Mark R. Swain¹ and Alan H. Bridle
National Radio Astronomy Observatory²,
520 Edgemont Road, Charlottesville, VA 22903-2475
Stefi A. Baum
Space Telescope Science Institute,
2700 San Martin Drive, Baltimore, MD 21218
¹ now at: Astronomy Department, Cornell University,
Ithaca, NY 14850
² The NRAO is a facility of the National Science Foundation, operated under co-operative agreement by Associated Universities, Inc.
We have imaged the total and polarized intensity structures of the jets in the FRII radio galaxy 3C353 with transverse resolutions up to nine beamwidths using the VLA at 8.4 GHz. Both the polarized intensity and the apparent degree of linear polarization exhibit elongated minima near both edges of both jets. We interpret these minima as the result of vector cancellation along the line of sight between polarized emission from the outer layers of the jets and from the surrounding lobes. Both jets also exhibit flat-topped total intensity profiles over much of their length.
We infer that most of the jet emission comes from a thick outer layer where the magnetic field has no component transverse to the jet axis, but the axial and toroidal components are random and approximately in equipartition. We suggest that this region is a boundary layer where the field is ordered by velocity shear. The apparently lower emissivity near the jet axis may be produced by Doppler hiding of emission from fast-flowing material in the jet "spines''. This view of the internal structure of an FRII jet can readily be unified with the two-component model for decelerating FRI jets proposed by Laing (1993, 1996).
galaxies:jets -- radio continuum: galaxies -- magnetic fields -- polarization