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Probing the velocity structure of relativistic jets G. Migliori ( - - PowerPoint PPT Presentation

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Probing the velocity structure of relativistic jets G. Migliori ( SAO ) A. Siemiginowska P . Grandi A. Celotti R. Mukherjee E. Torresi C. Dermer J. Finke 1 Friday, July 1, 2011 Overview Introduction: jet structure observations

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SLIDE 1

Probing the velocity structure of relativistic jets

  • G. Migliori (SAO)
  • A. Siemiginowska

P . Grandi

  • A. Celotti
  • R. Mukherjee
  • E. Torresi
  • C. Dermer
  • J. Finke

1

Friday, July 1, 2011

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SLIDE 2
  • Introduction: jet structure
  • observations
  • theory
  • Impact of structured jets:
  • Giant FRIs: NGC 6251
  • Y
  • ung radio sources: 3C 186

Overview

2

Friday, July 1, 2011

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SLIDE 3

Jet Structure: observations & theory

  • Clues for a complex structure in

extragalactic relativistic jets in AGNs:

  • comparative studies on parent populations:

FRI/BL-Lac sources (Chiaberge+2000);

  • radio observations of a limb-brightening

morphology (Swain+1998,Giroletti+2004..);

  • subluminal velocities in TeV BL-Lacs

(Marscher+1999,..., Edward&Piner2002) and gamma-ray/TeV detection of radio galaxies (Steinle+1998,Mukherjee+2002, Aharonian+2003);

3

more than one-zone radiatively relevant?

(Giroletti+2004) (Edward&Piner2002)

Friday, July 1, 2011

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SLIDE 4

Jet Structure: observations & theory

  • Models for a structured jet:

✤ axial structure: the jet decelerates as it

expands (Celotti+2001, Georganopoulos&Kazanas

2003) ✤ radial structure: the jet develops a spine-

layer structure (Stawarz&Ostrowski 2002,

Ghisellini+2005)

✤ and more: colliding shells and jet-in-a-jet

(Dermer 2010, Giannios+2009,2010) 4

The different regions can radiatively interacts with consequences also for the jet dynamics (see Compton rocket effect, Sikora+1996, Ghisellini+2005)

Ghisellini, Tavecchio, Chiaberge 2005

Γ Γ

Friday, July 1, 2011

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SLIDE 5
  • Implication of a structured jet in two radio sources at

the extremes in terms of:

  • size/age (Mpc/kpc scales)
  • disk luminosity (FRI/ADAF, FRII/Sakura-Sunjaev disk)
  • environment (external-photon poor/rich)

5

Jet Structure

Friday, July 1, 2011

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SLIDE 6

The Giant: NGC6251

NGC 6251 is one of the radio galaxies detected in the first year of Fermi-LAT

  • bservations (EGRET 3EG J1621+8203

source association, Mukherjee+2002):

  • bulk of the gamma-ray emission likely

from the nuclear region (<kpc)

  • Nuclear SED dominated by jet

emission (Chiaberge+2003, Guainazzi+2003,

Ghisellini+2005);

(Perley 1984)

6 z=0.024, 1.9 Mpc dimensions

Chiaberge+2003 Perley+1984

Friday, July 1, 2011

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SLIDE 7

7

The Giant: NGC6251

  • Single-zone SSC:

θ=25o Γ=2.4

R∼1017 cm B∼0.04 G N(γ)=Kγ-p p1=2.76 p2=4.04 K∼2×106 cm-3 γbreak=2×104 γmin=250 γmax=2×105

Fermi- LAT Egret

✤ a slow (Γ=2.4) and particle-dominated (Ue/UB>400) jet?

  • Γ lower than for BL Lac sources (similar results in Chiaberge+2003 and LAT detected

misaligned AGNs, NGC1275:Abdo+2009, M87:Abdo+2009,CenA:Abdo+2010);

  • the jet cannot be magnetically confined on pc-scales (recollimation mechanism

required?);

✤ or (at least) one more emitting region w.r.t. the classical blazar-like one?

Friday, July 1, 2011

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SLIDE 8

8

The Giant: NGC6251

  • Layer: Γ=2.4, B=0.7 G,

R∼1017 cm, h∼3×1016 cm

  • Spine: Γ=15, B=1.8 G,

R∼1016 cm, h∼1015 cm

Synch layer Synch spine SSC spine SSC layer EC layer

Ghisellini, Tavecchio, Chiaberge 2005

✤ fast and light (near-to-equipartition) jet:

  • high radiative dissipation (Lrad~1/3 Ljet): the jet should decelerate (but Mpc scales!);
  • high-energy variability?

Friday, July 1, 2011

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SLIDE 9

Radio-loud quasars

  • Nature of the high energy emission in RL QSOs
  • non-thermal X-ray component correlated to the quasar radio-

loudness

  • radio vs X-ray: X-ray emission less beamed than radio (Miller+2011)

=> hints for a jet structure?

  • Y
  • ung radio sources

Friday, July 1, 2011

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SLIDE 10
  • Radio powerful

Lradio∼1046 erg s-1

  • High-z X-ray cluster

environment

(Siemiginowska+2005,2010)

  • Radio-loud but

relatively X-ray weak

L(2-10keV)∼1.2×1045 erg s-1

10

The little: CSS Quasar 3C186

(Siemiginowska+2008)

Which is the origin of the X-ray emission?

Friday, July 1, 2011

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SLIDE 11

11

The little: CSS Quasar 3C186

  • Test hypothesis: the bulk of the X-ray emission is produced by the

jet;

  • SED modeling considers:

✤ the dense nuclear environment

(external Compton of nuclear UV and IR photons);

✤ the jet decelerates while it expands

(two emitting regions):

  • the synchrotron photons from the

inner blazar-like component can be Compton scattered in the external slow moving knot (Celotti+2001);

k2/knot (Spencer+1991)

Friday, July 1, 2011

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SLIDE 12

12

The little: CSS Quasar 3C186

IC seed photons in the jet (knot) comoving frame:

(Spencer+1991)

k2 k3 h.s.

Friday, July 1, 2011

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SLIDE 13

13

The little: CSS Quasar 3C186

Jet(knot) SED: The observed X-ray emission can be explained as IC emission from the jet

  • nly if we assume a complex jet structure

Friday, July 1, 2011

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SLIDE 14

✤ Implications on the jet evolution:

14

The little: CSS Quasar 3C186

blazar-like k2 component Le (erg s−1) 3.2 × 1046 2.0 × 1045 Lp (erg s−1) 1.1 × 1048 3.5 × 1046 LB (erg s−1) 2.1 × 1047 7.8 × 1044 Lkin (erg s−1) 1.4 × 1048 3.7 × 1046 Lr (erg s−1) 1.1 × 1047 1.8 × 1045

  • The jet dissipates the bulk of its power at small scales and decelerates (FRII jet

speed at kpc scales??);

  • Jet power >> disk luminosity (Ldisk~1047 erg s-1): the source-environment

interactions are dominated by the jet/radio mode (see FSRQs Ghisellini+2010)

Friday, July 1, 2011

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SLIDE 15

Conclusions

  • W

e investigated the scenario of a structured jet for a giant FRI source and a young powerful FRII quasar

  • A structured jet can be radiatively very efficient in the

high-energy band

  • This implies a strong deceleration of the jet at kpc

scales: consequences on the source evolution?

  • The jet kinetic power in a structured jet can exceed the

disk emission: which is the jet role in the environment- source feedback mechanism?

15

Friday, July 1, 2011

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SLIDE 16

High-Energy emission - II

Satellite Obs date kBT (keV) normb (×10−5) 3 NH ( ×1021 cm−2) Γ normc ( ×10−3) 1 nd

XMM

nd

Swift1

nd

Swift2

nd

Swift3

χ2(d.o.f) XMM-Swift Combined fita 0.8+0.4

−0.2

4±2 1.1±0.1 1.89±0.04 1.18±0.05 – 1 – 0.60±0.04 – 0.45±0.05 – 0.44±0.04 455(430)

Nuclear region - XMM & Swift data: temporal analysis results:

  • no variability on short (hours) timescales (ie within the single observations);
  • years/month flux variability:
  • simultaneous fit of the XMM and 3 Swift observations with a composite (absorbed

pow+ thermal model);

  • n is energy independent factor which allow to compare the 4 datasets.

X-ray flux decreases of about 40% between the XMM (2002-03) and the first Swift (2007-04) observations and further 15% before the second Swift observation (2009-05)

Friday, July 1, 2011

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SLIDE 17

Constraints on the main parameters of the gamma-ray emitting region

Gamma-ray region dimensions:

VLBI observations: ≤0.20 mas + VLBI

variability (~1017-1018 cm) (Jones et al. 1986,

Evans et al. 2005)

similar upper limits from X-ray variability

studies

Jet inclination (θ) and Bulk motion (Γ):

jet sidedness (J) (VLA 1.37, 1.48, 1.66, 4.85

GHz maps, Perley et al. 1984) ;

Apparent velocity (βa); Core Dominance (see Giovannini et al. 2001)

va>1.2c (Jones & Wehrle 1994) J=100:1 within 6 mas Pc=0.4 Jy Ptot=5.3 Jy β>0.78 10o<θ<40o

Friday, July 1, 2011

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SLIDE 18

Jet kinetic power

  • we test the assumptions on the jet kin. power using pdV work

necessary to form the lobes against the surrounding gas: ➡ the relation to convert the radio luminosity at 151 MHz, L151, in kinetic power (Willott et al. 1999)

f accounts for systematics underestimates intrinsic to the technique. f=10-20 for a sample of FRIs and FRIIs (Hardcastle et al. 2007).

In this way we obtain: Lkin=(8-2)×1044 erg s-1 roughly in agreement with the model estimates

151

Lkin = 3 × 1045f 3/2L6/7

151 erg s−1

W Hz sr . In the revised formu

Friday, July 1, 2011