The radial distribution of galactic gamma rays. III - The distribution of cosmic rays in the Galaxy and the CO-H2 calibration.

High-energy (>70 MeV) gamma-ray observations are compared to H I and CO surveys over more than half of the Milky Way. The kinematics of both H I and CO are used as a distance indicator to determine, in combination with COS-B gamma-ray data, the galacto-centric distribution of the gamma-ray emissivity (the production rate per H atom) for three gamma-ray energy intervals. The ratio between H₂ column density and integrated CO line intensity is calibrated independently of excitation and abundance effects. The galacto-centric distributions of cosmic-ray electrons and nuclei are derived separately from the gamma-ray emissivity distributions.