Gamma rays and cosmic ray gradiants

The advent of data from the Gamma Ray Observatory, of much higher precision than hitherto, will open up the possibility of deriving more precise results on the presence of ‘cosmic ray gradients’ in the Galaxy. There will still be a variety of difficulties, however. There are still uncertainties in the mass of gas in each of its major forms, HI, H₂ and HII, and their corresponding spatial distribution and the photon field in the Galaxy are known imprecisely. The problem of the contribution to the gamma ray flux from unresolved discrete sources will still be present, too, albeit at a lower level than previously. The division of parent particles between electrons and protons (nuclei) will also continue to be rather uncertain.

These problems are examined in the paper.