First star formation with dark matter annihilation

TL;DR

This study investigates the impact of dark matter self-annihilation energy on the formation of the first stars, finding minimal effects on the gas properties and star mass distribution.

Contribution

It introduces a model including dark matter annihilation energy into star formation simulations, showing limited influence on the initial mass function and collapse dynamics.

Findings

Dark matter annihilation slightly modifies gas chemistry during collapse.

The Jeans mass remains unchanged despite dark matter effects.

Collapse time increases by less than a few percent when annihilation energy is significant.

Abstract

We include an energy term based on Dark Matter (DM) self-annihilation during the cooling and subsequent collapse of the metal-free gas, in halos hosting the formation of the first stars in the Universe. We have found that the feedback induced on the chemistry of the cloud does modify the properties of the gas throughout the collapse. However, the modifications are not dramatic, and the typical Jeans mass within the halo is conserved throughout the collapse, for all the DM parameters we have considered. This result implies that the presence of Dark Matter annihilations does not substantially modify the Initial Mass Function of the First Stars, with respect to the standard case in which such additional energy term is not taken into account. We have also found that when the rate of energy produced by the DM annihilations and absorbed by the gas equals the chemical cooling (at densities yet far from the actual formation of a proto-stellar core) the structure does not halt its collapse, although that proceeds more slowly by a factor smaller than few per cent of the total collapse time.