Nature of the extended emission features in IRAS 04210+0400

The IRAS source 04210+0400 coincides with a galaxy that exhibits strong double-lobed radio emission extending 15 kpc outside the optical galaxy. New high-resolution radio maps reveal a classical low-luminosity double radio structure and an extended nuclear source that is aligned toward a hot spot in one of the lobes. Visible spectroscopy shows that the light from the features that were originally thought to be spiral arms is neither starlight nor light scattered from the nucleus; the spectra show strong emission lines whose relative intensity, radial velocity, and velocity dispersions vary with position. The data suggest that the extended spiral features are photoionized remnants of earlier radio jet activity and that the unusual properties of this object might be characterized as those of a radio galaxy that has an unusually high dust content and a strong source of ultraviolet radiation at its core. The nuclear activity may be related to an interaction with a nearby companion galaxy. 19 references