A Large‐Scale Jet and FR I Radio Source in a Spiral Galaxy: The Host Properties and External Environment

We have identified a large (~200 kpc), powerful double radio source whosehost galaxy is clearly a disk and most likely a spiral. This FR I radio galaxyis located very near the center of the RC 0 cluster Abell 428. The existence ofsuch an object violates a fundamental paradigm for radio loud AGN. In paper I,we showed that this object was most likely a spiral host with optical lineratios and colors consistent with an AGN. In this paper, we present new, higherresolution radio imaging, a radio/mm continuum spectrum for the nucleus, adetection of HI absorption against the bright radio core, an upper-limit to COand the gas mass, and 70 optical redshifts. We confirm the existence of a radiojet at 20cm extending 42 kpc into the southern lobe. At 3.6cm, we also detect anuclear jet similar in length to that in M87 but 10 times weaker. We believethat this is the first detection of a radio jet on these scales in a disk orspiral host galaxy. The nuclear radio spectrum is similar to many blazar or QSOlike objects, suggesting that the galaxy harbors an imbedded and obscured AGN.We model a turnover in the spectrum at low frequencies as Free-Free absorption.We detect very strong and narrow HI absorption with nearly the entire 20 cmcore continuum absorbed, implying an unusually large optical depth (tau~1). Wesuggest that the nucleus is seen through a disk-like distribution of ISM gas,possibly through a spiral arm or a warp to account for the high column density. From the radial velocities, we find that A428 is in fact made up of at least2 clumps of galaxies separated by 3300 km/s, which are imbedded in a nearlycontinuous distribution of galaxies over 13000 km/s in velocity. Thus, theenvironment resembles a poor group within a filament viewed end-on.Comment: 21 pages, 9 Figures, 2 Tables; to appear in Ap