Document Type
Article
Publication Date
11-20-2018
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.
Publication Source (Journal or Book title)
Astrophysical Journal
Recommended Citation
Aab, A., Abreu, P., Aglietta, M., Albuquerque, I., Albury, J., Allekotte, I., Almela, A., Castillo, J., Alvarez-Muñiz, J., Anastasi, G., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Asorey, H., Assis, P., Avila, G., Badescu, A., Balaceanu, A., Barbato, F., Luz, R., Baur, S., Becker, K., Bellido, J., Berat, C., Bertaina, M., Bertou, X., Biermann, P., Biteau, J., Blaess, S., Blanco, A., Blazek, J., & Bleve, C. (2018). Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory. Astrophysical Journal, 868 (1) https://doi.org/10.3847/1538-4357/aae689