Propagation of Ultra–High‐Energy Protons through the Magnetized Cosmic Web

Abstract

If ultraYhigh-energy cosmic rays (UHECRs) originate from extragalactic sources, understanding the propagation of charged particles through the magnetized large-scale structure (LSS) of the universe is crucial in the search for the astrophysical accelerators. Based on a novel model of the turbulence dynamo, we estimate the intergalactic magnetic fields (IGMFs) in cosmological simulations of the formation of the LSS. Under the premise that the sources of UHECRs are strongly associated with the LSS, we consider a model in which protons with E � 10 19 eVare injected by sources that represent active galactic nuclei, located inside clusters of galaxies. With the model IGMFs, we then follow the trajectories of the protons, taking into account the energy losses due to interactions with the cosmic background radiation. For observers located inside groups of galaxies like ours, about 70% and 35% of UHECR events above 60 EeVarrive within � 15 � and � 5 � , respectively, of the source position with time delays of less than � 10 7 yr. This implies that the arrival direction of super-GZK protons might exhibit a correlation with the distribution of cosmologicalsourcesonthesky.Inthismodel,nearbysources(within10Y20Mpc)shouldcontributesignificantlytothe particle flux above � 10 20 eV. Subject headingg cosmic rays — large-scale structure of universe — magnetic fields — methods: numerical