  We investigate the structure of the kpc-scale jet in the nearby (z = 0.073)
radio galaxy 3C 15, using new optical Hubble Space Telescope (HST) ACS/F606W
polarimetry together with archival multi-band HST imaging, Chandra X-ray data
and 8.4 GHz VLA radio polarimetry. The new data confirm that synchrotron
radiation dominates in the optical. With matched beams, the jet is generally
narrower in the optical than in the radio, suggesting a stratified flow. We
examine a simple two-component model comprising a highly relativistic spine and
lower-velocity sheath. This configuration is broadly consistent with
polarization angle differences seen in the optical and radio data. The base of
the jet is relatively brighter in the ultraviolet and X-ray than at lower
energies, and the radio and optical polarization angles vary significantly as
the jet brightens downstream. Further out, the X-ray intensity rises again and
the apparent magnetic field becomes simpler, indicating a strong shock.
Modelling the synchrotron spectrum of this brightest X-ray knot provides an
estimate of its minimum internal pressure, and a comparison with the thermal
pressure from X-ray emitting gas shows that the knot is overpressured and
likely to be a temporary, expanding feature.
