An Unusual Radio Galaxy in Abell 428: A Large, Powerful FR I Source in a Disk‐dominated Host

Abstract

We report the discovery of a powerful (~1024 h−275 WHz−1 at 20 cm) FR I radio source in a highly flattened disk-dominated galaxy. Half the radio flux from this source is concentrated within the host galaxy, with the remainder in a pair of nearly symmetrical lobes of total extent ~200 kpc nearly perpendicular to the disk. Traditional wisdom maintains that powerful, extended radio sources are found only in ellipticals or recent merger events. We report B, R, J, and K imaging, optical spectroscopy, a rotation curve, an IRAS detection, and a VLA 20 cm image for this galaxy, 0313-192. The optical and near-infrared images clearly show a disk. We detect apparent spiral arms in a deep B-band exposure, and a dust lane from a higher resolution B-band image. The reddened nucleus is consistent with extinction by a similar dust lane. The optical spectrum suggests a central AGN and shows some evidence of a starburst, with both the AGN and central starlight appearing substantially reddened (perhaps by the optical dust lane). From analysis of the extended line emission in [O III] and Hα, we derive a rotation curve consistent with an early-type, dusty spiral seen edge-on. From the IRAS detection at 60 and 100 μm, we find that the ratio of far-infrared to radio flux places this object firmly as a radio galaxy (i.e., the radio emission is not powered by star formation). The radio structure suggests that the radio source in this galaxy is related to the same physical mechanisms that are present in jet-fed powerful radio sources, and that such powerful, extended sources can (albeit extremely rarely) occur in a disk-dominated host.