https://doi.org/10.1140/epjc/s10052-021-08885-4
Regular Article - Theoretical Physics
Modeling the spectrum and composition of ultrahigh-energy cosmic rays with two populations of extragalactic sources
1
Astronomy and Astrophysics Group, Raman Research Institute, 560080, Bengaluru, India
2
Centre for Astro-Particle Physics (CAPP) and Department of Physics, University of Johannesburg, PO Box 524, 2006, Auckland Park, South Africa
Received:
3
December
2020
Accepted:
13
January
2021
Published online:
20
January
2021
We fit the ultrahigh-energy cosmic-ray (UHECR, 
EeV) spectrum and composition data from the Pierre Auger Observatory at energies 
eV, i.e., beyond the ankle using two populations of astrophysical sources. One population, accelerating dominantly protons (
H), extends up to the highest observed energies with maximum energy close to the GZK cutoff and injection spectral index near the Fermi acceleration model; while another population accelerates light-to-heavy nuclei (
He, 
N, 
Si, 
Fe) with a relatively low rigidity cutoff and hard injection spectrum. A significant improvement in the combined fit is noted as we go from a one-population to two-population model. For the latter, we constrain the maximum allowed proton fraction at the highest-energy bin within 3.5
statistical significance. In the single-population model, low-luminosity gamma-ray bursts turn out to match the best-fit evolution parameter. In the two-population model, the active galactic nuclei is consistent with the best-fit redshift evolution parameter of the pure proton-emitting sources, while the tidal disruption events could be responsible for emitting heavier nuclei. We also compute expected cosmogenic neutrino flux in such a hybrid source population scenario and discuss possibilities to detect these neutrinos by upcoming detectors to shed light on the sources of UHECRs.
© The Author(s) 2021
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Funded by SCOAP3
