S. Jorstad / Boston U., USAS. Jorstad / Boston U., USAA. Marscher / Boston U., USAA. Marscher / Boston U., USAJ. Stevens / Royal Observatory, Edinburgh, UKJ. Stevens / Royal Observatory, Edinburgh, UKA. Stirling / Royal Observatory, Edinburgh, UKA. Stirling / Royal Observatory, Edinburgh, UKM. Lister / Purdue U., USAM. Lister / Purdue U., USAP. Smith / Steward Obs., U. of Arizona, USAP. Smith / Steward Obs., U. of Arizona, USAT. Cawthorne / U. Central Lancashire, UKT. Cawthorne / U. Central Lancashire, UKJ.L. GJ.L. Gómez / IAA, Granada, Spainómez / IAA, Granada, SpainD. Gabuzda / U. College Cork, IrelandD. Gabuzda / U. College Cork, IrelandW. Gear / Cardiff U., UKW. Gear / Cardiff U., UK I. Robson / I. Robson / Royal Observatory, Edinburgh, UKRoyal Observatory, Edinburgh, UK

Multi-Frequency Polarization Properties of BlazarsMulti-Frequency Polarization Properties of Blazars

The SampleThe Sample

Quasars BL Lac Objects Radio galaxies PKS 0420-014 3C 66A 3C 111 PKS 0528+134 OJ 287 3C 120 3C 273 1803+784 3C 279 1823+568 PKS 1510-089 BL Lac 3C 345 CTA 102 3C 454.3

Instruments and Wavelengths Instruments and Wavelengths

VLBA (7 mm ) March 1998 - April 2001 17 epochsBIMA (3 mm) April 2000 - April 2001 3-4 epochsJCMT (0.85/1.3 mm) March 1998 - April 2001 6-11 epochs1.5m Steward Obs. (~6500 Å) Feb. 1999 - April 2005 4-5 epochs

Imaging Imaging Imaging Imaging

www.bu.edu/blazars/multi.html

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 thejets. 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 ComponentsApparent Speed of Jet ComponentsApparent Speed of Jet ComponentsApparent Speed of Jet Components

We determine the apparent speeds, app, for 109 knots.Superluminal apparentspeeds occur in 82% ofthe knots.Statistically significantdeviation from ballistic motion is observed in22% of superluminal knots.

Light Curves of Jet Components Light Curves of Jet Components Light Curves of Jet Components Light Curves of Jet Components

Time Scale of VariabilityBurbidge, Jones, & O’Dell1974, ApJ , 193, 43tvar = dt/ln(Smax/Smin)

Variability Doppler Factorvar = aD/[c tvar (1+z)]D - luminosity distancea - VLBI size of componentc - speed of lightz - redshift

Smax

Smin

dt

Lorentz Factor and Viewing Angle of JetsLorentz Factor and Viewing Angle of JetsLorentz Factor and Viewing Angle of JetsLorentz Factor and Viewing Angle of Jets

The Lorentz factors of the jet flows in the quasars and BL Lac objects rangefrom ~ 5 to >30; the radio galaxies have lower Lorentz factors and widerviewing angles than the blazars (Jorstad et al. 2005, submitted to AJ).

Group I (“BLLac-like”):Group I (“BLLac-like”): 3C 66A, 3C 279, 3C 345, 1803+784, 1823+568, 3C 66A, 3C 279, 3C 345, 1803+784, 1823+568,and BL Lac); the EVPA and BL Lac); the EVPA at most epochsat most epochs is roughly parallel to the jet axis at different is roughly parallel to the jet axis at different

frequenciesfrequencies

1823+568 1823+568

Group II (“Quasar-like”):Group II (“Quasar-like”): 0420-014, 0528+134, OJ 287, 1510-089, CTA102, and 0420-014, 0528+134, OJ 287, 1510-089, CTA102, and 3C454.3; EVPA in the VLBI core is variable but at many epochs 43 GHz core, 230 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.GHz, and optical electric vector position angle correspond to each other.

0528+134 0528+134

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

component. component.

Connection between maximum fractional polarization Connection between maximum fractional polarization at 7mm (core), 1mm, and in the optical regionat 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 IGroup IIGroup III

Connection between minimum fractional polarization Connection between minimum fractional polarization at 7mm (core), 1mm, and in the optical regionat 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 IGroup IIGroup III

Difference between EVPA during high and low polarization Difference between EVPA during high and low polarization statesstates

Group II objects show significantscatter between EVPAs during thehigh and low polarization states, while Group I objects have onlya small difference in polarization direction (within 20o) between the states.

Group IGroup IIGroup III

Connection between polarization level and Connection between polarization level and disturbances in the jet flow disturbances in the jet flow

Conclusions1. 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 increasesin the fractional polarization of the VLBI core, sub-mm and optical polarizationand 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 polarizedemission 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 thetoroidal magnetic field B/Bll >Γ (Lyutikov et al. 2005).