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

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)

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

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

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

Source AGNMQGRB parameter

External radiation field

Intrinsic synchrotron intensity

Energy scales Threshold energies for interaction with peak synchrotron photons 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.

Source AGNMQGRB energy observed rest frame Various energy scales

Electromagnetic emission

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

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 r(cm) r0r MQ AGN

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

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

Hadronic emission

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

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

Relations between photo-  production and  γ pair-production Same target photons for both processes.

Opacity ratio (target: synchrotron photons)    GeV  GeV  TeV  TeV Mrk 421

Opacity ratio (target: external radiation field)    GeV    GeV    TeV    TeV

Regions of significant photo-  opacity are opaque to emission of VHE gamma rays. Highly variable VHE  -ray sources, in particular TeV blazars are not good candidates for km 3 neutrino detectors. In regions of high photo-  opacity,  - rays produced through π 0 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.) Conclusions

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

THE END