Scrutinizing FR 0 radio galaxies as ultra-high-energy cosmic ray source candidates

DOI: 
10.1016/j.astropartphys.2021.102564
Publication date: 
24/03/2021
Main author: 
Merten, Lukas
IAA authors: 
Bonnoli, Giacomo
Authors: 
Merten, Lukas;Boughelilba, Margot;Reimer, Anita;Da Vela, Paolo;Vorobiov, Serguei;Tavecchio, Fabrizio;Bonnoli, Giacomo;Lundquist, Jon Paul;Righi, Chiara
Journal: 
Astroparticle Physics
Publication type: 
Article
Volume: 
128
Pages: 
102564
Abstract: 
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 ∼10<SUP>20</SUP> eV. Based on this conjecture, the possibility of UHECR acceleration and survival in an FR 0 source environment is examined in this work. <P />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. <P />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 Γ<SUB>j</SUB> ≳ 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.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2021APh...12802564M/abstract
ADS Bibcode: 
2021APh...12802564M
Keywords: 
Acceleration of particles;Radiation mechanisms: nonthermal;Galaxies: jets;Galaxies: active;Cosmic rays;Astrophysics - High Energy Astrophysical Phenomena