Diffuse gamma-ray and neutrino emission from the Milky Way and the local knee in the cosmic ray spectrum

As cosmic rays propagate through the Galaxy, they produce gamma rays and contribute to the gamma-ray background. The authors compute the expected gamma-ray background based on the observed cosmic ray flux. They show an overproduction of gamma-ray above 100 TeV, which they suggest is due to the rarity of 1 PeV cosmic-ray sources. Their work helps constrain the sources of high energy cosmic rays.