Photons as carriers of ultra-high energy in cosmic space

Abstract

Absorbing process of ultrahigh-energy gamma-quanta in a cosmic space is investigated. It is shown that the main absorbing mechanism is the reactions arising at collisions of cosmic-ray photons with microwave and radio background ones. Estimate of the mean free path of a photon for different energies gives evidence that gamma-quanta with energies E>1019 eV running from Active Galactic Nuclei seem to reach the Earth vicinity. This result is in agreement with the recent observations of extensive air shower array experiments realized by AGASA and Yakutsk.