Determine the origin of the 0.1–100 GeV emission from NGC 4151

Determine the physical origin of the 0.1–100 GeV gamma-ray emission observed toward NGC 4151, distinguishing between contamination, an ultra-fast outflow, and emission produced in the black-hole corona.

Background

The paper compares leptonic emission from nonthermal primary electrons with hadronically induced electromagnetic cascades in the corona of NGC 4151. Although the modeled MeV-to-GeV spectrum can be constrained using Fermi-LAT observations, the authors note that the association and physical origin of the observed 0.1–100 GeV emission are unsettled. Possible explanations include contamination from unrelated sources, an ultra-fast outflow, or gamma-ray production in the corona itself. Resolving this ambiguity is important for interpreting the relative leptonic and hadronic contributions and for assessing whether the gamma-ray data can constrain coronal particle acceleration.

References

Note that the origin of the $0.1-100$\,GeV Fermi-LAT emission toward NGC\,4151 remains debated, owing to possible contamination \citep{muraseSubGeVGammaRays2024,Peretti:2023crf}; Fig.~\ref{fig:proton_photon_neutrino_stat} includes both sets of measurements. Even if this emission originates from NGC\,4151, its physical origin remains disputed: it could arise from an ultra-fast outflow \citep{Peretti:2023crf,Neher:2026gct}, or from the corona.

— Gamma-rays from black hole coronae: disentangling the leptonic and hadronic contributions  (2610.09676 - Bihan et al., 7 Oct 2026) in Section 3, “Results for NGC 4151”