2001MNRAS.322L..11F

We present a Chandra observation of the powerful radio galaxy 3C 294 showing clear evidence for a surrounding intracluster medium. At a redshift of 1.786 this is the most distant cluster of galaxies yet detected in X-rays. The radio core is detected as a point source, which has a spectrum consistent with a heavily absorbed power law, implying an intrinsic 2-10keV luminosity of ∼10⁴⁵erg.s^–1. A small excess of emission is associated with the southern radio hotspots. The soft, diffuse emission from the intracluster medium is centred on the radio source. It has an hourglass shape in the north-south direction, extending to radii of at least 100 kpc, well beyond the radio source. The X-ray spectrum of this extended component is fitted by a thermal model with temperature ∼5keV, or by gas cooling from above 7keV at rates of ∼400-700M_☉.yr^–1. The rest-frame 0.3-10keV luminosity of the cluster is ∼4.5x10⁴⁴erg.s^–1. The existence of such a cluster is consistent with a low-density universe.