Active Galactic Nuclei as High Energy Engines

Abstract

Active Galactic Nuclei are considered as possible sites of cosmic ray acceleration and some of them have been observed as high energy gamma ray emitters (Blazars). There naturally comes an appealing idea that the acceleration of the highest energy cosmic rays in the AGNs has a signature in the form of gamma ray emission and high energy neutrino emission through the collisions of very high energy protons with soft photons. Moreover it is often said that electrons cannot reach enough energy through Fermi acceleration to account for the highest energy photons observed with ground Cerenkov telescopes. In this paper, we discussed these points and show that the fast variability of the flares recently observed rules out the assumption of a Fermi acceleration of protons. We show that Fermi acceleration of electrons is enough to account for the gamma spectra, their shape, cut-off and their variability. Moreover the spectral break is nicely explained by invoking an gamma-ray photosphere. Nevertheless we give estimates of the high energy cosmic ray generation in AGNs and of the resultant neutrino flux, that turns out to be very sensitive to the spectral index of the proton distribution.

17 pages, 1 figure, accepted for publication in Astrophysics Particles

References in corpus (3)

• BeppoSAX Observations of Unprecedented Synchrotron Activity in the BL Lac Object Mkn 501
• Absorption of High Energy Gamma Rays by Interactions With Starlight Photons in Extragalactic Space at High Redshifts and the High Energy Gamma-Ray Background
• The terminal bulk Lorentz factor of relativistic electron-positron jets

Cited by in corpus (20)

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• The Astrophysics of Ultrahigh Energy Cosmic Rays
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• Superbubbles and Energetic Particles in the Galaxy. I: Collective effects of particle acceleration
• Proton synchrotron radiation of large-scale jets in active galactic nuclei
• Anisotropy vs chemical composition at ultra-high energies
• Simultaneous Multiwavelength observation of Mkn 501 in a low state in 2006
• The environment and distribution of emitting electrons as a function of source activity in Markarian 421
• Cosmic Ray Acceleration by a Versatile Family of Galactic Wind Termination Shocks
• Acceleration and propagation of ultrahigh energy cosmic rays
• Possible Proton Synchrotron Origin of X-Ray & Gamma Ray Emission in Large Scale Jet of 3C 273
• Constraining Sources of Ultra High Energy Cosmic Rays Using High Energy Observations with the Fermi Satellite
• Constraints on Proton Synchrotron Origin of Very High Energy Gamma Rays from the Extended Jet of AP Librae
• New prototype scintillator detector for the Tibet AS$\gamma$ Experiment
• Hard TeV Gamma-Ray Afterglows of Nearby GRB 190829A as a Tentative Signature of Ultra-High-Energy Cosmic Rays Accelerated in Gamma-Ray Burst Jets
• Ultra high energy cosmic rays and possible signature of black strings
• Luminosity of ultrahigh energy cosmic rays and bounds on magnetic luminosity of radio-loud active galactic nuclei
• Pair Creation at Shocks: Application to the High Energy Emission of Compact objects
• The new model of fitting the spectral energy distributions of Mkn 421 and Mkn 501