Astroparticle yield and transport from extragalactic jet terminal shocks

作者：Casse F; Marcowith A^*

来源：Astroparticle Physics, 2005, 23(1): 31-56.

DOI：10.1016/j.astropartphys.2004.11.003

• particle acceleration
• active galactic nuclei
• hot-spots
• kinetic theory
• MHD
• cosmic rays
• high-energy neutrinos
• photons (X and -y)
• synchrotron radiation

The present paper deals with the yield and transport of high-energy particle within extragalactic jet terminal shocks, also known as hot-spots. These astrophysical sources are responsible for strong non-thermal synchrotron emission produced by relativistic electrons accelerated via a Fermi-type mechanism. We investigate in some details the cosmic ray. neutrinos and high-energy photons yield in hot-spots of powerful FRII radio-galaxies by scanning all known spatial transport regimes, adiabatic and radiative losses as well as Fermi acceleration process. Since both electrons and cosmic rays are prone to the same type of acceleration, we derive analytical estimates of the maximal cosmic ray energy attainable in both toroidal and poloidal magnetic field dominated shock structures by using observational data on synchrotron emission coming from various hot-spots. One of our main conclusions is that the best hot-spot candidates for high energy astroparticle production is the extended (L-HS greater than or equal to l kpc), strongly magnetized (B > 0.1 mG) terminal shock displaying synchrotron emission cut-off lying at least in the optical band. We found only one object (3C273 A) over the six objects in our sample being capable to produce cosmic rays up to 10(20) eV. We also show that the Bohm regime is unlikely to occur in the whole hot-spot since it would require unrealistically low jet velocities. Secondly, we investigate the astroparticle spectra produced by two characteristic hot-spots (Cygnus A and 3C273 A) by applying a multi-scale MHD-kinetic scheme, coupling MHD simulations to kinetic computations using stochastic differential equations. We show that 3C273 A, matching the previous properties, may produce protons up to 10(20)eV in a Kolmogorov-type turbulence by both computing electron and cosmic ray acceleration. We also calculate the high-energy neutrino and Gamma-ray fluxes on Earth produced through p-gamma and p-p processes and compare them to the most sensitive astroparticle experiments.

• 出版日期2005-2