Gamma-rays from Nearby Clusters: Constraints on Selected Decaying Dark Matter Models

Understand

Recently, the Fermi-LAT collaboration reported upper limits on the GeV gamma-ray flux from nearby clusters of galaxies.

• Motivated by these limits, we study corresponding constraints on gamma-ray emissions from two specific decaying dark matter models, one via grand unification scale suppressed operators and the other via R-parity violating operators.
• Both can account for the PAMELA and Fermi-LAT excesses of e^\pm.
• For GUT decaying dark matter, the gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to 10 GeV, lead to the most stringent constraints to date.