Chinese Acad Sci, Inst High Energy Phys, Key Lab Particle Astrophys, Beijing 100049, Peoples R China
Aims. We calculate the attenuation of very high energy gamma rays from Galactic sources. Methods. A recent calculation of the Galactic interstellar radiation field shows that the infra-red radiation background near the Galactic Center is very intense. The attenuation of very high energy gamma rays by this radiation is strong and occurs at lower energies than previously thought. Results. Our result shows that the cutoff of the high energy gamma ray spectrum begins at about 20 TeV and reaches about 10% for 50 TeV gamma rays.