Parsec-scale jet polarization properties of a complete sample of active galactic nuclei at 43 GHz

We present results from the highest resolution polarization imaging survey of a complete sample of extragalactic radio sources carried out to date. Ou r sample consists of a statistically complete flat-spectrum subset of 32 ac tive galactic nuclei (AGNs) from the Pearson-Readhead survey, which has bee n studied at a variety of wavelengths and resolutions, including space-VLBI . Our observations were made with the VLBA at 43 GHz, at which the relative ly higher resolution and weaker opacity effects have allowed us to probe ma gnetic field structures in the jets of these AGNs much closer to the centra l engine than in previous studies. At 43 GHz, the bulk of the total intensi ty and polarized emission in most flat-spectrum AGNs originates from an unr esolved core component located at the extreme end of a faint jet. The lumin osity of the core is positively correlated with the total source luminosity in soft X-rays, in the optical, and at 5 GHz. The most strongly polarized cores display electric vectors that are preferentially aligned with the jet axis, which is consistent with a strong transverse shock that enhances the perpendicular component of the jet magnetic field. Sources with highly pol arized cores also tend to have high optical polarizations and flatter overa ll radio spectra. Approximately half of the AGNs in our sample display appa rently bent jet morphologies that are suggestive of streaming motions along a helical path. The straightest jets in the sample tend to display slower superluminal speeds than those that are significantly bent. Our observation s also show that intrinsic differences in the jet magnetic field properties of BL Lac objects and quasars previously seen on scales of tens of milliar cseconds are also present in regions much closer to the base of the jet.