WIMP DM and first stars: suppression of fragmentation in primordial star formation

TL;DR

This study uses 3D simulations to show that dark matter annihilation heating suppresses fragmentation in primordial star formation, leading to more stable protostellar discs and fewer multiple star systems.

Contribution

First 3D simulations incorporating dark matter annihilation feedback during primordial mini-halo collapse, revealing its stabilizing effect on protostellar discs.

Findings

Dark matter annihilation heats gas but does not prevent collapse.

Protostellar discs become stable and less prone to fragmentation.

Fragmentation, when it occurs, results in wide binary systems.

Abstract

We present the first 3D simulations to include the effects of dark matter annihilation feedback during the collapse of primordial mini-halos. We begin our simulations from cosmological initial conditions and account for dark matter annihilation in our treatment of the chemical and thermal evolution of the gas. The dark matter is modelled using an analytical density profile that responds to changes in the peak gas density. We find that the gas can collapse to high densities despite the additional energy input from the dark matter. No objects supported purely by dark matter annihilation heating are formed in our simulations. However, we find that the dark matter annihilation heating has a large effect on the evolution of the gas following the formation of the first protostar. Previous simulations without dark matter annihilation found that protostellar discs around Population III stars rapidly fragmented, forming multiple protostars that underwent mergers or ejections. When dark matter annihilation is included, however, these discs become stable to radii of 1000 AU or more. In the cases where fragmentation does occur, it is a wide binary that is formed.