Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Estimatingthe Contribution of Galactic Neutrino Sources

Mohadeseh Ozlati Moghadam, Kathrin Egberts, Rowan Batzofin, Constantin Steppa, Elisa Bernardini

TL;DR

This work addresses the Galactic neutrino flux by bracketing the source component with two extreme gamma-ray source populations (Model I: maximum; Model II: minimum) and linking gamma rays to neutrinos via a calibrated conversion, normalized to the H.E.S.S. catalog. The authors compare the resulting neutrino flux envelopes to the propagation component from CR interactions with the ISM and to IceCube/ANTARES observations, finding that the combined flux is tightly constrained and leaves little room for large additional source- or CR-driven enhancements. The key finding is that the source component, within the bracketing framework, is within an order of magnitude of the propagation component and often insufficient alone to explain the data, reinforcing the role of propagation while providing meaningful limits on source contributions. These results underscore the constraining power of current neutrino data and highlight the need for next-generation detectors (e.g., KM3NeT, IceCube-Gen2) to sharpen constraints on Galactic neutrino production mechanisms.

Abstract

The Milky Way hosts astrophysical accelerators capable of producing high-energy cosmic rays. These cosmic rays can interact with the interstellar medium (ISM) across the Galaxy to produce neutrinos and gamma rays (propagation component), while their interactions with ambient material at their acceleration sites, such as supernova remnants, can give rise to the source component of the gamma-ray and neutrino flux. In this paper, we estimate the source component of the Galactic neutrino flux using simulated populations of Galactic gamma-ray sources. We compare our results with observations from neutrino experiments in the energy range of 1-30 TeV. Using simulated populations of Galactic TeV gamma-ray sources, we exploit the correlation between gamma rays and neutrinos and introduce a bracketing approach to constrain the range for the source contribution of the Galactic neutrino flux. For the upper limit, we used a simulation describing the entity of Galactic gamma-ray sources, whereas the lower limit was estimated using the hadronic component of the Galactic supernova remnant population. Our results show that the difference between this maximum and minimum is less than an order of magnitude and the flux range is comparable to the Galactic neutrino flux from the cosmic-ray interaction with the ISM. The results agree with the observed signals from IceCube and ANTARES and suggest that the propagation component, combined with the minimum source contribution predicted by the supernova-remnant model, approaches the observed neutrino flux, leaving little room for significant enhancements of the emission originating from propagating cosmic rays.

Estimatingthe Contribution of Galactic Neutrino Sources

TL;DR

This work addresses the Galactic neutrino flux by bracketing the source component with two extreme gamma-ray source populations (Model I: maximum; Model II: minimum) and linking gamma rays to neutrinos via a calibrated conversion, normalized to the H.E.S.S. catalog. The authors compare the resulting neutrino flux envelopes to the propagation component from CR interactions with the ISM and to IceCube/ANTARES observations, finding that the combined flux is tightly constrained and leaves little room for large additional source- or CR-driven enhancements. The key finding is that the source component, within the bracketing framework, is within an order of magnitude of the propagation component and often insufficient alone to explain the data, reinforcing the role of propagation while providing meaningful limits on source contributions. These results underscore the constraining power of current neutrino data and highlight the need for next-generation detectors (e.g., KM3NeT, IceCube-Gen2) to sharpen constraints on Galactic neutrino production mechanisms.

Abstract

The Milky Way hosts astrophysical accelerators capable of producing high-energy cosmic rays. These cosmic rays can interact with the interstellar medium (ISM) across the Galaxy to produce neutrinos and gamma rays (propagation component), while their interactions with ambient material at their acceleration sites, such as supernova remnants, can give rise to the source component of the gamma-ray and neutrino flux. In this paper, we estimate the source component of the Galactic neutrino flux using simulated populations of Galactic gamma-ray sources. We compare our results with observations from neutrino experiments in the energy range of 1-30 TeV. Using simulated populations of Galactic TeV gamma-ray sources, we exploit the correlation between gamma rays and neutrinos and introduce a bracketing approach to constrain the range for the source contribution of the Galactic neutrino flux. For the upper limit, we used a simulation describing the entity of Galactic gamma-ray sources, whereas the lower limit was estimated using the hadronic component of the Galactic supernova remnant population. Our results show that the difference between this maximum and minimum is less than an order of magnitude and the flux range is comparable to the Galactic neutrino flux from the cosmic-ray interaction with the ISM. The results agree with the observed signals from IceCube and ANTARES and suggest that the propagation component, combined with the minimum source contribution predicted by the supernova-remnant model, approaches the observed neutrino flux, leaving little room for significant enhancements of the emission originating from propagating cosmic rays.
Paper Structure (4 sections, 6 equations, 4 figures)

This paper contains 4 sections, 6 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Results
  4. Summary and Conclusion

Figures (4)

  • Figure 1: Spatial distribution of gamma-ray sources from a selected population of model $\mathrm{I}$Steppa_2020 (red circles) and model $\mathrm{II}$batzofin2024SN (blue triangles). The sources follow a four-arm spiral spatial model in the Galactic plane.
  • Figure 2: Comparison of neutrino flux estimates for a single H.E.S.S. source. The solid orange line represents the neutrino flux calculated using the method described in this work; the purple dashed line shows the neutrino flux obtained from the common proportional gamma–neutrino flux relationship (Equation \ref{['eq2']}); and the green dotted line indicates the flux based on the Kelner model from Rowan. The fitted gamma-ray flux is included for reference (gray solid line at the top).
  • Figure 3: The source contribution to the Galactic neutrino flux per flavour, compared with IceCube data. Results are based on all-sky (4$\pi$) templates and are presented as an all-sky flux. The red-shaded band encloses the three IceCube best‑fit normalisations obtained for different Galactic templates IceCubeneutrino. The blue-hatched band shows the flux from Galactic sources bracketed by model $\mathrm{I}$ (upper side: full VHE gamma‑ray population, assumed fully hadronic) and model $\mathrm{II}$ (lower side: hadronic component of the SNR population only). The dotted line represents the propagation component calculated for a homogeneous CR flux according to equation \ref{['diffuse_flux']}.
  • Figure 4: The source contribution to the neutrino flux per flavour in the Galactic Ridge region ($-30^{\circ} < l < 30^{\circ}$, $-2^{\circ} < b < 2^{\circ}$), compared with ANTARES data Galactic_ridge. The blue-hatched band shows the flux from Galactic sources in that area, bracketed by model $\mathrm{I}$ (upper side: full VHE gamma‑ray population, assumed fully hadronic) and model $\mathrm{II}$ (lower side: hadronic component of the SNR population only). The dotted curve shows the emission stemming from propagating CRs calculated for a homogeneous CR sea according to equation \ref{['diffuse_flux']}. The red-shaded band denotes the ANTARES measurement with its $1\sigma$ uncertainty.