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Session 12 - Radio Galaxies, VLBI.
Display session, Monday, January 15
North Banquet Hall, Convention Center
A well known and puzzling property of samples of core dominated radio sources, such as as those of the Pearson-Readhead and Caltech-Jodrell surveys, is the bimodal distribution of the apparent misalignment angles between VLBI and VLA scale jets, with peaks at 0\deg and 90\deg. Conway amp; Murphy have proposed a saturating helix geometry to explain the peak at 90\deg. Two sources in which the bend occurs on milliarcsecond scales are 3C\,309.1 (1458\,+\,718) and Markarian 501 (1652\,+\,398).
We present very high dynamic range images of the total intensity and linear polarization structures of both sources at \lambda 6 cm obtained from full syntheses using the complete VLBA. These images reveal the magnetic field structure and a wealth of detail not seen in previous images. The fractional polarization is very high at the main bends (30-60%) and the magnetic field is accurately aligned with the local jet direction.
Both sources show signs of strong interactions with the ambient medium. In Markarian 501 we find two additional sharp bends in the inner jet that have not been seen previously. In 3C\,309.1 the inner jet presently appears to be completely disrupted at a strong shock, forming a ``hotspot'' and a diffuse radio lobe. Neither source appears to lend strong support the Conway - Murphy model, at least in its orginal form.
