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Physics of Relativistic Jets

Physics of Relativistic Jets. Jun KATAOKA (Tokyo Tech, JAPAN). Outline. Shock Physics in Relativistic Jets. Jets in Gal/ext-gal objects. Shock acceleration in general. Learning from AGN jets (“blazars” vs “Radio Gal”). Acceleration in sub-pc jets. Jet Structure in large-scale jets.

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Physics of Relativistic Jets

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  1. Physics of Relativistic Jets Jun KATAOKA (Tokyo Tech, JAPAN)

  2. Outline • Shock Physics in Relativistic Jets • Jets in Gal/ext-gal objects • Shock acceleration in general • Learning from AGN jets (“blazars” vs “Radio Gal”) • Acceleration in sub-pc jets. • Jet Structure in large-scale jets. • Comments on GRB jets (vs. AGN) • Warning signal on the standard model. • Acceleration in small-scale B-field.

  3. GRB m-QSO AGN Galactic/Extragalactic Jets • Relativistic jets – exciting, powerful, but least understood phenomena. • A number of compact objects (Gal/ext-gal) have jets with various sizes. • size : 1AU ~ 1Mpc, power : 1040~1052erg/s, Gjet : a few ~ 1000 • similarities – underlying physics are the same! • Shocks in jets are most promising site of particle acceleration.

  4. ~ 30 Rg Strong B-field for launching “bulk” motion of jet plasma “random” motion & acceleration non-thermal radiation Junor+ 99 Why AGN Jets? • scale size: Rg ~ 1013 cm ~ 1AU. jet launching site (~30 Rg) (jet structre, opening angle etc … with the low-E VLBI observations) • total power : Ptot ~ 1044-48 erg/s • Etot ~ 1058-60 erg. • # density : n ~ 10-7 AGN/Mpc3 sufficient for CR acceleration. What makes the relativistic outflow?

  5. B-field particle vup vdown Shock Acceleration in Jets • Coulomb collision lc = 1.6 x 104 T82 nth,-4-1L-1 kpc (T = 108 T8 [K], nth = 10-4 nth,-4 [cm-3]) • Gyro radius rL = 1.2 x 10-13 T8-1/2 B-6-1 kpc (B = 10-6 B-6 [G]) • Collisionless shock in AGN jets. rL ~10-14 kpc << R~ kpc << lc~104 kpc shock in AGN : lc ~10-15 cm << R~103 cm << rL ~106 cm c.f., ground exp : • Shock acceleration process: En = Eo (1+x)n ~ (1+ 4b/3)n N(g) = g-s, where s ~ 2. ...But where B comes from?, really 1st0rder ? What is the shock!

  6. N(g) Sync Emissivity thermal non-thermal low B IC high B g gmin gmax radio X-ray g-ray Standard Picture • gmin What fraction of “seed particles” injected? • gmax How efficient the “accelerator” is ? tacc = (20c/3vs2)rgz∝Ee tcool = [ Ee/ (dEe/dt) ] ∝Ee-1 “Non-thermal” emission • We can derive B-field strength by Sync/IC ratio as For a given Lsync, LIC  B-2 B, gmax , size etc…

  7. Learning from AGN Jets

  8. low power (FRI, BL Lac) radio galaxies (large q) high power (FRII, QSO) Blazars (small q) B.H sub-pc kpc ~ Mpc AGN Jet: review • Viewing angle is a key to identify various classes in AGNs. • Blazars’ emission come from the most inner part of the jet, • via the internal-shock in sub-pc jet. • Large scale jets in powerful radio galaxies (FR II/QSO) extend to • Mpc scale: external-shock?

  9. X-ray optical GeVg TeVg ERC SSC Takahashi+ 96, Kubo+ 98 Kataoka+ 99-02 LE peak (synchrotron) HE peak (Inv. Comp) LE HE Multiband SED of Blazars (sub-pc jet) • Multi-band campaigns organized by ASCA,SAX,RXTE … • - confirm “double peak” structure over two decades in freq! • Measurement of jet speed (VLBI) : Gjet > (b2app +1)1/2 • Rapid time variability : R ~ ctvar d D ~ RGjet~ sub-pc B ~ 0.1 G, Gjet ~ 10, ue ~ 10 uB

  10. Extreme Blazars 1.4x108 d101/2B0.1-1/2 x-1/2 bsh g max ~ Search for “Extreme Blazars” XEUS Ghisellini+ 98, Kubo+98 Max E 1TeV 10mJy 1GeV luminosity • Clear correlation between luminosity and peak freq : nsync∝Lsync-1.5 nmax ~ 10 MeV • Significant fraction are still hidden - only “visible” in hard X-rays! . • “Extreme” particle accelerators - though very faint (5x10-13 erg/cm2/s • @50keV) NeXT/XEUS can easily detect “dark accelerators”.

  11. Q0836+710 (z=2.17) If z=10 Log nFn gmin =1 3 10 Distant Blazars with XEUS/NeXT ? Sambruna+ 06 Swift J0746 (z = 2.98) • “MeV-peaked” blazars at z  10 can be detected (if exists!). • Cosmological evolution of blazars - relation to SFR? Where the QSOs gone? cosmic X/g-ray BGD? gmincan be observed in X-rays for distant QSOs. - kinetic power of jet? - jet content (e-e+ or e-p)? Accel. fraction ? (e.g., Kino & Takahara 03)

  12. 1 1 Lkin ~ p R2 c G2jet (ue + uB ) Lrad ~ ~ G2BLK Lkin 100 Lrad ~ 4p R2 c (uB + urad) Large-scale jets in X-rays • Only ~ 1% of kinetic energy would be converted into radiation • in sub-pc jet, consistently with “internal shock” scenario. • Jet interaction, heating, and structure formation in cluster plasma. Chandra obs provides direct probe to physics in large-sale jets FR II (Cygnus A) Jet model : Begelman & Cioffi 89 Chandra : Wilson+ 00

  13. nFn nFn nFn X-ray IC/CMB (ue = uB) X-ray X-ray radio radio radio n n n Variety of Large Scale FR-II Jets 3C273 Pictor A 3C219 Jet-knot hotspot lobe • Double peaks – IC/CMB emission for X-rays? • Both hotspots and radio-lobes suggest ue ~ uB, while jet-knots • are generally too bright in X-rays. • Need of Doppler boosting for jet-knots: LIC/CMB ∝ d3 ? (Tavecchio+ 00, Sambruna+ 04)

  14. blazars Radio galaxies 100 1 10 0.1 Beaming factor d Relativistic Large-scale Jet? Kataoka & Stawarz 05,ApJ knot hotspot lobe 50 d = 10 10 Beaming factor d 1 Gjet = 3 Gjet = 30 Gjet = 10 30 60 90 0 q[deg] • d ~ 10 indeed required only for the jet-knots. • … BUT, enhancement due to beaming is hardly expected • in radio galaxies as viewing angle is very large! • If we give up “ue ~ uB” assumption,ue ~ 108 uBrequired !. Death of boosted IC/CMB scenario?

  15. SPITZER • Detection @50 keVEe >1015 eV and/or Ep >1018 eV! • X-ray polarization?Evidence for “exsotic” Sync X-ray spectrum. Evidence for “Sync X-ray Jet” 3C273 Uchiyama,+ 06, also Jester+ 06 • SPITZER obs of3C273 jetconfirms that the optical jet is dominated by • the 2ndSync component, as it strongly polarizes Popt = 15 % (~ Pradio). • A smooth connection between optical and X-rays, suggest X-rays are • also Sync (leptonic? hadronic? still under debate!)

  16. 2 3le c ~ 5x109 g8 B-1100mV-2A,8 [s] tacc~ c VA 2 L c ~ 6x105 g8-1B100mL2100pc [s] tesc~ 3 VA le N(g) g gmax Turbulent Acceleration? layer spine • Stratified jet – “spine” + “layer”. • Accel. process in layer is quite different! CR tesc/tcool ~ 107 (B100mG)3 (l100pc)2 z-1 where z = UB/UT • If field is very turbulent (z ~ 1), electrons • “pile-up” as it never escape from the region. different spectra in spine/layer. observed hump in X-rays? Ostrowski 00, Stawarz & Ostrowski 02

  17. Jet center 0.4-8 keV Diffuse Jet Transverse Profile of Cen-A X-ray Jet Kataoka+ 06, ApJ 1keV flux aX 25 45 Position angle • Ideal laboratory - “nearest” AGN (dL = 3.4Mpc, 1” = 18 pc). • “double-horn” profile in thetransverse direction. • Uniform spectra over the jet, except for jet edges. • tsyn ~ 20 B-3/2 E-1/2[yr] Acceleration over the jet volumes (NOT exclusive to bright jet-knots!) 100m 10keV Jet profile in hard X-rays provides direct hints of CR accel. !

  18. Brief comments on GRB Jets

  19. “Blazar” region lobe, hotspot assumption, but GLAST an detect IC of GRBs eB, ee Gjet Ltot Dt R B GRB (prompt) 1052 erg/s 10s 10-5 pc >100 106 G ~ 0.1 AGN (blazar) 1046 erg/s 1014s 0.01pc 10 0.1 G ~ 0.1 GRB vs AGN Jets • The standard model of g-ray prompt emission is still rough, but • somehow explains afterglow emission well. • AGN vs GRB: typical parameters:

  20. Preece+98 a=-2/3 Ebr Inhibited Spectral Index:a GRB spectrum: prediction • Observed GRB spectrum often agree • with Sync shock model, BUT… • significant # of GRBs “inhibited”? • (death-line problem) • spectral break is too sharp? Problems due to low sensitivity of BATSE below 50 keV ?

  21. HETE-II Observation of GRB020813 Sato+ 05 Inhibited • Spectral measurement in wide energy band: 2-400 keV • Sync self-abs cannot explain a < -2/3 spectrum. tSSA~ 7.3x10^(-6) R13n8 B62/3g-2/3100G-31000n19-5/3<< 1 • IC model of X-ray production also rejected. Violation of standard picture, e.g., eB << 1 ? Why so different from AGN jets ?

  22. “Jitter” radiation in tangled B-fields Medvedev 00 • B-field is randomly tangled: • deflection a << beaming Dq “jitter” radiation (Landau & Lifshits 75) • Hard spectrum + sharp break njit~ 1010 g3/2m G2jet ~ 1017-20 [Hz] n1 (n < njit) Fjit ∝ Death line n-(p-1)/2 (n > njit) n-(p-1)/2 • Tangled field in GRB jet ? • - Rapid expansion! • - Not enough time for growth of • large-scale, regular fields ? n1 Feedback for the theory of collisionless shock, in general.

  23. Summary • Physics of AGN jets are being much clear thanks to previous • ASCA/BeppoSAX/RXTE, but nature of large scale X-ray jets is • still open, even after advent of Chandra/XMM. • Many of jet physics will be deeply probed in NeXT decade. • CR acceleration and what is collisionless shock? • GRB physics is also still unclear, especially for prompt emission. • Important hints on the field and formation of relativistic jets. Future observations with XEUS/NeXT… and GLAST etc will give us a clear answer of “what is the jet?”

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