Galaxy clusters in high definition: a dark matter search

TL;DR

This paper demonstrates that galaxy clusters, despite their diffuse radio backgrounds, can provide competitive constraints on dark matter properties, especially WIMP masses below 700 GeV, by analyzing high-resolution radio data.

Contribution

It re-evaluates galaxy clusters as dark matter search targets using extrapolated surface brightness profiles, showing they can outperform dwarf galaxies in certain conditions.

Findings

Clusters can exclude WIMPs below 700 GeV annihilating to b-quarks.

Extrapolated Coma data offers strong constraints with lower magnetic field uncertainties.

Clusters' inner halo profiles clash with radio halo shapes, aiding dark matter detection.

Abstract

Recent radio-frequency probes, with the ATCA and ASKAP telescopes, have proven themselves to be at the forefront of placing indirect limits on the properties of dark matter. The latter being able to substantially exceed the constraining power of Fermi-LAT data. However, these observations were based only on dwarf galaxies, where magnetic field uncertainties are large. Here we re-examine the case for galaxy clusters, often ignored due to substantial diffuse radio backgrounds, by considering the extrapolation of known cluster surface brightness profiles down to scales observable with MeerKAT. Despite large baryonic backgrounds, we find that clusters can be competitive with dwarf galaxies. Extrapolated Coma data being able to rule out WIMPs of mass $< 700$ GeV annihilating via $b$-quarks. This is while having lesser uncertainties surrounding the magnetic field and diffusive environment. Such compelling results are possible due to a clash between the inner shape of the dark matter halo and the flat inner profile of radio halos which is most pronounced for NFW-like Einasto profiles, the presence of which having some supporting evidence in the literature.