Primordial gas heating by dark matter and structure formation

TL;DR

This paper investigates how dark matter decays and annihilations heat primordial gas, potentially delaying structure formation and reducing star formation in small halos, with implications for early universe evolution.

Contribution

It introduces the impact of dark matter-induced heating on the critical halo mass and gas collapse, highlighting effects on early structure formation.

Findings

Dark matter heating increases the critical halo mass for collapse by up to a factor of 2.

Gas collapse in small halos is significantly reduced due to dark matter effects.

Dark matter processes may delay the formation of the first cosmic structures.

Abstract

Dark matter (DM) decays and annihilations might heat and partially reionize the Universe at high redshift. Although this effect is not important for the cosmic reionization, the gas heating due to DM particles might affect the structure formation. In particular, the critical halo mass for collapse is increased up to a factor of ~2. Also the fraction of gas which collapses inside the smallest halos is substantially reduced with respect to the cosmological value. These effects imply that DM decays and annihilations might delay the formation of the first structures and reduce the total star mass in the smallest halos.