Comment on Inverse Compton Models for the Isotropic X-Ray Back-Ground and Possible Thermal Emission from a Hot Intergalactic Gas

We have calculated the spectrum of the isotropic X-ray background under the assumption that it arises through Compton scattering of the universal microwave photons by relativistic electrons leaking out of the galaxies. The elegant fit to the experimental data obtained by earlier authors who made many approximations in their calculations disappears in the more detailed treatment presented here. Inverse Compton models for the origin of background X-rays are therefore not adequate to explain all the spectral features in detail. In particular, there is evidence for a thermal component in the X-ray background arising possibly from a hot intergalactic gas at 3 x 1O K.