Anisotropy and chemical composition of ultra-high energy cosmic rays using the arrival directions measured by the Pierre Auger Observatory.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS

IOP PUBLISHING LTD

Lugar: Londres; Año: 2011 vol. 6 p. 22 - 30

1475-7516

The Pierre Auger Collaboration has reported evidence for anisotropy in the dis-tribution of arrival directions of the cosmic rays with energies E > Eth = 5.5×1019 eV. Theseshow a correlation with the distribution of nearby extragalactic objects, including an appar-ent excess around the direction of Centaurus A. If the particles responsible for these excessesat E > Eth are heavy nuclei with charge Z, the proton component of the sources should leadto excesses in the same regions at energies E/Z. We here report the lack of anisotropies inthese directions at energies above Eth/Z (for illustrative values of Z = 6, 13, 26). If theanisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptionsabout the acceleration process, these observations imply stringent constraints on the allowedproton fraction at the lower energies.