Arrival Directions of Cosmic Rays above 32 EeV from Phase One of the Pierre Auger Observatory
P. Abreu, M. Aglietta, Justin M. Albury, I. Allekotte, Kévin Almeida Cheminant, A. Almela, Jaime Álvarez-Muñiz, Rafael Alves Batista, Juan Ammerman Yebra, Gioacchino Alex Anastasi, Luis A. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, Paulo Ricardo Araújo Ferreira, Enrico Arnone, Juan Carlos Arteaga Velázquez, H. Asorey, P. Assis, Gualberto Avila, Emanuele Avocone, A. M. Badescu, Alena Bakalová, Alexandru Balaceanu, Felicia Barbato, Jose A. Bellido, Corinne Bérat, М. Бертаина, Gopal Bhatta, Peter L. Biermann, Virginia Binet, Kathrin Bismark, Teresa Bister, J. Biteau, Jiří Blažek, C. Bleve, J. Blümer, M. Boháčová, Denise Boncioli, C. Bonifazi, Luan Bonneau Arbeletche, Nataliia Borodai, Ana Martina Botti, J. Brack, T. Bretz, P. Gabriel Brichetto Orchera, F. L. Briechle, P. Buchholz, A. Bueno, S. Buitink, Mario Buscemi, M. Büsken, K. S. Caballero‐Mora, Lorenzo Caccianiga, F. Canfora, Ioana Caracas, R. Caruso, A. Castellina, Fernando Catalani, G. Cataldi, Lorenzo Cazon, M. Cerda, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, Roberta Colalillo, Alan Coleman, M.R. Coluccia, R. Conceição, Antonio Condorelli, Giovanni Consolati, F. Contreras, Fabio Convenga, D. Correia dos Santos, C. E. Covault, S. Dasso, K. Daumiller, B. R. Dawson, J. A. Day, R. M. de Almeida, Joaquín de Jesús, S. J. de Jong, A. De Roeck, I. De Mitri, J. de Oliveira, Danelise de Oliveira Franco, F. de Palma, V. de Souza, Emanuele De Vito, Antonino Del Popolo, Mariano del Río, Olivier Deligny, L. Deval, Armando di Matteo, M. Dobre, C. Dobrigkeit, Juan Carlos D’Olivo, Luis Miguel Domingues Mendes
Abstract
Abstract A promising energy range to look for angular correlations between cosmic rays of extragalactic origin and their sources is at the highest energies, above a few tens of EeV (1 EeV ≡ 10 18 eV). Despite the flux of these particles being extremely low, the area of ∼3000 km 2 covered at the Pierre Auger Observatory, and the 17 yr data-taking period of the Phase 1 of its operations, have enabled us to measure the arrival directions of more than 2600 ultra-high-energy cosmic rays above 32 EeV. We publish this data set, the largest available at such energies from an integrated exposure of 122,000 km 2 sr yr, and search it for anisotropies over the 3.4 π steradians covered with the Observatory. Evidence for a deviation in excess of isotropy at intermediate angular scales, with ∼15° Gaussian spread or ∼25° top-hat radius, is obtained at the 4 σ significance level for cosmic-ray energies above ∼40 EeV.