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W.C. Keel (U. Ala.), M.J. Ledlow (Gemini Obs.), F.N. Owen (NRAO)
Powerful double radio sources universally arise from elliptical galaxies or merger remnants, which has shaped theories of their origin. Thus, it was important to confirm the nature of the disk galaxy identified with the 200-kpc FR I source 0313-192 at z=0.067. HST ACS and Gemini-S JHK images show clearly that this is indeed a spiral galaxy, seen within 0.5\circ of edge-on. The dust lane is thick, highly structured, and warped by 3\circ to the starlight midplane. The stellar disk is thick and red, with z scale height nearly 1/4 of the radial scale length. H II regions are visible in the disk plane where the warp or gaps allow us to see them around the dust. Star formation, radial extent of the dust, and modest bulge/disk ratio all indicate that the galaxy is a genuine spiral, the only one identified to host a giant double radio source. H\alpha and [O III] emission trace a nuclear structure spanning ~5 kpc, tilted by ~30\circ to the disk and perpendicular to the inner radio jet, which is more like an inner disk than ionization cones. The optical depth from dust (as well as H I) is comparable to that in our own disk. Reddened nuclear light becomes prominent at K, at a location matching both the radio core and the center of the bulge isophotes. Several of these features may be remnants of a minor merger in this unusually luminous spiral, which might give clues to how such an unusual host can support a large and powerful double radio source. A luminous bulge, dynamical perturbation, and jet axis nearly perpendicular to the disk might all be implicated in allowing the ``wrong" kind of host galaxy to show this powerful activity. This work was supported by NASA under grant GO-09376.01A from STScI.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.