A correlation between the highest energy cosmic rays and nearby active galactic nuclei detected by Fermi

Abstract

We analyze the correlation of the positions of γ -ray sources in the Fermi Large Area Telescope (LAT) First Source Catalog (1FGL) and the First LAT Active Galactic Nuclei (AGNs) Catalog (1LAC) with the arrival directions of ultra-high-energy cosmic rays (UHECRs) observed with the Pierre Auger Observatory, in order to investigate the origin of UHECRs.We find that Galactic sources and blazars identified in the 1FGL are not significantly correlated with UHECRs, while the 1LAC sources display a mild correlation (2.6σ level) on an ≈2°.4 angular scale. When selecting only the 1LAC AGNs closer than 200 Mpc, we find a strong association (5.4σ) between their positions and the directions of UHECRs on an ≈17°. angular scale; the probability of the observed configuration being due to an isotropic flux of cosmic rays is 5×10−8. There is also a 5σ correlation with nearby 1LAC sources on a 6°.5 scale.We identify seven “γ -ray loud” AGNs which are associated with UHECRs within ≈17°. and are likely candidates for the production sites of UHECRs: Centaurus A, NGC 4945, ESO 323−G77, 4C+04.77, NGC 1218, RX J0008.0+1450, and NGC 253.We interpret these results as providing additional support to the hypothesis of the origin of UHECRs in nearby extragalactic objects. As the angular scales of the correlations are large, we discuss the possibility that intervening magnetic fields might be considerably deflecting the trajectories of the particles on their way to Earth.