Constraints on top-down models for the origin of UHECRs from the Pierre Auger Observatory data

Abstract

Taking into account the Pierre Auger Observatory limits on the photon fraction among the highest energy cosmic rays, we show that the models based on the decay of super-heavy dark matter in the halo of our Galaxy are essentially excluded from being the sources of UHECRs unless their contribution becomes significant only above 100 EeV. Some top-down models based on topological defects are however compatible with the current data and may be best constrained in the future by the high-energy neutrino flux limit.