Fabrizio Tavecchio - INAF/OA Brera

1. Probing relativistic particles in jets Fabrizio Tavecchio - INAF/OA Brera

2. Relativistic particles … Standard scenario: particle acceleration through Fermi I type mechanism at a shock front (“diffusive shock acceleration”): N(g) = Nog-n n=2 strong, non-relat. shocks; n=2.2 relativistic case g > ginj>>1 depending upon conditions in the plasma g < gmaxlimited by balance acc. rate = cooling rate n=2 also expected from cooling of high-energy e Broken-power law distributions expected from continuous injection + cooling But n2=n1+1 ~3 for blazars we need n2=4-5

3. blazar radiogalaxy, RL QSOs Urry & Padovani 1995 … in jets Emission lines EW>5 Å FSRQ EW<5 ÅBL Lac

4. Spectral Energy Distribution and emission mechanisms Radio IR Opt UV X MeV GeV Inverse Compton (also possible hadronic models) Synchro

5. Log N(g) gb n1 n2 Log g The electron energy distribution ginj Cooling Cold particles Total number: jet power ? g max Acceleration ?

6. The“blazarsequence” FSRQs BL Lacs Simbol - X Fossati et al. 1998; Donato et al. 2001 But see e.g. Padovani 2007

7. Log N(g) gb n1 n2 Log g Low power blazars: probing the high energy end

8. Log N(g) gb n1 n2 Log g nC =n’s gb2 d Log nL(n) ns nC nL(n)~s T c Usyn N(g)gg2 V d4 a1 a1 a2 a2 Log n The simplest model - SSC Log Usyn(n) + n’ s a1 a2 Log n

9. Low power blazars: probing the high energy end Tavecchio et al. 2001 Maraschi et al. 1999 Courtesy PO Petrucci

10. 1999 Mkn 421 TeV (Whipple) 2000 X-rays TeV (Whipple) TeV (Whipple) Maraschi et al. 1999 X-rays Fossati et al., in prep

11. Mkn 421 XMM-Newton Dec. 2002 Soft Medium Hard Ravasio et al. 2004 Signatures of cooling/acceleration processes are expected. The best way to detect them is through X-ray monitoring of TeV blazars, since we can probe the synchrotron emission of the most energetic electrons. Dt(hard/soft)~1000 s If acc. due to shocks: B~0.6 d10-1 G

12. TeV spectra and intergalactic absorption

13. Aharonian et al. 2006 using recent HESS data of the BL Lac 1101-232 (z=0.186) found that, even assuming the lowest level of the IR background (estimated through galaxy counts), the de-absorbed spectrum is very hard (G<1.5). The broad-band X-ray spectrum is required to constrain the intrinsic slope

14. The broad-band X-ray spectrum is required to constrain the intrinsic slope

15. High-Energy Observatories 2004-2020

16. Log N(g) gb n1 n2 Log g High power blazars: probing the low energy end

17. Log N(g) gb n1 n2 Log g nC =n’ogb2 d Log nF(n) ns nC nL(n)~s T c Uext N(g)gg2 V d4 a1 a1 a2 a2 Log n The simplest model - EC Log Uext(n) Broad line region, Disk + n’ o n’ o = G no Log n

18. High power blazars: probing the low energy end

19. Variability … A hard X-ray flare of 3C454.3 ISGRI 20-40 keV Pian et al. 2006 Luigi Foschini’s talk

20. Extremely hard slopes… Extremely hard! n=1.5! SWIFT/BAT, 9-month survey Suzaku Sambruna et al. 2006 Tavecchio et al. 2007, in press

21. Cold matter: X-ray signatures Celotti, Ghisellini & Fabian 2007 Broad band spectra necessary to obtain effective constraints

22. Conclusions The (hard) X-ray band is crucial to address several problems related to the origin and dynamics of relativistic particles in jets Low energy blazars: probe of the high energy end; particle acceleration; help for the estimate of the CIRB High power: investigation of low energy electrons; variability; cold particles