Discrete sources of cosmic gamma rays

Abstract

The possibility is considered that some unidentified gamma-ray sources are in fact not discrete sources but rather 'apparent sources' caused by cosmic-ray irradiation of the clumpy interstellar medium. It is shown that six of nine unidentified gamma-ray sources in the 2CG catalog can be explained in terms of the mechanism considered and that the six apparent sources are associated with molecular cloud complexes. It is concluded that much of the galactic gamma radiation arises from the interaction of cosmic rays with the interstellar medium.