Core formation from self-heating dark matter

TL;DR

This paper proposes that self-heating processes in semi-annihilating dark matter can create cores in dwarf galaxy halos, addressing the density discrepancy between simulations and observations.

Contribution

It introduces a novel dark matter self-heating mechanism that forms cores in dwarf galaxies, especially effective in semi-annihilating scenarios with sub-GeV mass candidates.

Findings

Dark matter self-heating reduces inner halo density in dwarf galaxies.

Semi-annihilation effects are more significant in dwarf halos than larger ones.

The model suggests detectable signals in dark matter experiments for sub-GeV candidates.

Abstract

Cosmological simulations of the $\Lambda$CDM model suggest that the dark matter halos of dwarf galaxies are denser in their center than what observational data of such galaxies imply. In this letter, we propose a novel solution to this problem by invoking a certain class of dark matter self-heating processes. As we will argue, such processes lead to the formation of dark matter cores at late times by considerably reducing the inner mass density of dwarf-sized halos. For deriving concrete results, we focus on semi-annihilating dark matter scenarios and model the inner region of dark matter halos as a gravothermal fluid. An important aspect of this new solution is that the semi-annihilation effects are much more prominent in dwarf-sized halos than in the more massive halos that host galaxies and clusters, even if the corresponding cross sections are the same. Furthermore, the preferred parameter space for solving the small-scale problem suggests a thermal dark matter candidate with a mass below the GeV scale, which can be probed in dark matter direct and indirect detection experiments.