by a shock is an increasing function of E₅₁ and a decreasing function of n_H,0. Combining these results, we present the approximation formula for the timescale of destruction for each grain species in the early universe as a function of E₅₁ and n_H,0. This formula is applicable for investigating the evolution of dust grains at the early epoch of the universe with the metallicity of Z<~10^-3 Z_solar. The effects of the cooling processes of gas on the destruction of dust are briefly discussed.