Gamma-rays from snrs and cosmic rays V. N. Zirakashvili


НазваGamma-rays from snrs and cosmic rays V. N. Zirakashvili
Дата конвертації26.04.2013
Розмір477 b.
ТипПрезентации


Gamma-rays from SNRs and cosmic rays

  • V.N.Zirakashvili


Outline

  • Acceleration of particles at forward and reverse shocks in SNRs

  • Amplification of magnetic fields

  • Radioactivity and electron acceleration

  • Modeling of DSA in SNRs

  • Modeling of broad-band emission



Diffusive Shock Acceleration



Shock modification by the pressure of accelerated CRs.

  • Axford 1977, 1981

  • Eichler 1984

  • Higher compression ratio of the shock, concave spectrum of particles.



X-ray image of Tycho SNR (from Warren et al. 2005)

  • 1. CD is close to the forward shock – evidence of the shock modification by CR pressure.

  • 2. Thin non-thermal X-ray filaments at the periphery of the remnant – evidence of electron acceleration and of magnetic amplification.



Magnetic field amplification by non-resonant streaming instability







Schematic picture of the fast shock with accelerated particles



CR acceleration at the reverse shock (e.g.Ellison et al. 2005) ? Probably presents in Cas A (Helder & Vink 2008)







Radioactivity and electron acceleration in SNRs (Zirakashvili & Aharonian (2011))



“Radioactive” scenario in the youngest galactic SNR G1.9+0.3



Numerical model of nonlinear diffusive shock acceleration (Zirakashvili & Ptuskin 2011) (natural development of existing models of Berezhko et al. (1994-2006), Kang & Jones 2006, see also half-analytical models of Blasi et al.(2005); Ellison et al. (2010) )



Numerical results



Radial profiles at T=1000 years



Spectra of accelerated particles



Integrated spectra



Integrated spectra



Evolution of nonthermal emission from SNR



TeV gamma-rays from young SNRs



Fermi LAT results on RX J1713.7-3946 (Abdo et al. 2011)



Vela Jr.:Fermi results (Tanaka et al. 2011)



Modeling of broad-band spectra of Cas A for the “radioactive” scenario of lepton injection (Zirakashvili et al. 2012 in preparation)



Broad-band modeling of Tycho SNR (Morlino & Caprioli 2011)



Old SNRs (T>104 yr)



Summary

  • Non-resonant streaming instability produced by the electric current of run-away CR particles results in the significant magnetic amplification at fast SNR shocks.

  • 2. The reverse shocks in SNRs can produce CR ions and positrons with spectrum that is harder in comparison with spectra of particles accelerated at the forward shock.

  • 3. Both leptonic and hadronic origin of gamma-emission in SNRs RX J1713.7-3946, Vela Junior, Cas A are possible.

  • 4. SNR Tycho and old SNRs are good candidates for a hadronic origin of gamma-emission.



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