The radio morphology of blazars and relationships to optical polarization and to normal radio galaxies

High dynamic range VLA maps of 16 BL Lac objects and highly polarized quasars are presented. Three of the sources are dominated by extended structure with a fairly well-defined orientation. The remaining sources are dominated by an unresolved component coincident with the optical nucleus. Weak evidence is found for a connection between preferred position angles of optical polarization and radio morphology, while a much stronger correlation is found between the prominence of the radio core and the rms scatter in the position angle of the optical polarization. These effects are precisely what is expected in the relativistic jet model. There is remarkably good agreement between the position angle of the small-scale radio structure and the characteristic angle of optical polarization. The result is statistically significant and implies that, at least in some highly polarized objects, the magnetic field of the central optical-emitting region is related to the collimation direction of the radio jet.