On the DM interpretation of the origin of non-thermal phenomena in galaxy clusters

TL;DR

This study evaluates whether dark matter annihilation models can explain non-thermal phenomena in galaxy clusters, finding that only low-mass neutralino models with specific density profiles are plausible, but require additional factors like substructure boosts.

Contribution

It provides a comprehensive analysis of different neutralino dark matter models against multi-frequency observations of the Coma cluster, highlighting the limitations and conditions for DM-based explanations.

Findings

High-mass DM models overpredict emissions across frequencies.

Low-mass DM models are more consistent with observations.

DM annihilation heating exceeds gas cooling in NFW profiles.

Abstract

(Abridged) We study the predictions of various annihilating Dark Matter (DM) models in order to interpret the origin of non-thermal phenomena in galaxy clusters. We consider three neutralino DM models with light (9 GeV), intermediate (60 GeV) and high (500 GeV) mass. The secondary particles created by neutralino annihilation produce a multi-frequency Spectral Energy Distribution (SED), as well as heating of the intracluster gas, that are tested against the observations available for the Coma cluster. The DM produced SEDs are normalized to the Coma radio halo spectrum. We find that it is not possible to interpret all non-thermal phenomena observed in Coma in terms of DM annihilation. The DM model with 9 GeV mass produces too small power at all frequencies, while the DM model with 500 GeV produces a large excess power at all frequencies. The DM model with 60 GeV and $\tau^{\pm}$ composition is consistent with the HXR and gamma-ray data but fails to reproduce the EUV and soft X-ray data. The DM model with 60 GeV and $b{\bar b}$ composition is always below the observed fluxes. The radio halo spectrum of Coma is well fitted only in the $b{\bar b}$ or light and intermediate mass DM models. The heating produced by DM annihilation in the center of Coma is always larger than the intracluster gas cooling rate for an NFW DM density profile and it is substantially smaller than the cooling rate only for a cored DM density profile in DM model with 9 GeV. We conclude that the possibility of interpreting the origin of non-thermal phenomena in galaxy clusters with DM annihilation models requires a low neutralino mass and a cored DM density profile. If we then consider the multimessenger constraints to the neutralino annihilation cross-section, it turns out that such scenario would also be excluded unless we introduce a substantial boost factor due to the presence of DM substructures.