The contribution of quasi-stellar objects to the cosmic X-ray background

Abstract

Two methods of estimating the X-ray background which rely less on the yet uncertain theoretical models of luminosity or density evolution, etc., and more on observational estimates are presented. Calculations are performed which show that even if QSOs are local, their net contribution to the X-ray background is less than half. The two methods are: estimation of the X-ray background based on the optical night sky background due to galaxies, and direct estimate of the contribution to the X-ray background from QSOs in the immediate neighborhood.