Large-scale cosmic-ray anisotropies above 4 EeV measured by the Pierre Auger Observatory

H. WAHLBERG Y PIERRE AUGER COLLABORATION

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 EeVmeasured using the Pierre Auger Observatory. For the energy bins [4, 8] EeV and E ≥ 8 EeV, the most significant signal is a dipolar modulation in right ascension at energies above 8 EeV, as previouslyreported. In this paper we further scrutinize the highest-energy bin by splitting it into three energyranges. We find that the amplitude of the dipole increases with energy above 4 EeV. The growth canbe fitted with a power law with index β = 0.79 ± 0.19. The directions of the dipoles are consistentwith an extragalactic origin of these anisotropies at all the energies considered. Additionally wehave estimated the quadrupolar components of the anisotropy: they are not statistically significant.We discuss the results in the context of the predictions from different models for the distribution ofultrahigh-energy sources and cosmic magnetic fields.