VLBA Observations of Blazars S. Jorstad / Boston U., USA /St. Petersburg State U., Russia

Spectral Energy Distribution of Blazars Marscher 2008, in press

Very Long Baseline Array (VLBA), National Radio Astronomy Observatory, USA Compact Jets 3pc

Instruments and Wavelengths The 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 VLBA (7 mm ) March 1998 - April 2001 17 epochs BIMA (3 mm) April 2000 - April 2001 3-4 epochs JCMT (0.85/1.3 mm) March 1998 - April 2001 6-11 epochs 1.5m Steward Obs. (~6500 Å) Feb. 1999 - April 2001 4-5 epochs

Collaborations Marscher / Boston U., USA M. Lister / Purdue U., USA A. Stirling / U. of Manchester, Jodrell Bank Obs., UK T. Cawthorne / Central Lancashire U., UK W. Gear / Cardiff U., UK J.L. Gómez / IAA, Granada, Spain J. Stevens / Royal Observatory, UK P. Smith / Steward Observatory, USA J. R. Foster / U. of California, Berkeley, USA I. Robson / Royal Observatory, UK

Motion in Compact Jets

OUTLINE Study of apparent speed distributions in individual sources and in different group of AGNs. Determination of jet parameters: Doppler and Lorentz factors, viewing and opening angles. Analysis of polarization properties at different wavelengths Direction of the magnetic field with respect to the jet direction 5. Where does emission at different wavelengths originate in compact jet?

2cm Apparent Speed 7mm n=57 n=22 n=23 Quasars: app 7mm =(12.75.3 )c Quasars: app 2cm =( 7.3±0.8 )c Kellermann et al. 2004 Quasars: app 6cm =( 2.90.9 )c (186 components) Britzen et al. 2008

Traditional Estimate of Lorentz factor & Viewing Angle of Jet app =  sino (1- coso)-1  ≈ appmax ; o ≈ 1/appmax ;  = (1 - 2)-1/2 = -1(1- coso)-1;  ≈ appmax

Derivation of Lorentz & Doppler factors & Viewing Angle of Jet Method of Jorstad et al. (2005, AJ, 130, 1418)) Variability Doppler Factor var ≈ aD/[c tvar (1+z)] tvar = dt/ln(Smax/Smin) a: angular diameter of component - method requires that light-travel effects determine time scale (works at 43 GHz) = -1(1- coso)-1 app =  sino (1- coso)-1 = (1 - 2)-1/2

Jet Parameters for a Source Although there is a scatter of Lorentz factors and viewing angles derived for a given source from  and app of different superluminal components, the values for a given source are closely grouped

Lorentz Factor and Viewing Angle of Jet Components 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.

Opening Angles of Jets Projected Opening Angle, p p = tan -1  < strans = slong   + so> slong = R strans = R sin (|jet- |)+a/2 slong strans Intrinsic Opening Angle,   1/ (Blandford & Königl 1979, ApJ, 232, 34)  = 2p sin < o>  = / (rad), where  = 0.6 ± 0.1

Dependence of Jet Parameters on Source Type Radio galaxies =4.81.5, o=19o 4o = 6.4o 1o , =2.80.9 Quasars =19.28.6, o=2.6o 1.9o = 1.0o 0.6o , =2311 BL Lac objects =12.85.3, o=4.4o 3.0o = 1.2o 0.8o , =13.56.7

High Variability of Polarization Parameters in the VLBI core Epoch min = 12 days

Intermediate Variability of Polarization Parameters in the VLBI core Epoch min = 56 days

Low Variability of Polarization Parameters in the VLBI core

Polarization Variability Indices in the VLBI Core Va7mm (mmax -max)-(mmin +min ) Vp=____________________________ (mmax -max)+(mmin +min ) mmax  max - maximum observed percentage of polarization mmin  min - minimum observed 0420-01 0528+13 OJ287 1510-08 CTA102 3C454.3 3C66A 3C279 3C345 1803+78 1823+56 BLLac - (12 +22 )1/2 Va=___________________ 90 - observed range of EVPAs 1,2 - the uncertainties in the values of EVPAs that define the range. 3C273 3C111 3C120

Dependence of degree of polarization on wavelengths For a given variability group, the peak of the distribution shifts to higher degree of polarization at shorter mm-. This suggests that the emission region is larger at longer wavelengths. The peak of the distribution has the highest degree of polarization in the IVP group and the lowest degree of polarization in the LVP group, independent of . This suggests that either the emission regions of the LVP and HVP sources are larger than those in the IVP sources or magnetic field in the LVP and HVP sources has finer structure than in the IVP sources.

Correlation of degree of polarization at different wavelengths Lister & Smith 2000 There is a strong correlation between the polarization in the radio core at 7 mm and overall optical polarization in radio-loud AGN.

Faraday rotation in the VLBI core in the HVP and IVP groups EVPA (deg.) 2 (cm2) EVPA (deg.) 2 (cm2)  = 1mm + RM 2 IVP HVP

Faraday Rotation in the LVP group 7mm 3mm 3C273 Polarization, % Epoch Polarization, % Epoch Polarization, % Epoch RM=2.1104 rad m-2 Attridge et al. 2005 RM>5105 rad m-2

Dependence of Faraday Rotation on group LVP IVP RMo> 5  105 rad m-2 RMo= (1.10.3)  104 rad m-2 HVP RMo= (8.56.5)  104 rad m-2

Comparison of EVPAs at different wavelengths The distributions of offsets between polarization position angles at different wavelengths show 1) excellent agreement between polarization position angles in the IVP sources; 2) for the HVP sources the result is qualitatively different, however the best agreement is observed between EVPAs at optical wavelengths and in the 7mm core (64% out of 22 measurements are located within 20 degrees.

Position angle of polarization relative to the Jet Axis The properties of polarization position angle with respect to the jet direction are distinct for each group, independent of wavelength. 1. Intrinsic difference in the structure of the magnetic field - large scale in the IVP - fine structure in the HVP - the finest structure in the LVP 2. Difference in the amount of hot gas in the core region 3. Difference in morphology of the inner jet: - straight symmetric jets in the IVP - curved asymmetric jets in the HVP - wide, with a velocity gradient across the jet, jets in the LVP 4. Difference in shock strengths (Lister & Smith 2000)

Connection between Lorentz factor and Polarization Variability 1mm 7mm In the shock-in-jet model (e.g. Marscher & Gear 1985) polarized regions at different wavelengths are partially co-spacial and have essentially the same Lorentz factor. In this model a correlation between bulk Lorentz factor and polarization variability index is expected if the minimum degree of polarization is corresponding to unshocked plasma and the maximum - to faster, shocked plasma.

Where does polarized emission at different wavelengths originate? Correlation Optic.  1mm 7mm m7mm wrt m 0.87 0.59 opt - <20o 46% 77% Vp wrt  0.53 -0.12 0.72 The findings suggest: 1. Another emission component in addition to shocks is prominent at 1 mm. A primary candidate is the “true” core - bright narrow end of the jet observed at a wavelength where the emission is completely optically thin. 2. The true core does not possess relativistic electrons energetic enough to produce the optical synchrotron emission. 3. The nonthermal optical emission arises in shocks close to the 7mm VLBI core.