PREreview of Modeling individual nearby radio galaxies as ultra-high-energy cosmic-ray accelerators

summary: 'Modeling individual nearby radio galaxies as ultra-high-energy cosmic-ray accelerators by Andressa Colaço Gabriel Azeredo Isadora Parillo Caina de Oliveira and Vitor de Souza develops a source-resolved physically motivated framework to quantify the contributions of Centaurus A Virgo A and Fornax A to the UHECR flux observed by the Pierre Auger Observatory. The study combines jet-acceleration–derived injection spectra (PLEC/DPLEC) a composition motivated by Wolf–Rayet winds and CRPropa-based extragalactic propagation (no magnetic fields) with a likelihood fit to the Auger energy spectrum. The authors find that a small set of nearby FR-I radio galaxies with acceleration efficiencies of order 10^-3–10^-2 can reproduce the highest-energy spectrum yield broadly consistent high-energy composition trends and predict low secondary-neutrino fluxes from local sources—while a distant radio-galaxy background remains subdominant.'

keywords:'ultra-high-energy cosmic rays, UHECR, radio galaxies, FR-I, Centaurus A, Virgo A, Fornax A, AGN jets, particle acceleration, diffusive shock acceleration, shear acceleration, espresso acceleration, PLEC, DPLEC, break energy, jet power, Ebreak, Pierre Auger Observatory, CRPropa, extragalactic propagation, EBL Gilmore12, mass composition, Xmax, neutrinos, anisotropy, background source population, likelihood fit'

score: 78

tier: 'Tier3 (Top-field journals): Strong physical motivation and source-resolved modeling with good spectrum fits and sensible efficiency estimates; however robustness is limited by neglect of magnetic fields and modest treatment of systematics. With revisions addressing these it is competitive for top-field venues.'

CPI: 0.67

expected_citations_2yr: 13

categories:

Abstract:

score: 9

description: 'Clear and self-contained: states objectives (source-resolved modeling of three nearby FR-I galaxies) methods (physically motivated spectra + CRPropa propagation + spectrum-only fit) and conclusions (few nearby sources can explain highest-energy UHECRs with η~10^-3–10^-2; low local neutrino flux).'

Recency:

score: 9

description: 'Citations include 2023–2025 results (e.g. recent Auger composition CRPropa 3.2 updated RLFs) aligning well with a 2026 preprint.'

Scope:

score: 9

description: 'The manuscript’s content matches the title and implied scope: individual modeling of nearby radio galaxies as UHECR accelerators plus a statistical background.'

Relevance:

score: 9

description: 'Highly relevant to UHECR origin studies and JCAP’s audience; advances beyond homogeneous-population treatments by source-resolving nearby FR I galaxies.'

'Factual Errors':

score: 9

description: 'No clear factual errors detected; assumptions (e.g. neglect of magnetic fields composition choices) are stated as modeling choices and discussed as limitations.'

Language:

score: 8

description: 'Scientific tone and clarity are strong; minor typographic artifacts from typesetting (hyphenation/line breaks) do not impede understanding.'

Formatting:

score: 8

description: 'Structure follows standard scientific layout with clear sections equations and appendices; minor line-break artifacts in headings but overall consistent.'

Suggestions:

score: 8

description: 'New elements include source-resolved FR-I modeling with DPLEC spectra tied to jet parameters and an RLF-based background. To strengthen novelty and impact: (1) include GMF/EGMF lensing to jointly fit spectrum+anisotropy; (2) perform hierarchical Bayesian inference with parameter correlations; (3) jointly fit Xmax alongside the spectrum; (4) release code and weights; (5) test EBL/hadronic-model systematics explicitly; (6) cross-check with gamma-ray constraints on hadronic cascades.'

Problems:

score: 8

description: 'Addresses the gap between population-averaged models and source-specific modeling and replaces ad hoc injection laws with physically motivated spectra. It also examines practical significance via η constraints and composition trends.'

Assumptions:

score: 6

description: 'Key assumptions (no magnetic fields in propagation; Wolf–Rayet-dominated heavy composition; Ebreak–Qjet scaling; fixed f in radio–jet-power conversion; spectrum-only fit) are reasonable but limit external validity; some are only partially justified.'

Consistency:

score: 7

description: 'Best-fit scenarios reproduce the high-energy spectrum and broadly align with composition trends at the highest energies; some scenarios conflict with lower-energy composition which the authors acknowledge.'

Robustness:

score: 7

description: 'Scenario variations (PLEC vs DPLEC; inclusion of background) and parameter scans are explored; however neglect of GMF/EGMF and limited systematics exploration temper robustness.'

Logic:

score: 8

description: 'Conclusions follow from the model fits and propagation results; caveats about Fornax A past activity and Virgo A suppression are plausibly argued.'

'Statistical Analysis':

score: 7

description: 'Likelihood-based fits with Gaussian/Poisson treatment and deviance per dof are appropriate; uncertainties in η are reported. Missing are parameter correlation matrices energy-scale/systematic nuisance treatment and cross-validation with composition in the likelihood.'

Controls:

score: 'N/A'

description: 'Controls pertain to laboratory/observational experiments without modeling/simulation components; this work is primarily simulation and modeling with observational comparison.'

Corrections:

score: 6

description: 'Propagation accounts for key energy-loss processes and EBL; however no correction or marginalization for Auger energy-scale systematics hadronic-model systematics in composition or EGMF/GMF effects in flux normalization.'

Range:

score: 9

description: 'Fit ranges (5–200 EeV and 20–200 EeV) cover the regimes of interest and align with prior literature and detector sensitivity.'

Collinearity:

score: 5

description: 'Potential degeneracy among source and background contributions (similar propagated spectral shapes) is likely; the analysis does not report covariance/correlation matrices or identifiability diagnostics.'

'Dimensional Analysis':

score: 9

description: 'Equations are dimensionally consistent (e.g. Ebreak–Qjet scaling uses a dimensionless exponent; spectra and normalizations are coherent).'

'Experimental Design':

score: 7

description: 'Simulation design is documented (CRPropa settings EBL model shell sampling weighting). Improvements: include 3D propagation with GMF/EGMF quantify sensitivity to EBL/hadronic models and RLF evolution and provide code/data for replication.'

'Ethical Standards':

score: 'informational'

description: 'No human/animal subjects or dual-use concerns. Acknowledge HPC resources and funding. Recommend adding a brief ethics/compliance statement and data/code availability to improve transparency and replicability.'

'Conflict Of Interest':

score: 'informational'

description: 'No conflicts stated; funding acknowledged. Include an explicit COI statement declaring none or disclosing any relevant ties.'

Normalization:

score: 'informational'

description: 'Experimental data normalization is not directly applicable; for simulations the manuscript details flux normalization via weighting (Appendix A). For observational comparisons consider explicitly stating any exposure/acceptance normalizations used.'

'Idea Incubator':

score: 'informational'

description: 'Cross-disciplinary analogies: (1) Portfolio theory (economics): UHECR flux as a portfolio where nearby sources carry higher weight due to lower risk (losses/deflections); diversification maps to background contribution. (2) Metapopulation dynamics (ecology): Source colonies (galaxies) seed patches (energy bins) via dispersal (propagation); colonization-extinction balance maps to spectral suppression and composition shift. (3) Resonance/quality factor (physics): High-Q resonances correspond to sources with spectra tightly peaked near Ebreak; damping represents energy losses and magnetic scattering. (4) Observer design (control theory): Estimating hidden states (η composition) from outputs (spectrum) with an observer; robustness improves by adding sensors (anisotropy Xmax neutrinos). (5) Channel capacity (information theory): Propagation as a noisy channel with constraints (energy losses disintegration); coding strategy maps to composition and injection spectra optimizing mutual information with observations. (6) Traffic flow/queuing networks: Particles as customers interactions as service nodes; bottlenecks (GZK interactions) set throughput and composition-dependent delays.'

'Improve Citability':

score: 'informational'

description: 'To maximize reusability and citations: (1) Release CRPropa configs weighting scripts and minimization code with a DOI; (2) Provide machine-readable tables for best-fit spectra η posteriors and predicted ⟨lnA⟩; (3) Supply GMF/EGMF-ready source files to enable anisotropy studies; (4) Include a systematic-uncertainty budget and sensitivity tables (EBL hadronic models RLF evolution f-factor); (5) Offer a simple surrogate model (e.g. spline/parametric fit) for quick reuse; (6) Add a reproducibility checklist with random seeds and software versions.'

Falsifiability:

score: 'informational'

description: 'Primary claims: (a) A few nearby FR-I radio galaxies can dominate the highest-energy UHECR flux with η~10^-3–10^-2; (b) resulting composition trends at the highest energies are broadly consistent; (c) local-source neutrino flux is well below near-term sensitivities. Potential falsifiers: (1) Future Auger/TA measurements showing significantly lighter composition above ~40 EeV than predicted; (2) robust detection of a strong UHE neutrino flux attributable to local AGN inconsistent with heavy-dominated injection; (3) anisotropy patterns incompatible with dominant contributions from Cen A/For A after accounting for GMF; (4) improved jet measurements ruling out the required Ebreak–Qjet relation or η values; (5) joint spectrum+Xmax fits decisively disfavoring WR-like compositions for these sources.'

Competing interests

The author declares that they have no competing interests.

Use of Artificial Intelligence (AI)

The author declares that they used generative AI to come up with new ideas for their review.