S. Jorstad / Boston U., USA /St. Petersburg State U., RussiaA. Marscher / Boston U., USAM. Lister / Purdue U., USAA. Stirling / U. of Manchester, Jodrell Bank Obs., UKT. Cawthorne / Central Lancashire U., UKW. Gear / Cardiff U., UK J.L. Gómez / IAA, Granada, Spain J. Stevens / Royal Observatory, UK P. Smith / Steward Observatory, USA J. Foster / U. of California, Berkeley, USA I. Robson / Royal Observatory, UK

Apparent Speed as a Probe of Parsec-Scale Jet in AGN Apparent Speed as a Probe of Parsec-Scale Jet in AGN

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 2001 4-5 epochs

OUTLINEOUTLINE

1. Study of apparent speed distributions in individual sources and in different group of AGNs.

2. Determination of jet parameters: Doppler and Lorentz factors, viewing and opening angles.

3. Searching for acceleration/deceleration in the jets

4. Analysis of the brightness temperature on parsec scales.

Imaging Imaging

www.bu.edu/blazars/multi.html

ModelingModeling

Parameters of ComponentS (mJy) - flux densitySp(mJy) - polarized flux densityR (mas) - distance from the core(deg) - PA relative to the coreEVPA(deg) - electric vector PAa (mas) - size

www.bu.edu/blazars/multi.html

Classification of Component’s Motion Classification of Component’s Motion

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.

Acceleration of the Jet Flow Acceleration of the Jet Flow

The majority of non-ballisticcomponents undergo an increase of apparent speed with distance from the core.This could be the result ofphysical accelerations (Vlahakis & Königl 2004,ApJ, 605, 656) or from selection of sources whose angles to the line ofsight < sin -1(1/) near the core and closer to this valuefarther out.

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

Flux Variability Time Scale vs. Size Variability Time Scale

Flux Variability Time Scale vs. Size Variability Time Scale

The straight line indicatesThe expected relationbetween tvar and ta

for adiabatic losses foroptically thin shock with =0.7 , S-

(Marscher & Gear 1985,ApJ, 298, 114)

Apparent Speed - Doppler Factor Relation Apparent Speed - Doppler Factor Relation

2-cm survey (Kellermann et al. 2004)

Lorentz Factor and Viewing Angle of Jet Components Lorentz Factor and Viewing Angle of Jet Components

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.

Intrinsic Brightness Temperature of Jet Components Intrinsic Brightness Temperature of Jet Components

Tb,obs= 7.5108 Smax/a2 K Tb.int = Tb,obs (1+z)1.7/1.7 K =0.7 S-

Quasars: <Tb.int >=3.5109 KBL Lacs: <Tb.int >=5.5107 KRG: <Tb.int >=1.4109 KComparison of these values with the equipartion brightness temperature of theoptically thick part of the jets,Tb.int >=2-51010 K, implies a faster decrease of Tb with distance down the jet, which suggests a stronger magnetic field in the BL Lac objects (Readhead 1994, ApJ, 426, 51).

Projected Half Opening Angles of Jets Projected Half Opening Angles of Jets

Projected Opening Angle, p

p = tan -1 < strans = slong tan -1 + so> strans = R slong = R sin (|jet- |)+a/2

Intrinsic Half Opening Angles of Jets Intrinsic Half Opening Angles of Jets

1/ (Blandford & Königl 1979,ApJ, 232, 34)Intrinsic Half Opening Angle, = p

sin < o> = / (rad), where = 0.2 ± 0.1 = √(Pext / Po) (Daly & Marscher1988, ApJ, 334, 539) =0.5 Pext / Po = 1/4

Conclusions

1. We have measured the apparent speed of 106 features in the inner jets of 15 AGNs. Superluminal apparent speeds occur in 80% of the knots, 26% of which show statistically significant deviations from ballistic motion. The majority of non-ballistic components undergo an increase of apparent speed with distance from the core.

2. We suggest a new method to define Doppler factor, based on the assumption that the decay in flux of the superluminal components is caused by radiative losses rather than by cooling from expansion, and is subject to light-travel delays.

3. The derived parameters of the jets indicate that in our sample the quasars have the highest Doppler factors and smallest viewing and opening angles, while the two radio galaxies possess significantly lower Doppler factors, larger viewing angles, and wider opening angles despite their `blazar-like'' radio properties.

4. We have estimated the intrinsic brightness temperatures of jet components in the quasars, BL Lacs, and radio galaxies on parsec scales. Comparison of these values with the equipartition brightness temperature of the optically thick part of the jets suggests a stronger magnetic field in the BL Lac objects.