COMPTEL IMAGING OF THE GALACTIC DISK AND THE SEPARATION OF DIFFUSE EMISSION AND POINT SOURCES

The first MeV image of the inner Galaxy obtained with the COMPTEL telescope aboard the Compton Gamma-Ray Observatory shows a structured ridge of emission along the Galactic equator which probably consists of diffuse radiation and unresolved discrete sources. The intensity distribution of this ridge distinctly differs from the expected distribution for a simple model of the diffuse radiation. Most remarkable are the observed excursions out of the disk, which may hint at the presence of gamma-ray point sources located several degrees away from the mid-plane, but a diffuse origin cannot be excluded. If these are indeed discrete sources, a substantial fraction of the unresolved emission along the disk may not be of diffuse origin, with an ensemble of sources hidden in the observed ridge.