We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4EeV measured 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 R.A. at energies above 8EeV, as previously reported. In this paper we further scrutinize the highest-energy bin 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 with an extragalactic origin of these anisotropies at all the energies considered. Additionally, we have 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 of ultrahigh-energy sources and cosmic magnetic fields.

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

Caruso, R.;Insolia, A.;Presti, D. Lo;Perrone, L.;Pirronello, V.;Salina, G.;Zuccarello, F.
2018

Abstract

We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4EeV measured 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 R.A. at energies above 8EeV, as previously reported. In this paper we further scrutinize the highest-energy bin 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 with an extragalactic origin of these anisotropies at all the energies considered. Additionally, we have 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 of ultrahigh-energy sources and cosmic magnetic fields.
large scale anysotropy, extragalactic origin
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/357764
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