The use of gamma rays to trace the local interstellar hydrogen

COS-B data in the latitude range 11° <¦b¦ < 19° show the gamma-ray intensity to be closely correlated with the total line-of-sight absorption derived from galaxy counts. It is found that to a good approximation the gamma-ray intensity is proportional to the total gas column density, and on this basis a map of the angular distribution of local molecular hydrogen at intermediate latitudes is presented. Comparing this with a simular map produced from galaxy counts, several structures appear in both maps in regions related to Gould's Belt and elsewhere. Some regions in the Southern celestial hemisphere not accessible in galaxy counts show high molecular hydrogen column densities.Proceedings of the XVIII General Assembly of the IAU: Galactic Astrophysics and Gamma-Ray Astronomy, held at Patras, Greece, 19 August 1982.