Effect of Streaming Motion of Baryons Relative to Dark Matter on the Formation of the First Stars

TL;DR

This study uses cosmological simulations to assess how supersonic baryon-dark matter streaming velocities influence the formation of the first stars, finding minimal impact on gas evolution and star formation.

Contribution

It provides the first detailed simulation-based analysis showing that streaming velocities have negligible effects on early star formation processes.

Findings

Streaming velocities have little effect on gas evolution at z<50.

Star formation proceeds similarly regardless of initial streaming velocities.

Reionization is dominated by large halos unaffected by streaming velocities.

Abstract

We evaluate the effect of a supersonic relative velocity between the baryons and dark matter on the thermal and density evolution of the first gas clouds at z < 50. Through a series of cosmological simulations, initialized at z=100 with a range of relative streaming velocities and minihalo formation redshifts, we find that the typical streaming velocities will have little effect on the gas evolution. Once the collapse begins, the subsequent evolution of the gas will be nearly indistinguishable from the case of no streaming, and star formation will still proceed in the same way, with no change in the characteristic Pop III stellar masses. Reionization is expected to be dominated by halo masses of > 10^8 M_sun, for which the expected effect of streaming is negligible.