Flow patterns in radio hot spots: A study of 3C 33 north

High-resolution (0″.36, 0.41 kpc) observations of the northern hot spot of the radio galaxy 3C 33 show a symmetric "mushroom cap" structure, with a centrally placed H-shaped feature and two opposed small bright regions. We explore two models for the flow patterns in this hot spot. First is the "splash" picture, in which the brightest compact feature is identified as the primary hot spot and the rest of the structures result from the jet's expanded, deflected flow. Although most observed features are consistent with this picture, they do not help discriminate against alternative models. The second, axisymmetric, picture compares the observations with numerical simulations of jets with helical magnetic fields. We find good agreement with the geometrical and magnetic field properties, although significant questions remain about the synchrotron emissivity characteristics. We briefly discuss the differences between the northern and southern hot spots of 3C 33, and we suggest that there are no good explanations for these differences in the context of current models. Since the maps of 3C 33's hot spots are among the most detailed available, they demonstrate that other claims about observed flow patterns must be critically examined.