Detailed study of extended γ-ray morphology in the vicinity of the Coma cluster with Fermi Large Area Telescope

Galaxy clusters can be sources of high-energy (HE) γ-ray radiation due to the efficient acceleration of particles exceeding EeV energies. At present, though, the only candidate for emitting HE γ-rays is the Coma cluster, towards which an excess of γ-ray emission has been detected by the Fermi Large Area Telescope (Fermi-LAT). Using ∼12.3 yr of Fermi-LAT data, we explored the region of the Coma cluster between energies 100 MeV and 1 TeV by detailed spectral and morphological analysis. In the region of the Coma cluster, we detected diffuse γ-ray emission of energies between 100 MeV and 1 TeV with a 5.4σ extension significance and a 68 per cent containment radius of 0.82+0.10-0.05 degrees derived with a two-dimensional homogeneous disc model. The corresponding γ-ray spectrum extends up to ∼50 GeV, with a power-law index of Γ = 2.23 ± 0.11 and flux of (3.84± 0.67)× 10⁻¹²\, erg\, cm⁻²\, s⁻¹. Using energy arguments we show that point-like sources such as radiogalaxies and star-forming galaxies are unlikely to explain the emission, and more likely, the emission is produced in the Coma cluster. Besides, we also identified three point-like sources in the region. However, because of limited statistics, we could neither exclude nor confirm the contribution of three point-like sources to the total emissions.