Cosmic-ray transport and gamma-ray emission in M31

We study the possibility that an extended cosmic-ray leptonic and/or hadronic halo is at origin of large-scale gamma-ray emission detected from Andromeda Galaxy (M31). consider a broad ensemble non-homogeneous diffusion scenarios and injection sources. find electrons protons could be, very likely are, responsible for part, or all, M31, including out to more than 100 kpc center galaxy. also simulate possible pulsars in effect regions highly inefficient around acceleration sites, as suggested by recent TeV observations with Cherenkov telescopes.