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Abstract Galaxy clusters could produce gamma-rays from inverse Compton scattering of cosmic ray electrons or hadronic interactions of cosmic ray protons with the intracluster medium. It is still an open question on whether gamma-ray emission (> GeV energies) has been detected from galaxy clusters. We carry out a systematic search for gamma-ray mission based on 300 galaxy clusters selected from the 2500 deg 2 SPT-SZ survey after sorting them in descending order of M 500 / z 2 , using about 15 years of Fermi-LAT data in the energy range between 1–300 GeV. We were able to detect gamma-ray emission with significance of about 6.1σ from one cluster, viz. SPT-CL J2012-5649. The estimated photon energy flux from this cluster is approximately equal to 1.3 × 10 -6 MeV cm -2 s -1 . The gamma-ray signal is observed between 1–10 GeV with the best-fit spectral index equal to -3.61 ± 0.33. However, since there are six radio galaxies spatially coincident with SPT-CL J2012-5649 within the Fermi-LAT PSF, we cannot rule out the possibility this signal could be caused by some of these radio galaxies. Six other SPT-SZ clusters show evidence for gamma-ray emission with significance between 3–5σ. None of the remaining clusters show statistically significant evidence for gamma-ray emission.
Manna et al. (2024) studied this question.