Millimeter and Submillimeter Polarization Observations of Blazars

Abstract

Millimeter and submillimeter polarization observations of blazars from the James Clerk Maxwell Telescope are presented. The data are interpreted in light of recent results from centimeter wavelength VLBI polarimetry studies. Observations of the superluminal quasar 3C 279 at 1.1 and 0.8 mm give a degree of polarization in excess of 10% and imply that the magnetic field is aligned orthogonal to the milliarcsecond (mas) jet to within 6°. This magnetic field orientation is consistent with that expected to arise in a transverse shock. The high level of polarization suggests that the centimeter VLBI core is depolarized by Faraday rotation rather than by increased magnetic field disorder at the base of the inhomogeneous relativistic jet. Three BL Lacertae objects were observed at 1.1 mm and were found to be between 3% and 17% polarized with position angles either closely parallel or closely perpendicular to the mas jet. Although further observations are needed, these data favor a picture in which the position angles in the cores of BL Lac objects display a bimodal distribution as found by centimeter VLBI studies. The close relationship between the millimeter polarization position angle and the mas jet is surprising given the results of millimeter VLBI studies which show evidence for significant jet bending.