2004ApJ...600..626S

The z=1.786 radio galaxy 3C 294 lies < 10" from a 12 mag star and has been the target of at least three previous investigations using adaptive optics (AO) imaging. A major problem in interpreting these results is the uncertainty in the precise alignment of the radio structure with the H- or K-band AO imaging. Here we report observations of the position of the AO guide star with the Hubble Space Telescope Fine Guidance Sensor, which, together with positions from the second United States Naval Observatory's CCD Astrograph Catalog (UCAC2), allow us to register the infrared and radio frames to an accuracy of better than 0".1. The result is that the nuclear compact radio source is not coincident with the brightest discrete object in the AO image, an essentially unresolved source on the eastern side of the light distribution, as Quirrenbach and coworkers had suggested. Instead, the radio source is centered about 0".9 to the west of this object, on one of the two apparently real peaks in a region of diffuse emission. Nevertheless, the conclusion of Quirrenbach and coworkers that 3C 294 involves an ongoing merger appears to be correct: analysis of a recent deep Chandra image of 3C 294 obtained from the archive shows that the nucleus comprises two X-ray sources, which are coincident with the radio nucleus and the eastern stellar object. The X-ray/optical flux ratio of the latter makes it extremely unlikely that it is a foreground Galactic star.