A deep Chandra observation of the cluster environment of the z=1.786 radio galaxy 3C294

Abstract

We report the results from a 200 ks Chandra observation of the z=1.786 radio galaxy 3C294 and its cluster environment, increasing by tenfold our earlier observation. The diffuse emission, extending about 100 kpc around the nucleus, has a roughly hourglass shape in the N-S direction with surprisingly sharp edges to the N and S. The spectrum of the diffuse emission is well fitted by either a thermal model of temperature 3.5 keV and abundance <0.9 solar (2-sigma), or a power-law with photon index 2.3. If the emission is due to hot gas then the sharp edges mean that it is probably not in hydrostatic equilibrium. Much of the emission is plausibly due to inverse Compton scattering of the Cosmic Microwave Background (CMB) by nonthermal electrons produced earlier by the radio source. The required relativistic electrons would be of much lower energy and older than those responsible for the present radio lobes. This could account for the lack of detailed spatial correspondence between the X-rays and the radio emission, the axis of which is at a position angle of about 45 deg. Hot gas would still be required to confine the relativistic plasma; the situation could parallel that of the radio bubbles seen as holes in nearby clusters, except that in 3C294 the bubbles are bright in X-rays owing to the extreme power in the source and the sixty fold increase in the energy density of the CMB. The X-ray spectrum of the radio nucleus is hard, showing a reflection spectrum and iron line. The source is therefore an obscured radio-loud quasar.