Correlation of the Highest-Energy Cosmic Rays with Nearby Active Galactic Nuclei.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

ASTROPARTICLE PHYSICS

Año: 2007

0927-6505

Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [1]. The correlation has maximum signi cance for cosmic rays with energy greater than  61019 eV and AGN at a distance less than  75 Mpc. We have con rmed the anisotropy at a con dence level of more than 99% through a test with parameters speci ed a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their ux is not signi cantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuz'min eect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic elds are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identi - cation of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.61019 eV and AGN at a distance less than  75 Mpc. We have con rmed the anisotropy at a con dence level of more than 99% through a test with parameters speci ed a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their ux is not signi cantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuz'min eect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic elds are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identi - cation of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their ux is not signi cantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuz'min eect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic elds are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identi - cation of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.