Exploring Cosmic Rays Ionization Power

Abstract

The latest generations of telescopes have revealed a rich sky at high and very high energies. The most abundant identified sources are active galactic nuclei, usually blazars. It has been established that the Extra-galactic Background Light (optical to infrared wavelengths) attenuates high-energy photons through pair production. The development of pair-photon cascades along the line of sight modiies the originally emitted spectrum and have a measurable impact onto the source extent and arriving time of the photons. These effects should be included in our interpretation of the observations in order to progress in the understanding of the physical origin of the emission. We follow the three-dimensional trajectories of such cascades through numerical simulations. We report here the status of our investigations regarding the gamma-ray propagation through a ∼ 100 Mpc scale. Thisindirect study of the background photon ields and the extra-galactic magnetic ield (EGMF) is an exciting aspect of what some authors already call gamma-ray cosmology.