Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION; MOLLERACH, SILVIA

Astrophysical Journal

Institute of Physics Publishinghelen.craven@iop.org

Año: 2018 vol. 868

We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4EeV measured using thePierre Auger Observatory. For the energy bins [4, 8]EeV and E 8 EeV, the most significant signal is a dipolarmodulation in R.A. at energies above 8EeV, as previously reported. In this paper we further scrutinize the highest-energybin by splitting it into three energy ranges. We find that the amplitude of the dipole increases with energy above 4EeV.The growth can be fitted with a power law with index β=0.79±0.19. The directions of the dipoles are consistent withan extragalactic origin of these anisotropies at all the energies considered. Additionally, we have estimated thequadrupolar components of the anisotropy: they are not statistically significant. We discuss the results in the context ofthe predictions from different models for the distribution of ultrahigh-energy sources and cosmic magnetic fields.