Speaker
Description
When propagating through the universe, gamma rays at very-high energy (VHE, $E > 100$ GeV) and ultra-high energy cosmic rays (UHECR) can interact with the optical to microwave photon fields that permeate the cosmic voids. These interactions result in a characteristic absorption imprint in the spectra of extragalactic gamma-rays sources at VHE, and in a change in mass-composition of the observed spectrum of UHECR. The study of both VHE gamma rays and UHECR therefore requires precise knowledge of the intensity of the cosmic photon fields. In this talk, we explore the impact of the current uncertainties on the optical and infrared photon fields, the extragalactic background light (EBL) on the propagation of astroparticles. We restrict the range of available EBL models to those best matching the recent measurements, and compare the different reconstructions resulting from these models. We find that the knowledge on the cosmic backgrounds is no longer the dominant source of uncertainties in understanding the phenomenology of astroparticle sources, enabling robust spectral and composition inference with the next generation of both gamma-ray and UHECR measurements.
