Correlations with nearby AGN measured by the Pierre Auger Observatory

ESTEBAN ROULET, FOR THE PIERRE AUGER COLLABORATION

Malfa, Italia

Congreso; CRIS 08; 2008

We discuss the recent results of the Pierre Auger Observatory showing a correlation between the highest energy cosmic rays  and  the nearby  extragalactic matter distribution. This was established from a comparison of the arrival directions detected and the positions of the known AGNs. By performing a scan over the maximum angular separation, the maximum AGN redshift and the threshold energy considered, the largest significance was obtained for angles of 3.2$^circ$, distances of 71~Mpc and energies above 57~EeV, for which 20 events out of 27 are found to be in correlation, while on average only 5.6 were expected to be correlated by chance if the distribution was isotropic. In general the correlation is significant for angles smaller than 6$^circ$ and distances up to 100~Mpc. This indicates that the highest energy cosmic rays are  extragalactic and supports the conclusion that the observed suppression in the cosmic ray spectrum at the highest energies is indeed due to the GZK effect rather than to the exhaustion of the acceleration power of the sources.