Constraints on a dense hot intergalactic medium

We propose a model in which exploding galaxies heat the intergalactic gas (IGG) to 10/sup 8/--10/sup 9/ K. The thermal bremsstrahlung from the model agrees with spectral measurements of the X-ray background (XRB). We show that recent submillimeter measurements of the cosmic microwave background (CMB) are consistent with a spectrum distorted from blackbody by Compton scattering on the same IGG. We also show that the isotropy and intensity of the XRB rule out its origin from discrete gas clouds. Because of the large energy requirement of heat the IGG and other considerations, we must regard the existence of a cosmologically significant amount of hot IGG as uncertain. We conclude that the amount of hot IGG is ..cap omega../sub I/9 or approx. =1.0.