Observations of the Soft X-Ray Background

Abstract

Observations of the diffuse X-ray background over a hemisphere of the sky in the galactic anticenter direction provide clear evidence for an excess intensity below 1 keV in all directions. The correlation of this low-energy flux with galactic latitude and with hydrogen column density implies that the radiation originates partially within and partially outside the absorbing layers of the Galaxy. The data are consistent with a model combining an isotropic extragalactic flux with a component due to emitters distributed in the same way as the galactic hydrogen. The mean absorption coefficient of the interstellar medium for photons near 0.28 keV agrees with the theoretically expected value for a uniform absorbing medium and a normal Heill abundance ratio. If discrete sources are responsible for the intensity observed near the galactic plane, then a high density of low4uminosity objects is consistent with our data.