High Energy Diffuse Gamma-Rays from Galactic Plane

The dominant part of the diffuse gamma rays beyond 1 TeV from the Galactic plane has been thought as due to the inverse Compton scattering of interstellar photons with high-energy cosmic-ray electrons. In these energy regions, diffuse gamma-ray observations give us unique information on the energy spectrum of high-energy electron in the interstellar space, since we cannot observe those electrons directly. We made a calculation with |b|≤ 2◦ and |b|≤ 5◦for the diffuse gamma rays in the case of 3 spatial distribution in the Galaxy of cosmicray sources, and the results are compared with the most recent observed data by air shower experiments. We draw a restriction for the injection spectrum of high-energy electrons at the sources. It is also pointed out that patchy structure of the gamma-ray distribution will appear at high-energy side, if we observe the distribution with a higher angular resolution of a few arc degrees. This patchy structure will become distinct beyond 10TeV of IC gamma rays, where number of contributing sources of parent electrons decrease and their diffusion distance become smaller.