Centaurus A: the one extragalactic source of cosmic rays with energies above the knee

Abstract

The origin of cosmic rays at all energies is still uncertain. In this paper we present and explore an astrophysical scenario to produce cosmic rays with energy ranging from below $10^{15}$ o $3 \times 10^{20}$ eV. We show here that just our Galaxy and the radio galaxy Cen A, each with their own galactic cosmic ray particles, but with those from the radio galaxy pushed up in energy by a relativistic shock in the jet emanating from the active black hole, are sufficient to describe the most recent data in the energy range PeV to near ZeV. Data are available over this entire energy range from the experiments KASCADE, KASCADE-Grande and Pierre Auger Observatory. The energy spectrum calculated here correctly reproduces the measured spectrum beyond the knee, and contrary to widely held expectations, no other extragalactic source population is required to explain the data, even at energies far below the general cutoff expected at $6 \times 10^{19}$ eV, the Greisen-Zatsepin-Kuzmin turn-off due to interaction with the cosmological microwave background. We present several predictions for the source population, the cosmic ray composition and the propagation to Earth which can be tested in the near future.