Gamma rays and astronomy

Gamma-ray observations of several galactic bodies are explored, relying on data from the OSO-3, SAS-2, and the COS-B spacecraft. The working hypothesis is that gamma ray emissivity is due to interactions of cosmic rays with interstellar gas, implying that the total gas increase is no more than a factor of 3 between 5-10 kpc from the galactic center. Regions of the galaxy known for gamma ray emissivity are defined, and noted to be in a spiral form with a pitch angle of about 13 deg. Observations of the local interstellar medium are constrained to regions void of point sources, and cosmic ray density measurements are employed to determine the total gas column density, as well as particular molecular cloud species. All point sources thus far observed, save one, are near the galactic plane, and aspects of the possible relationship between gamma ray sources and young and massive stars are explored.