Large Scale Distribution of Arrival Directions of Cosmic Rays Detected about 10(18) eV at the Pierre Auger Observatory.

摘要

A thorough search for large scale anisotropies in the distribution of arrival directions of cosmic rays detected above 10(18) eV at the Pierre Auger Observatory is presented. This search is performed in several energy ranges in terms of dipoles and quadrupoles as a function of both the declination and the right ascension. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Assuming that the eventual anisotropic component of the angular distribution of cosmic rays is dominated by dipole and quadrupole moments in this energy range, upper limits on dipole and quadrupole amplitudes are derived. These upper limits allow us to challenge an origin of cosmic rays above 10(18) eV from stationary galactic sources densely distributed in the galactic disk and emitting predominantly light particles in all directions.