Galactic gamma-ray background radiation from supernova remnants

The contribution of the source cosmic rays (SCRs), confined in supernova remnants, to the diffuse high-energy gamma-ray emission above 1 GeV from the Galactic disk is studied. Gamma-rays produced by the SCRs have a much harder spectrum compared with those generated by the Galactic cosmic rays that occupy a much larger residence volume uniformly. SCRs contribute less than 10% at GeV energies and become dominant at gamma-ray energies above 100 GeV. The contributions from pi(0)-decay and inverse Compton gamma-rays have comparable magnitude and spectral shape, whereas the bremsstrahlung component is negligible. At TeV energies the contribution from SCRs increases the expected diffuse gamma-ray flux by almost an order of magnitude. It is shown that for the inner Galaxy the discrepancy between the observed diffuse intensity and previous model predictions at energies above a few GeV can be attributed to the SCR contribution.