S. Jorstad / Boston U., USA A. Marscher / Boston U., USA J. Stevens / Royal Observatory, Edinburgh, UK A. Stirling / Royal Observatory, Edinburgh, UK M. Lister / Purdue U., USA P. Smith / Steward Obs., U. of Arizona, USA T. Cawthorne / U. Central Lancashire, UK J.L. Gómez / IAA, Granada, Spain D. Gabuzda / U. College Cork, Ireland W. Gear / Cardiff U., UK I. Robson / Royal Observatory, Edinburgh, UK I. Robson / Royal Observatory, Edinburgh, UK Multi-Frequency Polarization Properties of Blazars

The Sample Quasars BL Lac Objects Radio galaxies PKS C 66A 3C 111 PKS OJ 287 3C 120 3C C PKS BL Lac 3C 345 CTA 102 3C Instruments and Wavelengths VLBA (7 mm ) March April epochs BIMA (3 mm) April April epochs JCMT (0.85/1.3 mm) March April epochs 1.5m Steward Obs. (~6500 Å) Feb April epochs

ImagingImaging

Goals Of the Project 1. To investigate connection between the polarized mm, sub-mm, and optical emission and structure of the radio jets. 2. To define time scales of variability of the polarization parameters at different frequencies. 3. To search for relation between variability of the polarization parameters and dynamical processes in the jets. 4. To determine parameters of the jets (apparent speed, acceleration/deceleration of the jet flow, viewing and opening angles, ejection rate).

Apparent Speed of Jet Components We determine the apparent speeds,  app, for 109 knots. Superluminal apparent speeds occur in 82% of the knots. Statistically significant deviation from ballistic motion is observed in 22% of superluminal knots.

Light Curves of Jet Components Time Scale of Variability Burbidge, Jones, & O’Dell 1974, ApJ, 193, 43  t var = dt/ln(S max /S min ) Variability Doppler Factor  var = aD/[c  t var (1+z)] D - luminosity distance a - VLBI size of component c - speed of light z - redshift S max S min dt

Lorentz Factor and Viewing Angle of Jets The Lorentz factors of the jet flows in the quasars and BL Lac objects range from  ~ 5 to  >30; the radio galaxies have lower Lorentz factors and wider viewing angles than the blazars (Jorstad et al. 2005, submitted to AJ).

Group I (“BLLac-like”): 3C 66A, 3C 279, 3C 345, , , and BL Lac); the EVPA at most epochs is roughly parallel to the jet axis at different frequencies

Group II (“Quasar-like”): , , OJ 287, , CTA102, and 3C454.3; EVPA in the VLBI core is variable but at many epochs 43 GHz core, 230 GHz, and optical electric vector position angle correspond to each other.

Group III (“unpolarized VLBI core”): 3C 111, 3C 120, and 3C 273; the JCMT polarization is similar to the 43 GHz polarization of a very strong superluminal component.

Connection between maximum fractional polarization at 7mm (core), 1mm, and in the optical region Consider the highest state of polarization for each source: Separation into groups is supported by different values of fractional polarization: 1. Group I objects show the highest polarization at all wavelengths: from 7% to 25 % at 7mm, from 10% to 36% at 1mm, and from 8% to 40% in the optical region. 2. Group II objects possess similar polarization at 7 and 1mm (~ 8%). 3. Objects with unpolarized VLBI core have the lowest level of optical polarization. Group I Group II Group III

Connection between minimum fractional polarization at 7mm (core), 1mm, and in the optical region For the lowest state of polarization of each source: Separation into groups is supported by different values of fractional polarization: 1. Group I objects show the highest polarization at all wavelengths. 2. Group II objects possess similar polarization at 7 and 1mm (~ 1-2%). 3. Objects with unpolarized VLBI core have the lowest level of the polarization at all wavelengths. Group I Group II Group III

Difference between EVPA during high and low polarization states Group II objects show significant scatter between EVPAs during the high and low polarization states, while Group I objects have only a small difference in polarization direction (within 20 o ) between the states. Group I Group II Group III

Connection between polarization level and disturbances in the jet flow

Conclusions 1.Analysis of the data shows an obvious connection between the polarized emission at sub-mm wavelengths and strongest polarized emission in parsec-scale jets of the quasars and BL Lac objects. This implies co-spatiality of the emission region or roughly the same magnetic field direction in the emission regions at both frequencies. 2. The sample demonstrates a significant correlation between fractional polarization in the optical region and level of polarization of the VLBI core (Lister & Smith 2000). 3. For the “quasar –like “ group of sources there is a connection between increases in the fractional polarization of the VLBI core, sub-mm and optical polarization and ejections of new superluminal knots. This suggests that high levels of polarization in these objects result from ordering of the magnetic field by shock formation (Marscher & Gear 1985) which is responsible for the polarized emission at different wavelength. 4. The “BL Lac-like” group of sources contains the highest fractional polarization and most stable direction of polarization along the jet. This is possible to explain for jets with intrinsic toroidal magnetic field ( in the frame of the jet) that is of the order of, or stronger than, the intrinsic poloidal field. In this case, the highly relativistic motion implies that, in the observer’s frame, the jet is strongly dominated by the toroidal magnetic field B  /B ll >Γ (Lyutikov et al. 2005).