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We have used the ROSAT HRI to observe 2 quasars (PKS 2352-34 and 3C~263) known to reside in clusters of galaxies at z$\sim$0.7 with the intent of detecting X-ray emission from the ICM of the host cluster. Detections of, or interesting upper limits to, quasar host cluster X-ray emission help determine the physical conditions of quasar environments and provide clues to the mechanisms that govern quasar creation and evolution. In addition, quasar host clusters show evidence for being younger than optically- and X-ray-selected clusters of similar richnesses, and so comparison of the properties of these different samples of clusters may provide insight into the evolution of galaxy clusters.
The intrinsic PSF of the ROSAT optics + HRI instrument is well characterized and has FWHM$\sim\!5''$. However, aspect (pointing and guiding) errors can smear images over a considerably larger area, as well as distort them into noncircular shapes. This limits the accuracy of PSF subtraction, resulting in shallower and less interesting detection limits for given exposure time. We are experimenting with several different approaches toward PSF modelling and subtraction in search of the optimal method applicable to our data. We will present our results so far and discuss the prospects for improved detection limits with proposed ROSAT A05 observations of fainter quasars in richer clusters at lower redshift.
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