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M. Matuszewski, R.D. Blandford (California Institute of Technology)
We discuss the contribution of intergalactic shock front ion emissions to the cosmic \gamma-ray background in the range 1 to 104 MeV and compare with the data from COMPTEL and EGRET on the GRO. Our approach concentrates predominantly on \pi0 production in cosmic ray proton collisions with the ambient gas in the intergalactic medium (IGM) and their subsequent photo-decay. The computations include effects of increased IGM density around shocks, weak secondary shocks and cosmological expansion. We consider the possibility that the \gamma-ray spectrum feature at around 70 MeV might be due to \pi0arrow\gamma\gamma decay. We compare the ion contribution to the \gamma-ray background to that of inverse Compton scattering of shock accelerated electrons off the cosmic microwave background(CMB).