On the excess of ultra-high energy cosmic rays in the direction of Centaurus A

Abstract

A posteriori anisotropy study of ultra-high energy cosmic rays (UHECRs) with the Pierre Auger Observatory (PAO) has shown evidence of excess of cosmic ray particles above 55 EeV within $18^{\circ }$ of the direction of the radio galaxy Centaurus A. However, the origin of the excess remains elusive. We simulate the propagation of different species of particles coming from the direction of Centaurus A in the Galactic magnetic fields, and find that only particles of nuclear charge $Z\la 10$ can avoid being deflected outside of the $18^{\circ }$ window of Centaurus A. On the other hand, considering the increasingly heavy composition of UHECRs at the highest energies measured by PAO, a plausible scenario for cosmic rays from the direction of Centaurus A can be found if they consist of intermediate-mass nuclei. The chemical composition of cosmic rays can be further constrained by lower-energy cosmic rays of the same rigidity. We find that cosmic ray acceleration in the lobes of Centaurus A is not favored, while acceleration in the stellar winds that are rich in intermediate-mass nuclei, could meet the requirement. This suggests that the observed excess may originate from cosmic ray accelerators induced by stellar explosions in the star-forming regions of Centaurus A and/or the Centaurus cluster located behind Centaurus A.

9 pages, 6 figures, 1 table; ApJ accepted

References in corpus (7)

• 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
• High-energy Cosmic Rays and Neutrinos from Semi-relativistic Hypernovae
• The Pierre Auger Observatory II: Studies of Cosmic Ray Composition and Hadronic Interaction models
• The Centaurus A Ultrahigh-Energy Cosmic Ray Excess and the Local Extragalactic Magnetic Field
• Sensitivity of Extensive Air Showers to Features of Hadronic Interactions at Ultra-High Energies
• A New Limit on the Distances of Nuclei UHECRs Sources

Cited by in corpus (8)

• Mass entrainment and turbulence-driven acceleration of ultra-high energy cosmic rays in Centaurus A
• A Case for Radio Galaxies as the Sources of IceCube's Astrophysical Neutrino Flux
• Constraints on the source of ultra-high energy cosmic rays using anisotropy vs chemical composition
• High-Energy Gamma Rays and Neutrinos from Nearby Radio Galaxies
• Interpreting correlated observations of cosmic rays and gamma-rays from Centaurus A with a proton blazar inspired model
• Probing UHECR production in Centaurus A using secondary neutrinos and gamma-rays
• Nearby active galactic nuclei and starburst galaxies as sources of the measured UHECRs anisotropy signal
• The origin of the very-high-energy radiation along the jet of Centaurus A