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
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
10EV 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.
Keywords
ultra high energy cosmic rays;cosmic ray experiments;Pierre Auger Observatory;active galactic nuclei;
Data
| Language: | English |
|---|---|
| Year of publishing: | 2024 |
| Typology: | 1.01 - Original Scientific Article |
| Organization: | UNG - University of Nova Gorica |
| UDC: | 52 |
| COBISS: |
181667587
|
| ISSN: | 1475-7516 |
| Views: | 330 |
| Downloads: | 7 |
| Average score: | 0 (0 votes) |
| Metadata: |
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Other data
| Pages: | str. 1-40 |
|---|---|
| Volume: | ǂVol. ǂ2024 |
| Issue: | ǂno. ǂ1, [article no.] 022 |
| Chronology: | Jan. 2024 |
| DOI: | 10.1088/1475-7516/2024/01/022 |
| ID: | 22454771 |
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