Origin of the Structures and Polarization in the Classical Double 3C 219

Scaled-array VLA observations of the "classical double" radio galaxy 3C 219 at 1.4, 1.5, 1.7, and 4.9 GHz with 1.4" resolution have been used to derive the spectral and polarimetric properties of the source. The extended emission of the lobes is filamentary, as in other well-resolved radio galaxies. A second type of filamentation, spatially independent of the total intensity filaments, is found in the depolarization distribution of the source. The depolarization filaments are associated with strong local gradients in the rotation measure and may indicate that a clumpy magnetoionic medium surrounds the radio galaxy. 3C 219 is one of the few Fanaroff-Riley Class II radio sources known in which there is direct evidence for a counterjet. Both the counterjet and main jet are "partial jets," i.e., they seem to disappear long before reaching the hot spot in their associated lobes. The disappearance of the main jet is accompanied by a transition from an axial to a transverse magnetic field along the jet axis. Two interpretations for the abbreviated nature of the jets are considered. The "born-again, relativistic jet" model assumes an episodic behavior in the relativistic outflow from the radio core. The "passive magnetic field" model relates the observed asymmetries between the two jets to different orientations of the passive magnetic field that they transport. The strengths and weaknesses of each model as applied to 3C 219 are discussed. Finally, the observations are compared with numerical simulations of propagating jets with both active (dynamically important) and passive (dynamically negligible) magnetic fields.