Correlation of gamma-ray fluxes with southern hemisphere CO data.
Manchester, R. N.; Wolfendale, A. W.; Whiteoak, J. B.; Riley, P. A.; Xu, C. -X.; Robinson, B. J.
United Kingdom, Australia
Abstract
A new radio survey of the C-12O molecule in the Galactic plane covering the longitude range l:294 - 358 deg is compared with the flux of high energy gamma rays in the same region. A good correlation between the two is found, and it is shown that the data are consistent with the hypothesis that most of the gamma-ray flux is produced by the cosmic-ray irradiation of interstellar gas. The gamma-ray emissivity of atomic hydrogen is derived and found to be consistent with that determined by other workers at higher latitudes. It is shown that the apparent emissivity of molecular hydrogen has a different energy dependence from the atomic gas, and some reasons for this are discussed. Three of the four gamma-ray sources listed in the COS-B 2CG catalog in the longitude range in question are found to be well correlated with peaks in the CO distribution thereby suggesting that they too may be due to cosmic-ray interactions with the clumpy gas.