Constraining the sources of ultra-high-energy cosmic rays across and above the ankle with the spectrum and composition data measured at the Pierre Auger Observatory

Abdul Halim, A.Abreu, P.Aglietta, M.Allekotte, I.Almeida Cheminant, K.Almela, A.Alvarez-Muñiz, J.Ammerman Yebra, J.Anastasi, G.A.Anchordoqui, L.Andrada, B.Andringa, S.Aramo, C.Araújo Ferreira, P.R.Arnone, E.Arteaga Velázquez, J.C.Asorey, H.Assis, P.Avila, G.Avocone, E.et al.2023-09-202023-09-202023Journal of Cosmology and Astroparticle Physics, 2023; 2023(5):024-0-024-491475-75161475-7516https://hdl.handle.net/2440/139538Published May 10, 2023In this work we present the interpretation of the energy spectrum and mass composition data as measured by the Pierre Auger Collaboration above 6×10¹⁷ eV. We use an astrophysical model with two extragalactic source populations to model the hardening of the cosmic-ray flux at around 5×10¹⁸ eV (the so-called “ankle” feature) as a transition between these two components. We find our data to be well reproduced if sources above the ankle emit a mixed composition with a hard spectrum and a low rigidity cutoff. The component below the ankle is required to have a very soft spectrum and a mix of protons and intermediate-mass nuclei. The origin of this intermediate-mass component is not well constrained and it could originate from either Galactic or extragalactic sources. To the aim of evaluating our capability to constrain astrophysical models, we discuss the impact on the fit results of the main experimental systematic uncertainties and of the assumptions about quantities affecting the air shower development as well as the propagation and redshift distribution of injected ultra-high-energy cosmic rays (UHECRs).en© 2023 The Author(s). Published by IOP Publishing Ltd on behalf of Sissa Medialab. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.cosmic ray experimentscosmic ray theoryparticle accelerationultra high energy cosmic raysConstraining the sources of ultra-high-energy cosmic rays across and above the ankle with the spectrum and composition data measured at the Pierre Auger ObservatoryJournal article10.1088/1475-7516/2023/05/0242023-09-20627037Abdul Halim, A. [0000-0003-1218-1737]Bellido, J.A. [0000-0002-0833-9194]Clay, R.W. [0000-0002-9040-9648]Dawson, B.R. [0000-0002-4271-3055]Harvey, V. [0000-0001-9090-8415]Manning, B. [0000-0002-2715-4478]