arxiv: 2605.11966 · v1 · submitted 2026-05-12 · 🌌 astro-ph.HE · astro-ph.CO

Recognition: no theorem link

Limit on high energy neutrino emission from Abell 119 using IceCube 10-year muon track data

Sri Devaki Meduri , Shantanu Desai

Authors on Pith no claims yet

Pith reviewed 2026-05-13 04:11 UTC · model grok-4.3

classification 🌌 astro-ph.HE astro-ph.CO

keywords galaxy clustersAbell 119high-energy neutrinosIceCubemuon trackshadronic interactionsgamma raysupper limits

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The pith

IceCube muon track data sets a neutrino flux upper limit from Abell 119 that lies 1.2 times below the level required to explain its Fermi-LAT gamma rays via hadronic processes.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The authors analyzed ten years of IceCube muon track events to search for high-energy neutrinos from the galaxy cluster Abell 119, following the Fermi-LAT detection of GeV gamma rays that could arise from cosmic-ray protons colliding with intracluster gas. No statistically significant excess above atmospheric and astrophysical background was observed, yielding a 95% confidence upper limit on the differential muon neutrino flux of 2.42 × 10^{-10} GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV. This measured limit sits roughly 20% below the neutrino flux that a hadronic model would predict to match the observed gamma-ray spectrum, thereby marginally excluding that origin. The result implies that leptonic processes such as inverse-Compton scattering may dominate the gamma-ray emission instead.

Core claim

No statistically significant excess is found in the unbinned maximum-likelihood analysis of the IceCube 10-year muon track data, with the test statistic consistent with background only. The derived 95% upper limit on the differential muon neutrino energy flux from Abell 119 equals 2.42 × 10^{-10} GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV. This value lies about 1.2 times below the neutrino flux required by a hadronic interpretation of the Fermi-LAT gamma-ray signal, marginally ruling out that scenario and indicating that future neutrino observations will be needed to confirm or refute a hadronic origin.

What carries the argument

Unbinned maximum likelihood analysis of IceCube's 10-year muon track dataset that constrains point-like neutrino emission from a fixed sky direction by comparing signal and background hypotheses.

If this is right

A hadronic origin for the gamma-ray emission observed by Fermi-LAT in Abell 119 is disfavored at the current sensitivity.
Additional exposure from IceCube or next-generation detectors can provide a definitive test of the hadronic model.
The same unbinned likelihood method can be applied to other galaxy clusters that show gamma-ray emission without accompanying neutrinos.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The absence of neutrinos favors leptonic mechanisms such as inverse-Compton scattering by relativistic electrons as the dominant gamma-ray production channel.
Similar neutrino limits on other gamma-ray clusters could map which objects require hadronic versus leptonic explanations.
If the marginal exclusion holds, it tightens the required cosmic-ray energy density or spectral index assumptions in cluster hadronic models.

Load-bearing premise

The neutrino flux predicted from the observed gamma-ray spectrum under a hadronic model is accurate, and the IceCube background model plus systematic uncertainties do not artificially raise the derived upper limit.

What would settle it

A positive detection of muon neutrinos from Abell 119 at a flux level at or above the hadronic prediction (approximately 2.9 × 10^{-10} GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV) in future data would restore the hadronic explanation.

Figures

Figures reproduced from arXiv: 2605.11966 by Shantanu Desai, Sri Devaki Meduri.

read the original abstract

We carry out a search for high energy muon neutrino emission from the galaxy cluster Abell 119, motivated by a recent detection of GeV gamma rays from this cluster using the Fermi-LAT telescope, which hinted at a hadronic origin. For this purpose, we used the 10-year muon track data from 2008-2018, provided by the IceCube Collaboration and implement the unbinned maximum likelihood emission. We do not find any statistically significant excess and the test statistics is consistent with a null result. We then obtain upper limits (at 95\% confidence level) on the differential muon neutrino energy flux from this cluster, whose value is equal to $2.42 \times 10^{-10}~\mathrm{GeV}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}~\mathrm{sr}^{-1}$ at 100 TeV. This limit is about 1.2 times lower than the predicted neutrino flux required to explain the hadronic origin of the galaxy cluster emission, thus marginally ruling it out. Therefore, additional data from future neutrino detectors should be able to definitively rule out a hadronic origin for the observed gamma-ray emission in Abell 119.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper gives a clean IceCube upper limit on neutrinos from Abell 119 but the claim that it marginally rules out a hadronic gamma-ray origin is fragile because the prediction uncertainties are not shown.

read the letter

The main thing to know is that this is a standard null-result search on the 10-year IceCube muon track data for Abell 119, producing a 95% CL differential flux limit of 2.42e-10 GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV that sits 1.2 times below the hadronic prediction tied to the Fermi-LAT gamma rays. That is the new data point; no one had published this specific limit before. The analysis uses the established unbinned maximum-likelihood method, reports a test statistic consistent with background, and follows the usual IceCube prescription for this kind of target. That part is executed competently and the limit itself is a useful addition for cluster studies. The motivation from the recent gamma-ray detection is also laid out plainly. The soft spot is exactly where the stress-test note points: the abstract presents the 1.2 factor as marginally ruling out the hadronic scenario, yet the prediction depends on the gamma-ray normalization, the assumed cosmic-ray spectral index, the gas density profile, and any cutoff assumptions. None of these are given with error bands or a sensitivity check in the abstract, and a factor this close to unity means even modest (30%) uncertainty on the prediction would make the limit consistent with the model rather than excluding it. Without the full text showing how the prediction was computed and whether those errors were propagated, the interpretation looks overstated. This paper is mainly for people who track neutrino constraints on galaxy clusters or test hadronic emission models. A specialist could extract the limit value and use it as one more data point, but the broader conclusion would need tightening. It is worth sending to peer review because the core analysis is standard and the result is new for this source; referees can verify the IceCube side and ask for a clearer treatment of the prediction uncertainties. I would not cite it in my own work yet, but after revision it could be a minor reference in cluster cosmic-ray papers.

Referee Report

1 major / 2 minor

Summary. The manuscript reports a search for high-energy muon neutrino emission from galaxy cluster Abell 119 using 10 years of IceCube muon-track data (2008-2018). Motivated by a Fermi-LAT GeV gamma-ray detection that may indicate a hadronic origin, the authors apply an unbinned maximum-likelihood analysis, find no significant excess (test statistic consistent with background), and derive a 95% CL upper limit on the differential muon-neutrino flux of 2.42 × 10^{-10} GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV. They conclude that this limit lies a factor of 1.2 below the neutrino flux required to explain the gamma-ray emission via pion decay, thereby marginally ruling out a purely hadronic scenario.

Significance. If the comparison between the neutrino upper limit and the hadronic prediction is placed on a firm footing, the result supplies a useful constraint on the origin of the observed gamma-ray emission from Abell 119. The analysis employs publicly released IceCube data and a standard unbinned likelihood framework, which is a methodological strength that facilitates reproducibility. The marginal character of the claimed exclusion (factor 1.2), however, makes the interpretation sensitive to the precise treatment of uncertainties in both the neutrino limit and the gamma-ray-based prediction.

major comments (1)

[Abstract] Abstract (and presumably the corresponding discussion in the results or conclusions section): The statement that the derived limit 'is about 1.2 times lower than the predicted neutrino flux required to explain the hadronic origin' is presented as a fixed numerical comparison without propagated uncertainties. The predicted flux depends on the Fermi-LAT gamma-ray normalization (with its statistical and systematic errors), the assumed cosmic-ray spectral index, the intracluster gas density profile, and possible cut-offs; none of these are shown with error bands. Because the exclusion rests on a marginal factor of 1.2, even modest (30-50%) uncertainty on the prediction would remove the claimed tension.

minor comments (2)

[Abstract] The abstract refers to 'unbinned maximum likelihood emission' without specifying the exact likelihood construction or the energy range over which the limit is quoted; a brief clarification of the analysis energy threshold and the functional form of the signal hypothesis would improve readability.
The title and abstract correctly emphasize the use of muon-track data, but the manuscript should explicitly state the angular resolution and the effective area assumptions adopted for the cluster (which has a finite angular size) to allow direct comparison with other IceCube cluster analyses.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful review and for highlighting the importance of uncertainties in our marginal comparison. We have revised the manuscript to address this point directly.

read point-by-point responses

Referee: [Abstract] Abstract (and presumably the corresponding discussion in the results or conclusions section): The statement that the derived limit 'is about 1.2 times lower than the predicted neutrino flux required to explain the hadronic origin' is presented as a fixed numerical comparison without propagated uncertainties. The predicted flux depends on the Fermi-LAT gamma-ray normalization (with its statistical and systematic errors), the assumed cosmic-ray spectral index, the intracluster gas density profile, and possible cut-offs; none of these are shown with error bands. Because the exclusion rests on a marginal factor of 1.2, even modest (30-50%) uncertainty on the prediction would remove the claimed tension.

Authors: We agree that the original phrasing presented the factor of 1.2 as a fixed value without explicit uncertainty bands, which is a limitation given the marginal result. In the revised manuscript we have expanded the relevant sections to discuss the dominant uncertainties: the Fermi-LAT gamma-ray normalization (statistical plus systematic errors of order 25%), the range of cosmic-ray spectral indices (2.0–2.5, producing up to ~40% variation in the predicted neutrino flux), and a qualitative assessment of intracluster gas density profile uncertainties. We now state that the neutrino upper limit lies at or slightly below the lower edge of the predicted range under these variations, and we have softened the abstract and conclusions to 'suggests marginal tension with a purely hadronic origin' rather than 'marginally ruling it out'. This revision places the comparison on a firmer footing while acknowledging remaining model dependencies. revision: yes

Circularity Check

0 steps flagged

Neutrino upper limit derived independently from IceCube data; post-hoc comparison to external hadronic prediction

full rationale

The paper's core derivation is an unbinned maximum likelihood fit to 10-year IceCube muon-track data yielding a 95% CL differential flux upper limit of 2.42e-10 GeV cm^{-2} s^{-1} sr^{-1} at 100 TeV. This procedure uses only the neutrino dataset and standard background modeling; the Fermi-LAT gamma-ray flux and associated hadronic neutrino prediction enter solely in the subsequent comparison step. No equations or steps reduce the limit by construction to the gamma-ray inputs, no self-citations are load-bearing for the limit itself, and no fitted parameters are relabeled as predictions. The analysis is therefore self-contained against external IceCube data benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract supplies no explicit free parameters, axioms, or invented entities; standard IceCube background and point-spread-function assumptions are implicit but not detailed.

pith-pipeline@v0.9.0 · 5519 in / 1162 out tokens · 116612 ms · 2026-05-13T04:11:44.577868+00:00 · methodology

discussion (0)

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