Gamma-rays from atomic and molecular gas in the first galactic quadrant

The fully sampled Columbia 1 deg CO survey and the Berkeley H I survey are compared with the COS B gamma-ray survey. As a first step, the study is limited to the high-energy gamma-rays (E greater than 300 MeV). It is found that a simple model, in which uniformly distributed cosmic rays interact with the interstellar gas, as traced by H I and CO, can account for almost all the observed gamma-rays. Furthermore, if the contribution from point sources to the gamma-ray flux is significant, these sources must have a galactic distribution similar to that of CO. The analysis permits calibration of the ratio between H2 column density and integrated CO line intensity: N(H2)/W(CO) = (1-3) 10 to the 20th molecules per sq cm k km per s.