Confusion of diffuse objects in the X-ray sky

Abstract

Most of the baryons in the present-day universe are thought to reside in intergalactic space at temperatures of 10(5)-10(7) K. X-ray emission from these baryons contributes a modest (similar to 10%) fraction of the similar to1 keV background whose prominence within the large-scale cosmic web depends on the amount of nongravitational energy injected into intergalactic space by supernovae and active galactic nuclei. Here we show that the virialized regions of groups and clusters cover over a third of the sky, creating a source-confusion problem that may hinder X-ray searches for individual intercluster filaments and contaminate observations of distant groups.