2021/02/01 by Lukas Merten, Margot Boughelilba, Anita Reimer +11
Physics and Astronomy · #Acceleration #Active galactic nucleus #Astrophysics #Astrophysics and Cosmic Phenomena #Cosmic ray #Fermi Gamma-ray Space Telescope #Flux (metallurgy) #Galaxy #Neutrino Physics Research #Particle acceleration #Physics #Radio Astronomy Observations and Technology #Radio galaxy #Ultra-high-energy cosmic ray #astro-ph.HE
paper · pdf · doi:10.1016/j.astropartphys.2021.102564
19 pages, 16 figures, 4 tables, accepted in Astroparticle Physics
arxiv created 2021/02/01 · openalex publication_date 2021/02/05 · arxiv updated 2021/03/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Fanaroff-Riley (FR) 0 radio galaxies compose a new class of radio galaxies, which are usually weaker but much more numerous than the well-established class of FR 1 and FR 2 galaxies. The latter classes have been proposed as sources of the ultra-high-energy cosmic rays (UHECRs) with energies reaching up to ∼1020 eV. Based on this conjecture, the possibility of UHECR acceleration and survival in an FR 0 source environment is examined in this work. In doing so, an average spectral energy distribution (SED) based on data from the FR 0 catalog (FR0CAT) is compiled. The resulting photon fields are used as targets for UHECRs, which suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. Multiple mechanisms are discussed to assess the UHECR acceleration probability, including Fermi-I order and gradual shear accelerations, and particle escape from the source region. This work shows that in a hybrid scenario, combining Fermi and shear accelerations, FR 0 galaxies can contribute to the observed UHECR flux, as long as Γj≳1.6, where shear acceleration starts to dominate over escape. Even in less optimistic scenarios, FR 0s can be expected to contribute to the cosmic-ray flux between the knee and the ankle. Our results are relatively robust with respect to the realized magnetic turbulence model and the speed of the accelerating shocks.