Search for dark matter annihilation to gamma-rays from SPT-SZ selected galaxy clusters

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 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 σ . The best-fit dark matter mass and annihilation cross-section for this cluster are equal to (60.0 ± 11.8) GeV and ⟨ σv ⟩ = (6.0 ± 0.6) × 10 -25 cm 3 s -1 for the 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 σ , 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. ⟨ σv ⟩ = 6.44 × 10 -26 cm 3 s -1 for m χ = 10 GeV and b b ̅ annihilation channel.