The inverse Compton contribution to medium-latitude Galactic gamma-ray emission

We present evidence that the inverse Compton contribution to the diffuse gamma-ray emission above 50 MeV is more important than previously thought. In this paper we compute the spectrum of the excess γ-ray emission above the π0 and bremsstrahlung components. The calculation shows that the excess emission is substantial, amounting to about 60% of the total emission at intermediate latitudes. In the Galactic plane, from which most of the Galactic γ-rays are derived, the excess is relatively much smaller. A model in which there is a cosmic-ray halo of total width 10 kpc and radius 20 kpc yields an inverse Compton contribution which accounts for most of the excess. (author)