The mutual interaction between Population III stars and self-annihilating dark matter

Abstract

We use cosmological simulations of high-redshift minihaloes to investigate the effect of dark matter annihilation (DMA) on the collapse of primordial gas. We numerically investigate the evolution of the gas as it assembles in a Population III stellar disc. We find that when DMA effects are neglected, the disc undergoes multiple fragmentation events beginning at similar to 500 yr after the appearance of the first protostar. On the other hand, DMA heating and ionization of the gas speeds the initial collapse of gas to protostellar densities and also affects the stability of the developing disc against fragmentation, depending on the DM distribution. We compare the evolution when we model the DM density with an analytical DM profile which remains centrally peaked, and when we simulate the DM profile using N-body particles (the 'live' DM halo). When utilizing the analytical DM profile, DMA suppresses disc fragmentation for similar to 3500 yr after the first protostar forms, in agreement with earlier work. However, when using a 'live' DM halo, the central DM density peak is gradually flattened due to the mutual interaction between the DM and the rotating gaseous disc, reducing the effects of DMA on the gas, and enabling secondary protostars of mass similar to 1M(circle dot) to be formed within similar to 900 yr. These simulations demonstrate that DMA is ineffective in suppressing gas collapse and subsequent fragmentation, rendering the formation of long-lived dark stars unlikely. However, DMA effects may still be significant in the early collapse and disc formation phase of primordial gas evolution.