| Abstract : | We will present the preliminary results from our polarimetric observations with the GMRT and EVLA of a sample of radio-loud quasars and BL Lac objects belonging to the Palomar-Green (PG) sample. These `blazar' sub-classes have been suggested to result from either `intrinsic' differences like magnetic field structures in jets, or `extrinsic' differences like the density of their surrounding magneto-ionized medium. Our aim was to look for both intrinsic and extrinsic differences using the technique of radio polarimetry. The PG sample is one of the best-studied AGN samples with accurate black hole mass estimates, accretion rates, emission-line data, and star-formation rates. Our preliminary results using the GMRT and EVLA at multiple radio frequencies indicate tentative differences between intrinsic and extrinsic factors between the radio-loud quasars and BL Lac objects. |
