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

THE PIERRE AUGER COLLABORATION, B. WUNDHEILER

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2018

0004-637X

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.