Ultra-high-energy cosmic rays from centaurus A: Jet interaction with gaseous shells

Gopal-Krishna, ; Biermann, Peter L. ; Souza, Vitor de ; Wiita, Paul J. (2010) Ultra-high-energy cosmic rays from centaurus A: Jet interaction with gaseous shells The Astrophysical Journal Letters, 720 (2). L155 - L1558. ISSN 0571-7248

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Official URL: http://iopscience.iop.org/2041-8205/720/2/L155

Related URL: http://dx.doi.org/10.1088/2041-8205/720/2/L155


Ultra-high-energy cosmic rays (UHECRs), with energies above ~6 × 1019 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.

Item Type:Article
Source:Copyright of this article belongs to IOP Science.
Keywords:Acceleration of Particles; Galaxies: Individual (Cen A); Galaxies: ISM; Galaxies: Jets; Radio Continuum: Galaxies
ID Code:76589
Deposited On:04 Jan 2012 07:18
Last Modified:06 Jan 2012 03:42

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