Correlation between Cosmic Rays and their Source

Science 9 November 2007:
Vol. 318. no. 5852, pp. 938 - 943
DOI: 10.1126/science.1151124


Research Articles
Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects The Pierre Auger Collaboration*

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10¹⁹ electron volts and the positions of active galactic nuclei (AGN) lying within ~75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.