A pilot search for MeV gamma-ray emission from five galaxy clusters using archival COMPTEL data

Abstract

We search for MeV gamma-ray emission between 0.75-30 MeV from five galaxy clusters, viz. Coma, VIRGO, SPT-CL J2012-5649, Bullet, and El Gordo, using archival data from the COMPTEL telescope. For this purpose we use three search templates: point source, radial disk and radial Gaussian. We do not detect any signals from Coma, SPT-CL J2012-5649, Bullet and El Gordo clusters with the 95\% c.l. photon energy flux limit $\sim 10^{-10} ~\rm{erg /cm^2/s} $. For VIRGO, we detect a non-zero signal between 0.92 to 1.63 MeV having marginal significance of about $2.5\sigma$, with the observed energy flux $ \sim 10^{-9}~\rm{ergs/cm^2/s}$. However, we do not confirm the previously reported evidence in literature for a gamma-ray line from Coma and VIRGO clusters between 5-7 MeV.