High Energy Cosmic Rays from Fanaroff-Riley Radio Galaxies

Abstract

The extended jet structures of radio galaxies (RGs) represent an ideal acceleration site for High Energy Cosmic Rays (HECRs) and a recent model showed that the HECR data can be explained by these sources, if the arrival directions of HECRs at energies $\lesssim 8\text{EeV}$ from a certain RG, Cygnus A, are isotropized. First, this work introduces the inverted simulation setup in order to probe the isotropy assumption. Here, different extragalactic magnetic field models are compared showing that either a magnetic field of primordial origin that yields a high field strength in the large scale structures of the Universe is needed, or a significant contribution by a multitude of isotropically distributed sources. Secondly, the HECRs contribution by the bulk of RGs of different Fanaroff-Riley (FR) type is determined. Here, the most recent FR-type dependent radio-to-CR correlations $Q_{\mathrm{cr}}\propto L_{\mathrm{radio}}^{{\beta }_L}$ are used, and the impact of the slope ${\beta }_L$ on the HECRs is analyzed in detail. Finally, it is carved out that FR-II RGs provide a promising spectral behavior at the hardening part of the CR flux, between about $3\text{EeV}$ and $30\text{EeV}$, but most likely not enough CR power. At these energies, FR-I RGs can only provide an appropriate flux in the case of a high acceleration efficiency and ${\beta }_L\gtrsim 0.9$, otherwise these sources rather contribute below $3\text{EeV}$. Further, the required acceleration efficiency for a significant HECR contribution is exposed dependent on ${\beta }_L$ and the CR spectrum at the acceleration site.

References in corpus (11)

• The NumPy array: a structure for efficient numerical computation
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above $8\times 10^{18}$ eV
• Radio sources in the 6dFGS: Local luminosity functions at 1.4 GHz for star-forming galaxies and radio-loud AGN
• Radio galaxies of the local universe: all-sky catalog, luminosity functions, and clustering
• Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition
• Simulations of ultra-high Energy Cosmic Rays in the local Universe and the origin of Cosmic Magnetic Fields
• Cosmic ray diffusion near the Bohm limit in the Cassiopeia A supernova remnant
• High redshift FRII radio sources: large-scale X-ray environment
• Cosmic Rays: The Second Knee and Beyond
• Cosmic Ray Acceleration by Relativistic Shocks: Limits and Estimates

Cited by in corpus (2)

• CRPropa 3.2 -- an advanced framework for high-energy particle propagation in extragalactic and galactic spaces
• Magnetically Induced Anisotropies in the Arrival Directions of Ultra-high-energy Cosmic Rays from Nearby Radio Galaxies