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arXiv · 1808.03579

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

The Pierre Auger Collaboration·A. Aab·P. Abreu·M. Aglietta·I. F. M. Albuquerque·J. M. Albury·I. Allekotte·A. Almela·J. Alvarez Castillo·J. Alvarez-Muñiz·G. A. Anastasi·L. Anchordoqui·B. Andrada·S. Andringa·C. Aramo·H. Asorey·P. Assis·G. Avila·A. M. Badescu·A. Balaceanu·F. Barbato·R. J. Barreira Luz·S. Baur·K. H. Becker·J. A. Bellido·C. Berat·M. E. Bertaina·X. Bertou·P. L. Biermann·J. Biteau·S. G. Blaess·A. Blanco·J. Blazek·C. Bleve·M. Boháčová·C. Bonifazi·N. Borodai·A. M. Botti·J. Brack·T. Bretz·A. Bridgeman·F. L. Briechle·P. Buchholz·A. Bueno·S. Buitink·M. Buscemi·K. S. Caballero-Mora·L. Caccianiga·L. Calcagni·A. Cancio·F. Canfora·J. M. Carceller·R. Caruso·A. Castellina·F. Catalani·G. Cataldi·L. Cazon·J. A. Chinellato·J. Chudoba·L. Chytka·R. W. Clay·A. C. Cobos Cerutti·R. Colalillo·A. Coleman·M. R. Coluccia·R. Conceição·G. Consolati·F. Contreras·M. J. Cooper·S. Coutu·C. E. Covault·B. Daniel·S. Dasso·K. Daumiller·B. R. Dawson·J. A. Day·R. M. de Almeida·S. J. de Jong·G. De Mauro·J. R. T. de Mello Neto·I. De Mitri·J. de Oliveira·V. de Souza·J. Debatin·O. Deligny·N. Dhital·M. L. Díaz Castro·F. Diogo·C. Dobrigkeit·J. C. D'Olivo·Q. Dorosti·R. C. dos Anjos·M. T. Dova·A. Dundovic·J. Ebr·R. Engel·M. Erdmann·C. O. Escobar·A. Etchegoyen·H. Falcke
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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 $E\geq 8$ EeV, the most significant signal is a dipolar modulation in right ascension 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 $\beta=0.79\pm 0.19$. 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.

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The Pierre Auger Collaboration, A. Aab, P. Abreu, M. Aglietta, I. F. M. Albuquerque, J. M. Albury, I. Allekotte, A. Almela, J. Alvarez Castillo, J. Alvarez-Muñiz, G. A. Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, H. Asorey, P. Assis, G. Avila, A. M. Badescu, A. Balaceanu, F. Barbato, R. J. Barreira Luz, S. Baur, K. H. Becker, J. A. Bellido, C. Berat, M. E. Bertaina, X. Bertou, P. L. Biermann, J. Biteau, S. G. Blaess, A. Blanco, J. Blazek, C. Bleve, M. Boháčová, C. Bonifazi, N. Borodai, A. M. Botti, J. Brack, T. Bretz, A. Bridgeman, F. L. Briechle, P. Buchholz, A. Bueno, S. Buitink, M. Buscemi, K. S. Caballero-Mora, L. Caccianiga, L. Calcagni, A. Cancio, F. Canfora, J. M. Carceller, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, R. Colalillo, A. Coleman, M. R. Coluccia, R. Conceição, G. Consolati, F. Contreras, M. J. Cooper, S. Coutu, C. E. Covault, B. Daniel, S. Dasso, K. Daumiller, B. R. Dawson, J. A. Day, R. M. de Almeida, S. J. de Jong, G. De Mauro, J. R. T. de Mello Neto, I. De Mitri, J. de Oliveira, V. de Souza, J. Debatin, O. Deligny, N. Dhital, M. L. Díaz Castro, F. Diogo, C. Dobrigkeit, J. C. D'Olivo, Q. Dorosti, R. C. dos Anjos, M. T. Dova, A. Dundovic, J. Ebr, R. Engel, M. Erdmann, C. O. Escobar, A. Etchegoyen, H. Falcke. 2018-08-10. Large-scale cosmic-ray anisotropies above 4 EeV measured by the Pierre Auger Observatory. https://doi.org/10.3847/1538-4357/aae689

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