Gabriele GiovanniniMarcello GirolettiGregory B. Taylor

Dipartimento di Astronomia, Bologna UniversityIstituto 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 = 0.034 1mas = 0.67 pc

Tavecchio et al. 2001

From NED

Mkn 501 –Large Scale

VLA

20 kpc

Symmetric structureSymmetric structure

Jets are no more relativisticsJets are no more relativistics

on 10 kpc scale on 10 kpc scale

Koolgaard et al. 1992

1.5 kpc1.5 kpc

VLA A array at 1.4 GHz

At 2 arcsecond β cosθ > 0.36

At 1 arcsecond β cosθ > 0.63

1.5 kpc1.5 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 manysharp 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 > 0.92

15 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 1995.29 to 1999.55. Compact structures are resolved and complex in high resolution images

22 GHz

1.6 GHz VSOP

1.5 pc1.5 pc

3 pc3 pc

10 pc10 pc

22 GHz22 GHz

Thanks to the global mm VLBI network:VLBA (7 telescopes), Eb, Plateau de Bure,Pico Veleta, Onsala, Metsahovi

0.20.2 pcpc

A radio core + one sided jet is visible in recent VLBI observations at 86.2 GHz with a linear resolution of0.08 x 0.13 pc (HPBW) Giroletti et al. in prep.

Core: unresolved at 86 GHz size lower than 0.03 pc (gaussian fit)

1 Rs = 0.001 pc (M = 109 Mo)

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

Question: why the jet brightness is so low

in the 86 GHz image?

Steepening because of high magnetic field?

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)

M87

at 86 GHz (Krichbaum et al. 2006)

at 43 GHz (VLBA) (Ly et al. 2007)

MKN501 at 86 GHz

Jet velocity and orientation from data:

High velocity jet with Γ =15 and θ = 4o (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 4o to 10o - 15o to explain the limb-brightened structure radio structure and Γ decrease to 10 (δ 2.6) at 30 - 40 mas from the core (80-120 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)

25

20

15

10

5

Adiabatic model in the case of relativistic motion discussed by Baum et al. 1997. See also

Cotton et al. 1999, and Giroletti et al. 2004

Jet initial velocity

0.998 c

THANK YOU