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

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 ‣ theory • Impact of structured jets: • Giant FRIs: NGC 6251 • Y oung radio sources: 3C 186 2 Friday, July 1, 2011

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 ) ; ( Giroletti+2004 ) ‣ 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 ) ; ( Edward&Piner2002 ) more than one - zone radiatively relevant? 3 Friday, July 1, 2011

Jet Structure: observations & theory • Models for a structured jet: ✤ axial structure: the jet decelerates as it Γ expands ( Celotti+2001, Georganopoulos&Kazanas 2003 ) ✤ radial structure: the jet develops a spine - layer structure ( Stawarz&Ostrowski 2002, Ghisellini+2005 ) Ghisellini, Tavecchio, Chiaberge 2005 ✤ and more: colliding shells and jet - in - a - jet ( Dermer 2010, Giannios+2009,2010 ) Γ The di ff erent regions can radiatively interacts with consequences also for the jet dynamics ( see Compton rocket e ff ect, Sikora+1996, Ghisellini+2005 ) 4 Friday, July 1, 2011

Jet Structure • 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 Friday, July 1, 2011

The Giant: NGC6251 z=0.024, 1.9 Mpc dimensions (Perley 1984) NGC 6251 is one of the radio galaxies detected in the first year of Fermi - LAT observations ( EGRET 3EG J1621+8203 source association, Mukherjee+2002 ) : • bulk of the gamma - ray emission likely Perley+1984 Chiaberge+2003 from the nuclear region ( <kpc ) • Nuclear SED dominated by jet emission ( Chiaberge+2003, Guainazzi+2003, Ghisellini+2005 ) ; 6 Friday, July 1, 2011

The Giant: NGC6251 Egret • Single - zone SSC: θ =25 o Γ =2.4 Fermi- R ∼ 10 17 cm B ∼ 0.04 G LAT N ( γ ) =K γ - p p1=2.76 p2=4.04 K ∼ 2 × 10 6 cm - 3 γ break =2 × 10 4 γ min =250 γ max =2 × 10 5 ✤ a slow ( Γ =2.4 ) and particle - dominated ( U e /U B >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? 7 Friday, July 1, 2011

The Giant: NGC6251 Synch layer Ghisellini, Tavecchio, Chiaberge 2005 EC layer • Layer: Γ =2.4, B=0.7 G, SSC layer R ∼ 10 17 cm, h ∼ 3 × 10 16 cm Synch spine • Spine: Γ =15, B=1.8 G, SSC spine R ∼ 10 16 cm, h ∼ 10 15 cm ✤ fast and light ( near - to - equipartition ) jet: ‣ high radiative dissipation ( L rad ~1/3 L jet ) : the jet should decelerate ( but Mpc scales! ) ; ‣ high - energy variability? 8 Friday, July 1, 2011

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 oung radio sources Friday, July 1, 2011

The little: CSS Quasar 3C186 • Radio powerful L radio ∼ 10 46 erg s - 1 • High - z X - ray cluster environment ( Siemiginowska+2005,2010 ) • Radio - loud but relatively X - ray weak L ( 2 - 10keV ) ∼ 1.2 × 10 45 erg s - 1 Which is the origin of the X - ray emission? ( Siemiginowska+2008 ) 10 Friday, July 1, 2011

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 k2/knot inner blazar - like component can be Compton scattered in the external slow moving knot ( Celotti+2001 ) ; 11 ( Spencer+1991 ) Friday, July 1, 2011

The little: CSS Quasar 3C186 ( Spencer+1991 ) IC seed photons in the jet ( knot ) comoving frame: k3 k2 h.s. 12 Friday, July 1, 2011

The little: CSS Quasar 3C186 Jet ( knot ) SED: The observed X - ray emission can be explained as IC emission from the jet only if we assume a complex jet structure 13 Friday, July 1, 2011

The little: CSS Quasar 3C186 ✤ Implications on the jet evolution: blazar-like k 2 component L e (erg s − 1 ) 3 . 2 × 10 46 2 . 0 × 10 45 L p (erg s − 1 ) 1 . 1 × 10 48 3 . 5 × 10 46 L B (erg s − 1 ) 2 . 1 × 10 47 7 . 8 × 10 44 L kin (erg s − 1 ) 1 . 4 × 10 48 3 . 7 × 10 46 L r (erg s − 1 ) 1 . 1 × 10 47 1 . 8 × 10 45 • The jet dissipates the bulk of its power at small scales and decelerates ( FRII jet speed at kpc scales?? ) ; • Jet power >> disk luminosity ( L disk ~10 47 erg s - 1 ) : the source - environment interactions are dominated by the jet/radio mode ( see FSRQs Ghisellini+2010 ) 14 Friday, July 1, 2011

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 e ffi cient 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

High-Energy emission - II 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. Satellite XMM-Swift Combined fit a Obs date 0.8 +0 . 4 k B T (keV) − 0 . 2 norm b ( × 10 − 5 ) 3 4 ± 2 N H ( × 10 21 cm − 2 ) 0 1.1 ± 0.1 1.89 ± 0.04 Γ norm c ( × 10 − 3 ) 1 1.18 ± 0.05 n d – 1 XMM n d – 0.60 ± 0 . 04 Swift 1 X-ray flux decreases of about 40% between n d – 0.45 ± 0.05 Swift 2 the XMM (2002-03) and the first Swift n d – 0.44 ± 0.04 Swift 3 (2007-04) observations and further 15% before χ 2 (d.o.f) 455(430) the second Swift observation (2009-05) Friday, July 1, 2011

Constraints on the main parameters of the gamma-ray emitting region Gamma-ray region dimensions:  VLBI observations: ≤ 0.20 mas + VLBI J=100:1 β >0.78 within 6 mas variability (~10 17 -10 18 cm) (Jones et al. 1986, 10 o < θ <40 o Evans et al. 2005)  similar upper limits from X-ray variability v a >1.2c studies (Jones & Wehrle 1994) Jet inclination ( θ ) and Bulk motion ( Γ ): P c =0.4 Jy P tot =5.3 Jy  jet sidedness (J) (VLA 1.37, 1.48, 1.66, 4.85 GHz maps, Perley et al. 1984) ;  Apparent velocity ( β a );  Core Dominance (see Giovannini et al. 2001) Friday, July 1, 2011

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, L 151 , in kinetic power (Willott et al. 1999) 151 L kin = 3 × 10 45 f 3 / 2 L 6 / 7 151 erg s − 1 W Hz sr . In the revised formu 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: L kin =(8-2) × 10 44 erg s -1 roughly in agreement with the model estimates Friday, July 1, 2011