Lister, Matthew

Parsec-Scale Polarization and Magnetic Field Characteristics of MOJAVE AGN Jets.

Since 2002, the MOJAVE program has gathered multi-epoch full VLBA polarization data at 15 GHz on over 300 compact radio jets associated with AGN. Multi-frequency VLBA polarization data (8.1, 8.3, 12, 15 GHz) were also obtained on 191 of these jets in 2006. With this extensive dataset we have examined parsec-scale Faraday rotation, rotation measure gradients, and core shifts in bright blazars. We detected significant transverse rotation measure gradients in four jets, and find statistical differences in the rotation measures, polarization orientations, and magnetic fields of BL Lac jets as compared to quasars. The weak-lined jets tend to have smaller rotation measures, higher fractional jet polarization, electric polarization vectors better aligned with the local jet direction, and weaker magnetic fields in the VLBI core region. We present preliminary results regarding the time evolution of polarization structures within the jets, and their overall connection with kinematic properties of the flow. We also discuss the polarization properties of gamma-ray bright blazars, which appear to correlate strongly with the location of the synchrotron peak in the overall spectral energy energy distribution.