Gabriele Giovannini Marcello Giroletti Gregory B. Taylor Dipartimento di Astronomia, Bologna University Istituto di Radioastronomia, INAF Bologna Dept. of Physics and Astronomy, Univ. of New Mexico The jet of Markarian 501 from the sub-parsec to the kpc scale

z = mas = 0.67 pc Tavecchio et al From NED

Mkn 501 –Large Scale VLA 20 kpc Symmetric structure Jets are no more relativistics on 10 kpc scale Koolgaard et al. 1992

1.5 kpc VLA A array at 1.4 GHz At 2 arcsecond  β cosθ > 0.36 At 1 arcsecond  β cosθ > kpc VLA B array (Cassaro et al. 1999)

HPBW = 9x5 mas 35 pc At 100 mas: β cosθ > 0.61 At 50 mas: β cosθ > 0.77

The jet shows a complex and continuous morphology with many sharp bends before undergoing a last turn in the PA of the kpc scale structure. The jet is clearly limb brightened. At 10 mas: β cosθ > pc

Evident limb-brightened structure beginning very near to the core and visible up to 100 mas from it. It is interpreted as evidence of a velocity structure. No proper motion has been found comparing 9 different epochs from to Compact structures are resolved and complex in high resolution images 22 GHz 1.6 GHz VSOP 1.5 pc 3 pc 10 pc 22 GHz

Thanks to the global mm VLBI network: VLBA (7 telescopes), Eb, Plateau de Bure, Pico Veleta, Onsala, Metsahovi A radio core + one sided jet is visible in recent VLBI observations at 86.2 GHz with a linear resolution of 0.08 x 0.13 pc (HPBW) Giroletti et al. in prep.

Core: unresolved at 86 GHz  size lower than 0.03 pc (gaussian fit) 1 R s = pc (M = 10 9 M o ) High frequency spectrum is steep with a turnover at about 8.4 GHz. It implies a magnetic field in the range 0.01 – 0.03 G and that inside the “core” a structure is present We do not have polarization information Gabuzda et al. 2004: B fields are dominated by the toroidal component.

0.08 pc Better images to: find the core position measure the jet dynamics (starting velocity and acceleration + velocity structure)

Jet velocity and orientation from data: High velocity jet with Γ =15 and θ = 4 o (δ  15) in the gamma- ray region (< 0.02 mas < 0.02 pc) – from high frequency emission, gamma-ray variability, and SED (SSC models) In the radio jet region the jet orientation move from 4 o to 10 o - 15 o to explain the limb-brightened structure radio structure and Γ decrease to 10 (δ  2.6) at mas from the core ( pc) The jet velocity decrease is low: from HSA data we estimate relativistic jets (v > 0.6 c at 1” from the core) At 5” (  10 kpc de-projected) the jet is no more relativistic (Γ= 1.02 v = 0.2c) as expected from FR I jet velocities Jet PA not constant for unknown reasons

Observational data are in agreement with a simple adiabatic model if the magnetic field is mostly perpendicular to the jet (a parallel field predicts a too fast velocity decrease with respect to the j cj ratio) Adiabatic model in the case of relativistic motion discussed by Baum et al See also Cotton et al. 1999, and Giroletti et al Jet initial velocity c

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