Search for Dark Matter Annihilation to gamma-rays from SPT-SZ selected Galaxy Clusters

TL;DR

This study searches for dark matter annihilation signals in gamma-ray data from galaxy clusters, finding some hints but no conclusive evidence, and setting upper limits on annihilation cross-sections.

Contribution

First comprehensive analysis of 16 years of Fermi-LAT data targeting 350 galaxy clusters for dark matter annihilation signals.

Findings

Largest signal at 3σ significance for one cluster, but inconsistent with dark matter models.

Set the most stringent upper limits on annihilation cross-section among galaxy clusters.

No definitive detection of dark matter annihilation signals.

Abstract

We search for dark matter annihilation from galaxy clusters in the energy range from 1-300 GeV using nearly 16 years of Fermi-LAT data. For this purpose, we use 350 galaxy clusters selected from the 2500 $\rm{deg^2}$ SPT-SZ survey. We model the dark matter distribution using the NFW profile for the main halo along with the Einasto profile for the substructure. The largest signal is seen for the cluster SPT-CL J2021-5257 with a significance of around $3\sigma$. The best-fit dark matter mass and annihilation cross-section for this cluster are equal to $(60.0 \pm 11.8)$ GeV and $\langle \sigma v \rangle= (6.0 \pm 0.6) \times 10^{-25} \rm{cm^3 s^{-1}}$ for the $\bar{b} b$ annihilation channel. However, this central estimate is in conflict with the limits on annihilation cross-section from dwarf spheroidal galaxies, and hence cannot be attributed to dark matter annihilation. Three other clusters show significance between $2-2.5\sigma$, whereas all the remaining clusters show null results. The most stringent 95\% c.l. upper limit for the WIMP annihilation cross-section among all the clusters is from SPT-CL J0455-4159, viz. $\langle \sigma v \rangle = 6.44 \times 10^{-26} \text{cm}^3 \text{s}^{-1}$ for $m_{\chi} = 10$ GeV and $b\bar{b}$ annihilation channel.