High energy emission from jets – what can we learn?

1. High energy emission from jets – what can we learn? Amir Levinson, Tel Aviv University Levinson 2006 (IJMPA, review)

2. Some open questions • Acceleration and collimation mechanisms? (constraints on Doppler factor from γ-ray and low energy emission, e.g., existing limits for TeV BL) • On what scales dissipation of the bulk energy occurs and how? Internal shocks ? Recollimation shocks ? Dissipation of Poynting flux ? (variability of VHE γ-ray emission + multi waveband obs.) • Jet composition ? (probes: cosmic rays; neutrinos)

3. Sources of UHECRs and neutrinos ? (probes of new physics?) If UHECRs are produced in astrophysical sites then emission of high energy neutrinos is expected

4. Target photons: synchrotron and /or external • Electromagnetic: synchrotron, IC, pair production • Hadronic: photopion production, nuclear collisions The basic picture blazar MQ

5. magnetic field Total energy density baryon density Scaling with dimensionless jet parameters

6. parameter

7. External radiation field

8. Intrinsic synchrotron intensity

9. Confinement limit • At small radii the proton energy may be limited by losses due to photopion production, and can be well below the confinement limit. Threshold energies for interaction with peak synchrotron photons Energy scales

10. Various energy scales energy rest frame rest frame observed observed

11. Electromagnetic emission

12. -spheric radius versus energy: external synchrotron GLAST relevant to 3c279 Pair production opacity

13. r0 MQ r(cm) 1011 107 109 AGN 1019 1014 1017 Conclusion: if dissipation occurs over a wide range of radii then flares should propagate from low to high -ray energies. Will be constrained by GLAST

14. Doppler factor redshift γ- ray energy measured synchrotron flux Constraints on Doppler factor and radius of emission zone. Upper limit on neutrino yield Further constriants from variability using multi-band obs. γ-spheric radius for target synchrotron radiation field

15. Example Inconsistent with superluminal motions on pc scale and source statistics. Jet decelerates ? Other reasons ?

16. Hadronic emission

17. in AGNs, Microquasars (except perhaps for HMXBs wherestellar wind may contribute) May be important in GRBs Inelastic nuclear collisions p + n  p + p + -  - +   e- + e +  +  p + n  n + n + +  + +   e+ + e +  +  p + n  p + n +0   + 

18. ext sync dissipation radius Photomeson production p +   + + n  + +   e+ + e +  +  p +   0 + p   +  π - sphere

19. Relations between photo-  production and γpair-production Same target photons for both processes.

20. Opacity ratio (target: synchrotron photons) eg =10 GeV 100 GeV 1 TeV 10 TeV Mrk 421

21. eg =10 GeV eg =100 GeV eg =1 TeV eg =10 TeV Opacity ratio (target: external radiation field)

22. Conclusions • Regions of significant photo- opacity are opaque to emission of VHE gamma rays. • Highly variable VHE -ray sources, in particularTeV blazars are not good candidates for km3 neutrino detectors. • In regions of high photo- opacity, - rays produced through π0 decay will be quickly degraded to GeV energies (in blazars and lower in MQs). Correlation between GeV and neutrino emissions is expected. (Also temporal changes in the -ray spectrum in the GLAST band during intense neutrino emission.)

23. Neutrino yields (in a km3 detector) TeV BLLac: < 0.03 event per year for Mrk 421, 501 during intense flares Blazars: ~ 1 event per year at Z~1 for the most powerful sources (e.g, 3C279). May be constrained further by GLAST. MQ: a few events from a powerful flare like the 1994 event seen in GRS 1915

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