On the interpretation of the cosmic-ray anisotropy at ultra-high energies

TL;DR

This paper critically examines the AGN hypothesis for ultra-high-energy cosmic-ray origins, showing discrepancies between expected and observed arrival directions, and explores alternative sources like Cen A.

Contribution

It provides a detailed calculation of expected cosmic-ray arrival directions under the AGN hypothesis and compares it with observational data, challenging the prevailing interpretation.

Findings

Discrepancy between predicted and observed cosmic-ray directions

Deficit of events from Virgo supercluster direction

Potential significance of Cen A as a source

Abstract

A natural interpretation of the correlation between nearby Active Galactic Nuclei (AGN) and the highest-energy cosmic rays observed recently by the Pierre Auger Collaboration is that the sources of the cosmic rays are either AGN or other objects with a similar spatial distribution (the ``AGN hypothesis''). We question this interpretation. We calculate the expected distribution of the arrival directions of cosmic rays under the AGN hypothesis and argue that it is not supported by the data, one of manifestations of the discrepancy being the deficit of events from the direction of the Virgo supercluster. We briefly discuss possible alternative explanations including the origin of a significant part of the observed events from Cen A.