Ultrahigh energy cosmic ray acceleration in Seyfert galactic nuclei

Abstract

We perform Monte Carlo simulations of transrelativistic shear acceleration dedicated to a jet-cocoon system of active galactic nuclei. A certain fraction of galactic cosmic rays in a halo is entrained, and sufficiently high-energy particles can be injected to the reacceleration process and further accelerated up to 100 EeV. We show that the shear reacceleration mechanism leads to a hard spectrum of escaping cosmic rays, dLE/dE ∝ E −1 − E 0 , distinct from a conventional E −2 spectrum. The supersolar abundance of ultrahigh-energy nuclei is achieved due to injections at TeV-PeV energies. As a result, we find that the highest-energy spectrum and mass composition can be reasonably explained by our model without contradictions with the anisotropy data.

Spectra and mass composition of ultrahigh-energy cosmic rays from point sources

“…Differential energy spectra of some abundant nuclei (p,4 He,16 O, 56 Fe) at a source, with γ 0 = 2.6 (the left panel) and γ 0 = 4.6 (the right panel). The total spectrum (solid thick curve) is normalized to unity at E = 5·10 19 eV.…”

The maximum energy and spectra of cosmic rays accelerated in active galactic nuclei

“…accelerated at shock fronts [7], we assume that the initial spectrum of the particles from them is a power law (~E -χ ) with a spectral index of ? = 2.6 and 3.0.…”

Possible origin of clusters in ultra-high-energy cosmic rays

“…This estimate was obtained by assuming that the particles are emitted by the source isotropically. However, in our acceleration model [8,12], the particles are accelerated in a jet and are emitted in a directed beam with an opening half-angle of θ ≤ 6.5 × 10 −4 . Taking into account the possible conversion of the accelerated particles from the charged into the neutral state and back [15], we find that UHECRs are emitted in a cone with an angle of 20 0 .…”

“…When identifying the sources, we assumed that CRs are deflected by the intergalactic magnetic fields through no more than 9 0 . The intergalactic magnetic fields are B < 10 −9 G [7], and this condition is satisfied for the particles arrived from distances of ∼ 50 Mpc, i.e., emitted by Seyfert nuclei with z < 0.01 [8]. BL Lac objects are hundreds of megaparsecs away, but even for such distant sources, the deflections may not exceed a few degrees if the filamentary structure of the intergalactic magnetic fields is taken into account [9].…”

“…The particle acceleration in the identified objects was considered in [8,[10][11][12]. It was shown that conditions for particle acceleration to energies of 10 21 eV exist in the identified objects.…”