Diffuse emission from stochastic sources

Diffuse emission in gamma-rays and neutrinos are produced by the interaction of cosmic rays with the interstellar medium. Below some hundreds of TeV, the sources of these cosmic rays are most likely Galactic. Hence, observations of high-energy gamma-rays and neutrinos can be used to probe the flux of cosmic rays in other parts of the Galaxy. Supernova remnants are usually considered as the prime candidate for the acceleration of Galactic cosmic rays. They inject cosmic rays in a point-like and specific time-dependent manner. As the precise positions and ages of the sources are not known, predictions must be obtained in a stochastic model. At GeV energies, the distribution of sources can be approximated with a smoothly varying spatial and temporal source density. At hundreds of TeV, however, the point-like nature matters as less sources contribute effectively due to shorter escape times. We have modelled diffuse emissions at hundreds of TeV, relevant for measurements by LHAASO, Tibet AS-gamma, IceCube, and the upcoming SWGO, as well as at tens of GeV, as measured by Fermi-LAT. This reveals the distinctive nature of diffuse emissions at the respective energies which can likely be used to constrain source models and locate cosmic ray sources.