X-ray Observations of Large Scale Jets in AGN

X-ray Observations of LargeScale Jets in AGND. E. Harris, SAOCollaborators:H. Krawczynski, C. Cheung, S. Jester, M. HardcastleE. Perlman, J. Biretta, A. Siemiginowska, H. Marshall,D. Schwartz, plus many others

outline• Part I: Introduction – Short Review ofcurrent situation.• Part II: Difficulties for application ofphysics• Part III: Jet Structurehotspots, continuous, and knotsKrakow - 2006 June 27

CREDO -1( a personal perspective)• Sync. emission is hopelessly mired in theuncertainty of the value of B: total E; pressure;halflife, etc. Very tenuous passage to N(E)• IC/CMB is not much better because Γ isuncertain. Throughout this talk I use lower caseγ for the Lorentz factor of the radiating electronsand upper case Γ for the bulk Lorentz factor ofthe jet. δ is the Doppler beaming factor.Krakow - 2006 June 27

Electron Halflives• τ = 10 13 yearsγ {B´2+ 40(1+z) 4 Γ 2 }• for Synchrotron; X-ray frequencies of 10 18 Hz,γ= 0.0005 √[ν(1+z)/B(1)] ≈ 10 7 ,and τ is of order a year.IC/CMB with Γ > 5 (often >10)γ={ 2x10 -6 / Γ } √ν and for ν=10 18 , γ ≈ 100and τ ≥ 10 5 yearsKrakow - 2006 June 27

CREDO -2The X-ray Emission Process forQuasar Jets• Whereas there is little debate about radio andoptical for both FRI and quasar jets, there is noconcensus for the X-rays from quasars and FRIIradio galaxies.• SYNC with γ ≈ 10 7 and halflife ≈ 1 year (like FRI);OR• IC/CMB with γ ≈ 100 and halflife ≥ 100,000 yearsKrakow - 2006 June 27

X-ray Emission from Jetsis a “Win-Win” Game• Either we get info about the very top end of therelativistic electron spectrum, N(E),• OR we learn about the very bottom end!• ******************************************************• NEITHER END IS ACCESSABLEBY OTHER MEANS******************************************************• and now for the bad news…..we don’t know which end we are looking at!Krakow - 2006 June 27

CREDO - 3• essentially all X-ray jets are single sided;hence the Γ,δ [of the emitting plasmas]are of order a few or greater.• The emitting plasmas consist of relativistic(“hot”) electrons, but the “fluid” responsiblefor the energy flow consists of cold pairs,normal plasma (p + e), or Poynting flux.Krakow - 2006 June 27

Part II: Difficulties of applying thephysics• We want to obtain the parameters of theemitting regions….the exponent of thepower law describing N(E); breakenergies; cutoff energies; B field strength;beaming factor, θ, & Γ. Plus all thederived quantities like energy content,pressure, etc.Krakow - 2006 June 27

Synchrotron Assumptions• is a valid concept; usually B eq• Emitting volume is same for all wavebands• SED is concave downwards, with cutoffs.• filling factor~1 (as opposed to filaments ofhigh B with particles both between andwithin the filaments )Krakow - 2006 June 27

IC/CMB assumptions• single emitting volume containing a singlePL extending from circa γ=50 to γ=500000• Γ is large enough to produce obs. X-rays• B eqrequired to pass from radio to N(E)• p=2α r+1 is the exponent of lower part ofN(E), as well as of the ‘observed’ part.Krakow - 2006 June 27

The next image……• shows the extent of the extrapolation (infrequency, or, top axis, electron Lorentzfactor) between the observed segment ofthe spectrum of a knot in a jet, and thesegment responsible for the X-rayemission for the IC/CMB process.• It also demonstrates that new radiotelescopes under development will help totest this extrapolation.Krakow - 2006 June 27

PKS 0637 – Quasar with JetKrakow - 2006 June 27

Emitting Volumes: 3C 273• We want to constructSED’s for several bitsof a jet. We constructphotometric regionsbased mainly on theX-ray morphology.• But when we use thesame regions foroptical and radio…Krakow - 2006 June 27

…the emitting volumes may notactually be the same size as for the• we have to assumethey are the same ifwe don’t have thesame resolution.X-raysKrakow - 2006 June 27

4C 19.44: global X/radiocorrespondence is good; however,in detail, this is not the case.Krakow - 2006 June 27

Emitting Volume:Multi zone models:• Laing and Bridle have modeled some FRIjets and argue for the necessity of velocitystructure across the jet• Celotti and others have suggested a fast(Γ>10) spine plus slower sheath on kpcscales.• Uchiyama (poster #49) and Jester et al.find that a single zone is inadequate forthe SED of parts of the 3C273 jet.Krakow - 2006 June 27

Emitting Volumes:Multizone ModelsThis permits more latitude for adequatelyfitting SED’s, but any 2 zone modelnormally precludes the critical testsafforded by comparison of radio, optical,and X-ray data.Krakow - 2006 June 27

Emitting volumes: Mavericks• While there isgenerally goodcorrespondencebetween bands, sometimes we find notableexceptions.• Here we see the radio(color) deviating fromthe X-ray (contours).Krakow - 2006 June 27

In the next slide…..• Note the prominent X-ray emission beyondknot C where the radio contours show akink to the north. In the bottom panel, wesee the hardness ratio for this featurediffers from that of knots B and C.Krakow - 2006 June 27

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PART III: Features• Hotspots• Continuous emission between knots• KnotsKrakow - 2006 June 27

Distinguishing Hotspots from Knots• Terminal HS where jetstops, but is emissionalways isotropic?• ‘Classically’ SSC explainsthe X-rays, but thereappears to be additionalemission.• 3C351: at least a factor of25 between1.4 GHzpower of N and S HS’s.• Hardcastle will discuss onFriday.Krakow - 2006 June 27

Continuous Emission between theknots• If synchrotron, requires distributedacceleration (e.g. magnetic acceleration orboundary layer shear acceleration, ref: ourhosts at this meeting)• Could be underlying IC/CMB component.• In either case we might expect α xto varybetween knots and inter-knot regions.Current evidence does not support this.Krakow - 2006 June 27

Inter-knot X-ray emission in M87Krakow - 2006 June 27

PKS 1127 @ z=1.1: most of the X-ray emission of the inner jet is notassociated with bright radio.Krakow - 2006 June 27

Cen A: another example ofdistributed X-ray emission, notalways associated with radio knots.Krakow - 2006 June 27

Conventional knots:shock acceleration• Downstream from the shock, we expect to‘loose’ the highest energy electronssooner than the lower energies and weassume that we can use distance from theshock as an ‘age’ indicator.• Sync: X-ray brightness should drop fasterthan radio.• IC/CMB: opt. & rad. should drop fasterthan X-rayKrakow - 2006 June 27

Alternatives to Shocks for Knots• CHANGE OF DOPPLER FACTOR:• from change of Γ (unlikely), or• from change of θ (e.g. helical trajectories)• ‘BURST’ TYPE EJECTION FROM SMBH.• CONTRACTION - EXPANSION (i.e. notnecessarily in a shock)Krakow - 2006 June 27

EXPANSION LOSSES• SYNCHROTRON• all electrons lose samefractional E• emissivity drops ∝B 2• N(E) is smaller for fixedobserving band.• there are 3 effectsreducing theemissivity!• INVERSE COMPTON• all electrons lose samefractional E• [u(ν) drops for SSC]• for IC/CMB, thereis only onecontribution todecay.Krakow - 2006 June 27

Compression/Expansion forsynchrotron emission with a fixedobserving band.Krakow - 2006 June 27

Knots from curved trajectory• Enhanced emissivity could arise from achange in the beaming factor.• The larger Γ required for IC/CMB modelsmeans that Q should have higher contrastknots than FRIs since the emission cone issmaller for larger Γ.Krakow - 2006 June 27

? – What path does the fluid follow• Straight line(‘ballistic’) ?• Helical ?• NB: a curvedtrajectory withbeaming is a goodway to explain theoccurrence of knots.It also relaxesconstraints on thejet angle to the l.o.s.Krakow - 2006 June 27

Digression: Sizes & LuminositiesGRB, μQ, FRI, FRII+Q jets are all verypretty; being long and narrow….. but theyare of vastly different scales! Don’t expectidentical physics!Krakow - 2006 June 27

Relative sizes.microQ and M87Krakow - 2006 June 27

3C273 at same brightness scale asM87jet outside the galaxyM87 jet within galaxyKrakow - 2006 June 27

Compare 3C 273 with M87:Parameters for a bright knot3C 273• 0.5” ≈ 1300pc• L x≈ 10 43 ergs/s• B x≈ 0.27 evps/0.05”p• α x≤ 1M87• 0.5” ≈ 38pc• L x≈ 10 41 ergs/s• B x≈ 5.5 evps/0.05”p• α x≥ 1Krakow - 2006 June 27

3C 273 compared to PKS1127 @z=1.1Krakow - 2006 June 27

Or all together for a single view:Krakow - 2006 June 27

Comparative Sizes: log scale(missing from this plot are typical VLBI extragalactic jets)Krakow - 2006 June 27

Projected vs. Physical Lengthvia ‘best guess’ θKrakow - 2006 June 27

M87 as an example of synchrotron• Offsets – comparing radio contours on an X-rayimageKrakow - 2006 June 27

Morphology: X-ray & Radio• X-ray peaks upstream of radio in knots D & FKrakow - 2006 June 27

Projections• - radio• optical• X-rayKrakow - 2006 June 27

M87 Spectral Changes• Downstream from the core region, andalso from knot A, the X-ray spectrumsoftens.• The next slide shows the X-ray jet in 3 X-ray bands, with brightness labels.Krakow - 2006 June 27

Flux maps: 3 bandsKrakow - 2006 June 27

Offsets in 3C 273 and PKS1127• In a sense, these sort of offsets seem tobe scale invariant since we see similarproperties for these powerful sources, buton a larger scale.Krakow - 2006 June 27

3C273 offsetsKrakow - 2006 June 27

PKS 1127 offsetsKrakow - 2006 June 27

offsets & progressions=2 sides ofsame coin• If we were viewing 3C273 at z=1.1, the jetwould be unresolved, but there would be avery obvious offset between peakbrightnesses: X-ray peaking closer to thequasar; optical and radio progressivelyfurther downstream.• i.e. the internal (unresolved) structure of aknot of PKS1127 could look like this…..Krakow - 2006 June 27

3C273: X, Opt, & RadioKrakow - 2006 June 27

Variability• In addition to M87, variability is also seenin features of Cen A (Kraft et al.)• The knots of powerful Q are generally toolarge physically for this test.Krakow - 2006 June 27

Project: 4 years of monitoringthe M87 jet with Chandra• The Nucleus varies,as expected.• HST-1 varies andhas peaked at 50x the2000Jul level.• knot D probablyvaries.• knot A shows a milddecay.Krakow - 2006 June 27

HST-1 LightcurvesKrakow - 2006 June 27

Decay Time• X-ray: suspect that τ(sync)

VLBA dataKrakow - 2006 June 27

What we find…2.8c apparentproper motionKrakow - 2006 June 27

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1994-1998; same thing but opticalKrakow - 2006 June 27

Superluminal optical featuresKrakow - 2006 June 27

Parameters for components• 1994-1998 optical• nucleus->hst-1: 0.87’’• β(leading): 0.84±0.1• β(following): 4 to 6• size: ≤ 4pc• overall size: 24pc• 2005 radio• nucleus->hst-1: 0.86”• β(leading): 1.0±0.1• β(following): 2.8• size: 10mas or 0.7pc(expected 1mas, 0.1pc)• overall size: 3pc• date when following wasat leading: 2001 SepKrakow - 2006 June 27

The Red Queen’s RaceThe upstream edge of HST-1 appears tobe moving away from the core with avelocity close to c; yet 10 years later, ithas not advanced.Krakow - 2006 June 27

FINKrakow - 2006 June 27