The Spiral Host Galaxy of the Double Radio Source 0313?1921

We present new Hubble, Gemini-S, and Chandra observations of the radio galaxy0313-192, which hosts a 350-kpc double source and jets, even though previousdata have suggested that it is a spiral galaxy. We measure the bulge scale andluminosity, radial and vertical profiles of disk starlight, and consider thedistributions of H II regions and absorbing dust. In each case, the HST dataconfirm its classification as an edge-on spiral galaxy, the only such systemknown to produce such an extended radio source of this kind. The Gemini near-IRimages and Chandra spectral fit reveal a strongly obscured central AGN, seenthrough the entire ISM path length of the disk and showing X-ray evidence ofadditional absorption from warm or dense material close to the central object.We consider several possible mechanisms for producing such a rare combinationof AGN and host properties, some combination of which may be at work. Theseinclude an unusually luminous bulge (suggesting a black hole of mass 0.5-0.9billion solar masses), orientation of the jets near the pole of the gas-richdisk, and some evidence of a weak gravitational interaction which has warpedthe disk and could have enhanced fuelling of the central engine. An X-raycounterpart of the kiloparsec-scale radio jet emerges to the south;jet/counterjet limits in both radio and X-ray allow them to be symmetric ifseen more than 15 degrees from the plane of the sky, still consistent with thejet axes being within ~30 degrees of the poles of the gas-rich galaxy disk. Alinear or disklike emission-line structure is seen around thenucleus, inclinedby ~20 degrees to the stellar disk but nearly perpendicular to the jets; thismay represent the aftermath of a galaxy encounter, where gas is photoionized bythe nuclear continuum.Comment: In press, Astron. J. 9 figures; 8 in shrunk JPEG form. Supported by NASA through STScI grant HST-GO-09376.01 and Chandra grant GO4-5118