Origin of the X-ray background

Abstract

Energetic electrons produced by an early generation of supernovae could have given rise to the diffuse X-ray and ..gamma..-ray background by inverse Compton scattering on ambient photons emitted by the supernova population. If the supernovae were formed at epochs 3 x 10/sup 7/approximately-less-thantapproximately-less-than10/sup 8/ years (20approximately-less-thanzapproximately-less-than50) and if the spectrum of the electrons they injected into the (then) interstellar medium resembled the present-day spectrum of primary Galactic cosmic-ray electrons, then the predicted X- and ..gamma..-ray spectrum closely resembles the observed spectrum over an energy range of five decades. In particular, the present theory predicts the observed change in spectral index around 25 keV.The properties of the supernova population needed to secure quantitative agreement between the predictions of the present theory and observation are identical with those postulated earlier by Layzer and Hively to explain the microwave background.