Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory
Adila Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, Kévin Almeida Cheminant, A. Almela, Roberto Aloisio, Jaime Álvarez-Muñiz, Juan Ammerman Yebra, Gioacchino Alex Anastasi, Luis A. Anchordoqui, Belén Andrada, S. Andringa, C. Aramo, Paulo Ricardo Araújo Ferreira, Enrico Arnone, Juan Carlos Arteaga Velázquez, H. Asorey, P. Assis, Gualberto Avila, Emanuele Avocone, Alina Mihaela Badescu, Alena Bakalová, A. Balaceanu, Felicia Barbato, Adriel Bartz Mocellin, Jose A. Bellido, Corinne Bérat, M. E. Bertaina, Gopal Bhatta, M. Bianciotto, Peter L. Biermann, Virginia Binet, Kathrin Bismark, Teresa Bister, Jonathan Biteau, Jiří Blažek, C. Bleve, J. Blümer, M. Boháčová, Denise Boncioli, C. Bonifazi, Luan Bonneau Arbeletche, Nataliia Borodai, J. Brack, P. Gabriel Brichetto Orchera, F. L. Briechle, A. Bueno, S. Buitink, Mario Buscemi, Max Büsken, Anthony Bwembya, K. S. Caballero‐Mora, Lorenzo Caccianiga, Ioana Caracas, R. Caruso, A. Castellina, Fernando Catalani, G. Cataldi, Lorenzo Cazon, M. Cerda, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, Agustín Cobos Cerutti, Roberta Colalillo, Alan Coleman, M. R. Coluccia, R. Conceição, Antonio Condorelli, Giovanni Consolati, M. Conte, Fabio Convenga, Diego Correia dos Santos, Paulo J. Costa, C. E. Covault, M. Cristinziani, Carlo Salvattore Cruz Sanchez, S. Dasso, K. Daumiller, B. R. Dawson, R. M. de Almeida, J. de Jesús, S. J. de Jong, J.R.T. de Mello Neto, I. De Mitri, Jaime de Oliveira, Danelise de Oliveira Franco, F. de Palma, V. de Souza, Emanuele De Vito, Antonino Del Popolo, Olivier Deligny, L. Deval, Armando di Matteo, M. Dobre, C. Dobrigkeit, J. C. D’Olivo, Luis Miguel Domingues Mendes
Abstract
Abstract The combined fit of the measured energy spectrum and shower maximum depth distributions of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical models with homogeneous source distributions. Studies of the distribution of the cosmic-ray arrival directions show a better agreement with models in which a fraction of the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with catalogs such as that of starburst galaxies. Here, we present a novel combination of both analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data measured at the Pierre Auger Observatory. The model takes into account a rigidity-dependent magnetic field blurring and an energy-dependent evolution of the catalog contribution shaped by interactions during propagation. We find that a model containing a flux contribution from the starburst galaxy catalog of around 20% at 40 EeV with a magnetic field blurring of around 20° for a rigidity of 10 EV provides a fair simultaneous description of all three observables. The starburst galaxy model is favored with a significance of 4.5σ (considering experimental systematic effects) compared to a reference model with only homogeneously distributed background sources. By investigating a scenario with Centaurus A as a single source in combination with the homogeneous background, we confirm that this region of the sky provides the dominant contribution to the observed anisotropy signal. Models containing a catalog of jetted active galactic nuclei whose flux scales with the γ-ray emission are, however, disfavored as they cannot adequately describe the measured arrival directions.