The interstellar radiation field and the production of inverse-Compton gamma rays in the Galaxy

An empirical model for the large-scale galactic distribution of the various components of the interstellar radiation field is constructed using recent observations, and the spectral and spatial distribution of inverse Compton (IC) gamma ray production in the Galaxy is determined using the most recent estimate of the interstellar electron spectrum given by Webber (1983). The integrals involved in the computation of the IC source function are exactly evaluated, and the energy densities of the interstellar radiation field are determined. These computational results are combined to compute the IC volume emissivities at various locations in the Galaxy, and the results are compared with previous estimates and with high-energy gamma-ray observations. It is concluded that, contrary to recent publications, the contribution of IC gamma rays to the observed gamma-ray intensities is negligible compared to the cosmic ray-matter interactions down to at least 10 MeV.