Ultra-High-Energy Cosmic Rays from the Radio Lobes of AGNs

Abstract

In the past year, the HiRes and Auger collaborations have reported the discovery of a high-energy cutoff in the ultra-high energy cosmic-ray (UHECR) spectrum, and an apparent clustering of the highest energy events towards nearby active galactic nuclei (AGNs). Consensus is building that such $\sim 10^{19}$--$10^{20}$ eV particles are accelerated within the radio-bright lobes of these sources, but it is not yet clear how this actually happens. In this paper, we report (to our knowledge) the first treatment of stochastic particle acceleration in such environments from first principles, showing that energies $\sim 10^{20}$ eV are reached in $\sim 10^6$ years for protons. However, our findings reopen the question regarding whether the high-energy cutoff is due solely to propagation effects, or whether it does in fact represent the maximum energy permitted by the acceleration process itself.

arXiv comment8 pages, 7 figures, acccepted for publication in MNRAS

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• High-energy Particle Acceleration and Production of Ultra-high-energy Cosmic Rays in the Giant Lobes of Centaurus A
• Ultra High Energy Cosmic Rays from Black Hole Jets of Radio Galaxies
• Fermi gamma-ray `bubbles' from stochastic acceleration of electrons
• Stochastic particle acceleration in the lobes of giant radio galaxies
• Faraday Rotation Structure on Kiloparsec Scales in the Giant Radio Lobes of Centaurus A
• Ultra-High Energy Cosmic Ray production in the polar cap regions of black hole magnetospheres
• Neutrino diagnostics of ultra-high energy cosmic ray protons
• Fornax A, Centaurus A and other radio galaxies as sources of ultra-high energy cosmic rays
• Test-particle acceleration in a hierarchical three-dimensional turbulence model
• Decoding the giant extragalactic radio sources
• High Energy Cosmic-ray Diffusion in Molecular Clouds: A Numerical Approach
• The Centaurus A Ultrahigh-Energy Cosmic Ray Excess and the Local Extragalactic Magnetic Field
• Early-time velocity autocorrelation for charged particles diffusion and drift in static magnetic turbulence
• Propagation of Ultra-High-Energy Cosmic Ray Nuclei in Cosmic Magnetic Fields and Implications for Anisotropy Measurements
• Non-thermal transient sources from rotating black holes
• Diffusive Cosmic Ray Acceleration at the Galactic Centre
• A Numerical Assessment of Cosmic-ray Energy Diffusion through Turbulent Media
• Additional Acceleration of Protons and Energetic Neutrino Production in a Filamentary Jet of the Blazar Markarian 501
• On Estimating the Flux of the Brightest Cosmic Ray Source above 57x10^18 eV
• 2nd-order Fermi acceleration as the origin of the Fermi bubbles