Ultra-High Energy Cosmic Rays from Centaurus A: Jet Interaction with Gaseous Shells

Abstract

Ultra high energy cosmic rays (UHECRs), with energies above ~6 x 10^19 eV, seem to show a weak correlation with the distribution of matter relatively near to us in the universe. It has earlier been proposed that UHECRs could be accelerated in either the nucleus or the outer lobes of the nearby radio galaxy Cen A. We show that UHECR production at a spatially intermediate location about 15 kpc northeast from the nucleus, where the jet emerging from the nucleus is observed to strike a large star-forming shell of gas, is a plausible alternative. A relativistic jet is capable of accelerating lower-energy heavy seed cosmic rays (CRs) to UHECRs on timescales comparable to the time it takes the jet to pierce the large gaseous cloud. In this model many CRs arising from a starburst, with a composition enhanced in heavy elements near the knee region around PeV, are boosted to ultra-high energies by the relativistic shock of a newly oriented jet. This model matches the overall spectrum shown by the Auger data and also makes a prediction for the chemical composition as a function of particle energy. We thus predict an observable anisotropy in the composition at high energy in the sense that lighter nuclei should preferentially be seen toward the general direction of Cen A. Taking into consideration the magnetic field models for the Galactic disk and a Galactic magnetic wind, this scenario may resolve the discrepancy between HiRes and Auger results concerning the chemical composition of UHECRs.

11 pages, 1 figure, in press in Astrophysical Journal Letters

References in corpus (9)

• Turbulence and Magnetic Fields in the Large Scale Structure of the Universe
• Fermi Gamma-ray Imaging of a Radio Galaxy
• Search for Correlations between HiRes Stereo Events and Active Galactic Nuclei
• The spin-flip phenomenon in supermassive black hole binary mergers
• Propagation of UHE Protons through Magnetized Cosmic Web
• Cosmic ray electrons and positrons from supernova explosions of massive stars
• Hydrodynamic Interactions of Relativistic Extragalactic Jets with Dense Clouds
• Active Galactic Nuclei: Sources for ultra high energy cosmic rays?
• Cosmic Rays X. The cosmic ray knee and beyond: Diffusive acceleration at oblique shocks

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