Collimation and polarization of the jets in 3C 219

Authors:            BRIDLE, A. H.;  PERLEY, R. A.;  HENRIKSEN, R. N.
Affiliation:        AA(National Radio Astronomy Observatory,
                    Charlottesville, VA) AB(National Radio Astronomy
                    Observatory, Socorro, NM) AC(Queen's University,
                    Kingston, Canada)
Journal:            Astronomical Journal (ISSN 0004-6256), vol. 92,
                    Sept. 1986, p. 534-545.


New 4885 MHz VLA maps of the powerful radio galaxy 3C219 show that the transverse width of its brighter radio jet does not grow significantly between 13 and 35 kpc from its nucleus. An elongated radio knot that is probably part of a counter-jet has been radio knot that is probably part of a counter-jet has been discovered. The apparent magnetic field structure of the brighter jet has been mapped at higher resolution than before. The field is well organized, and its mean apparent direction is near the major axis of elongation of the jet over most of the jet's length. Some deviations from this mean direction are systematic, and the largest deviations occur at regular intervals along the jet.

The spreading (i.e., lateral expansion) rate of the jet cannot have been constant with distance from the core. If the spreading rate of the synchrotron emission reflects that of an underlying flow, the flow cannot be freely expanding. It is unlikely that the jet is thermally confined by hot gas that is bound to 3C219 alone, but it may be thermally confined by gas that is bound to the surrounding cluster of galaxies. The radio polarization data neither support nor deny the alternative possibility of magnetically-assisted collimation. We suggest further observations to test both alternatives.

Some of the asymmetries in brightness and geometry between the main jet and the counter-jet in 3C219 can be accounted for if the jets are symmetric, but contain relativistically moving shocks. Such descriptions of the source are not obligatory, however. In particular, episodic models for the energy transport in 3C219 can account for some of the source's features, whether or not the jet velocities are relativistic.

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