Exploring Radio Galaxy Origin of Ultra-High Energy Cosmic Rays

Abstract

Exploring Radio Galaxy Origin of Ultra-High Energy Cosmic Rays

Dongsu Ryu^1, Hyesung Kang^2, Jeongbhin Seo^3

1Depart. of Physics, College of Natural Sciences, UNIST, Rep. of Korea 2Depart. of Earth Sciences, Pusan National University, Rep. of Korea 3Los Alamos National Laboratory, Los Alamos, USA

We study the scenario that relativistic jets from radio galaxies are the primary source of the ultra-high energy cosmic rays (UHECRs) observed on Earth. Employing a model energy spectrum derived from numerical simulations of FR I and II jets, characterized by a double power law and an extended exponential cutoff, we assess the energy spectrum and mass composition of UHECRs coming from both nearby radio galaxies and those distributed across the universe. Assuming that the jet of Virgo A is more relativistic than those of Centaurus A and Fornax A, we predict that UHECRs seen in the northern hemisphere would have a higher flux and a lighter composition than those seen in the southern hemisphere at the highest end of the UHECR energy spectrum. Our results may provide insights for the explanation of discrepancies in energy spectrum and mass composition between Telescope Array and Pierre Auger Observatory observations.