High- resolution VLBA Observations of Low- Luminosity Radio Galaxies

There is a well-known dichotomy of radio galaxies: low- luminosity ``FR I'' objects have edge-darkened structures with twin kiloparsec-scale jets, while high-luminosity ``FR II'' sources have edge-brightened structures with one-sided kiloparsec-scale jets. The ``magnetic switch'' model of Meier et al. (1997, Nature, 388, 350) predicts that parsec-scale jet speeds will be slower (0.6c) in ``FR I'' objects and faster ($>$0.98c) in ``FR II'' sources. To test this model, we made high-resolution 8.4-GHz VLBA observations of the ``FR I'' radio galaxies 3C31, 3C76.1, 3C296, and 3C449 on 2003 August 13. All four objects have compact cores. 3C31 and 3C296 show well- resolved jet structures on the scale of about 1 pc, with possible counterjet features. Analyses of the current images suggest that the jets lie at large angles (75-80 degrees) to our line of sight, but do not provide strong constraints on jet speeds. Future observations are planned for direct measurements of jet speeds.