Evaluation of Models for Diffuse Continuum Gamma Rays in EGRET Range

The GALPROP model for cosmic-ray (CR) propagation produces explicit predictions for the angular distribution of Galactic diffuse γ-rays. We compare our current models with EGRET spectra for various regions of the sky. This allows a critical test of alternative hypotheses for the observed GeV excess. We show that a population of hard-spectrum γ-ray sources cannot be solely responsible for the excess since it also appears at high latitudes; on the other hand a hard CR electron spectrum model cannot explain the γ-ray excess in the inner Galaxy. Hence some combination of these explanations is suggested.