SIMBAD references

We report the detection of extended X-ray emission around several powerful 3CR quasars with redshifts out to 0.73. The ROSAT HRI images of the quasars have been corrected for spacecraft wobble and compared with an empirical point-spread function. All the quasars examined show excess emission at radii of 15arcsec and more, the evidence being strong for the more distant objects and weak only for the two nearest ones, which are known from other wavelengths not to lie in strongly clustered environments. The spatial profile of the extended component is consistent with thermal emission from the intracluster medium of moderately rich host clusters to the quasars. The total luminosities of the clusters are in the range ∼4x10⁴⁴-3x10⁴⁵erg.s^–1, assuming a temperature of 4keV. The inner regions of the intracluster medium are, in all cases, dense enough to be part of a cooling flow.