The large-scale diffuse x-ray emission surrounding quasars: an investigation using the scaling-index method

The large-scale (similar to 20') diffuse x-ray background surrounding a sam ple of quasars observed during ROSAT PSPC pointed observations is studied u sing a new source-detection algorithm, the scaling-index method. This algor ithm, which can identify individual photons as belonging to a source or bac kground, is useful for detecting faint, extended sources in noisy fields. U sing this method, we find that, contrary to conclusions drawn by others, th ere is scant evidence for preferential enhancement of x-ray backgrounds sur rounding radio-loud quasars by foreground x-ray emitting clusters of galaxi es. Rather, all fluctuations in these backgrounds can be explained by varyi ng levels of emission from a galactic thermal plasma of temperature T appro ximate to 0.14 keV. No difference is observed between the diffuse x-ray bac kgrounds of radio-loud and radio-quiet quasars.