{"id":"1f279868-8d4e-4f94-8a3d-6fdb47a86689","arxiv_id":"1908.06658","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"Three HAWC gamma-ray sources previously undetected by H.E.S.S. show significant H.E.S.S. emission when the map is smoothed to HAWC resolution and an acceptance-map background is used.","lead":"This paper compares HAWC and H.E.S.S. views of the Galactic plane in TeV gamma rays, and shows that when H.E.S.S. maps are processed similarly to HAWC maps, three previously undetected HAWC sources show significant emission in H.E.S.S. data. The result highlights that background estimation is the dominant cause of apparent disagreement between the two instruments.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The claimed >5σ detections hinge on an acceptance-map background whose normalization is not validated; the paper's own caveat about systematic residuals for extended sources is left unquantified.","rationale":"The reader's weakest_assumption is exactly the acceptance-map background systematics, and the paper itself flags this as future work. The reader's verdict of CONDITIONAL is appropriate: the claim is plausible but rests on an unvalidated background method. The strongest claim in Section 4 is directly undermined if the acceptance-map background has unquantified large-scale residuals or normalization errors. The paper provides no demonstration that the acceptance-map background is unbiased in the H.E.S.S. data, no estimate of systematic error, and no alternative background comparison. The three candidate sources are extended and located in complex regions of the Galactic plane, making the risk of background mis-modeling substantial. However, the paper is a preliminary conference proceedings, and the method is a natural approach that could be validated; therefore, the verdict should remain CONDITIONAL rather than REJECT. The reader's weakest_assumption identifies the same concern, so agreement is 'agree'.","tokens_in":4527,"tokens_out":1507,"duration_ms":14138,"concrete_test":"Recompute the significance of HAWC J1928+178, J1914+118, and J1909+083 using an alternative background estimate: e.g., the H.E.S.S. ring background with fixed (non-adaptive) parameters and no exclusion band, or a two-dimensional acceptance map fit to event counts while masking all known sources. If the three excesses drop below 5σ or shift significantly in position under this alternative, the >5σ claim is not robust. Also provide the systematic uncertainty on the acceptance-map normalization derived from the scatter of background counts in source-free regions.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim in Section 4 is that 3 HAWC sources previously undetected by H.E.S.S. appear at >5σ when the H.E.S.S. map is smoothed to HAWC resolution and the field-of-view (acceptance-map) background is used. This method is developed for wide-field instruments: the acceptance map is built by integrating all events in 2-hour periods. For a pointing IACT such as H.E.S.S., the acceptance is strongly position-dependent and varies run-by-run due to pointing direction, zenith angle, and atmospheric conditions. The paper does not show how the acceptance map is constructed for H.E.S.S. data, how many runs are combined, how the acceptance is normalized, or how large-scale residuals are suppressed. A critical risk is that the acceptance map over-subtracts or under-subtracts at the positions of the three candidate sources, producing apparent excesses of a few σ that are then amplified to >5σ by the 0.4° smoothing. The authors themselves state in Section 4 that 'a closer look needs to be taken at the systematics of this approach for very extended sources.' The source size is the key unknown: if the three HAWC sources have substantial angular extent, the acceptance-map background may be biased by gamma-ray emission leaking into the acceptance estimate, or the ring background may partially remove real extended emission. The paper provides no estimate of the systematic uncertainty on the background normalization, nor a comparison of the acceptance-map background with the standard ring background in regions with no known sources, which would reveal large-scale residuals. Consequently, the >5σ significance and the conclusion that 'both instruments agree and observe the same TeV sky' are not yet robust.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This ICRC 2019 proceedings contribution compares the H.E.S.S. Galactic Plane Survey with the HAWC 2HWC catalog in the overlapping longitude range, aiming to understand why some HAWC sources lack H.E.S.S. counterparts. The authors smooth the H.E.S.S. map with a 0.4° top-hat to match HAWC's PSF and replace the standard ring background with a field-of-view (acceptance-map) background. With this modified map-making, three HAWC sources previously undetected by H.E.S.S. (HAWC J1928+178, HAWC J1914+118, HAWC J1909+083*) are claimed to show >5σ significance in the H.E.S.S. data. The authors conclude that the two instruments observe the same TeV sky and that background estimation explains most apparent catalog differences.","tokens_in":4872,"tokens_out":6722,"duration_ms":65451,"significance":"If correct, the result is significant: it would demonstrate that part of the apparent discrepancy between the H.E.S.S. and HAWC catalogs is a consequence of different background-estimation methods, and that the field-of-view background method can be useful for detecting extended emission in IACT data. The paper's parameters (smoothing radius 0.4°, latitude exclusion band ±1°) are fixed by instrument characteristics rather than tuned to produce detections, which is a point in its favor. However, the analysis is explicitly preliminary: there is no description of the construction and normalization of the acceptance map for H.E.S.S., no systematic uncertainty on the claimed >5σ detections, and the paper itself calls for further study of the systematics for extended sources. The central claim is therefore not yet established to the standard expected for a refereed journal.","major_comments":[{"comment":"The field-of-view (acceptance-map) background method, applied here to H.E.S.S. for the first time, is described only by reference to the HAWC direct-integration method [2]. The manuscript does not state how many H.E.S.S. runs are combined, what time period is used for acceptance estimation, how the acceptance is normalized to the counts in each pixel, or how the strong run-to-run variations in pointing direction, zenith angle, and atmospheric transmission of an IACT are handled. Because the claimed >5σ excesses in Section 3 are computed relative to this background, the entire central claim depends on an unvalidated procedure. The authors need to provide a step-by-step description and a validation test, for example, comparing the acceptance-map background with the ring background on sources of known morphology or showing that the residuals in source-free regions are consistent with zero.","section":"Section 2.2"},{"comment":"The paper quotes the three excesses as 'more than 5σ' but gives no systematic uncertainties. The 0.4° top-hat smoothing can amplify broad residual features, and the authors' own statement in Section 4, that 'a closer look needs to be taken at the systematics of this approach for very extended sources', concedes that the method is not yet validated for the source class in question. To support the central claim, the authors must demonstrate that the >5σ significance survives variations of the acceptance-map construction (integration period, exclusion band, normalization region) and of the smoothing radius. Without such a study, the quoted significances are only statistical.","section":"Sections 3 and 4"},{"comment":"The statement that 'the non detection of the 6 other HAWC sources is consistent in terms of sensitivity as long as sources are more extended than 0.1°' is not supported by any calculation shown in the paper. The authors should present the expected H.E.S.S. significance as a function of source extension and flux for the two background methods, or remove the statement.","section":"Section 3"},{"comment":"The conclusion that 'both instruments agree very well with each other and that they observe the same TeV sky' goes beyond the evidence presented. The analysis recovers 3 of 9 previously undetected HAWC sources and leaves 6 sources without significant H.E.S.S. emission. The conclusions should be limited to what the data show, or a quantitative detection-completeness model should be provided.","section":"Section 4 and Abstract"}],"minor_comments":[{"comment":"The longitude range '60° < ℓ < 10°' is mathematically inconsistent; the intended range is presumably 10° < ℓ < 60°.","section":"Section 2"},{"comment":"In the third paragraph, 'the H.E.S.S. map is convoled with a top hat function' should read 'convolved'.","section":"Section 2.1"},{"comment":"In the sentence 'This technique seems promising to detect extended sources, eventhough a closer look needs to be taken', 'eventhough' should be 'even though'.","section":"Section 4"},{"comment":"The caption refers to 'second row' and 'bottom row' but the figure appears to contain more than two rows; please identify each row explicitly so the reader can map the panels to the background methods.","section":"Figure 3 caption"}],"recommendation":"major_revision","confidential_remarks":"This is a conference proceedings and the figures are labeled 'PRELIMINARY', but the central claim is published without the technical detail needed to assess it. I recommend major revision rather than rejection because the required additions—detailed acceptance-map description, systematic checks, and a sensitivity calculation—are feasible within the scope of a regular paper. If the venue cannot accommodate such additions, the editors may wish to consider whether the 'preliminary' caveat is sufficient for the claims made."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First thing to know: this is a six-page ICRC proceedings paper, not a full journal article. It reports a preliminary cross-calibration of the H.E.S.S. Galactic plane survey with HAWC. The concrete new result is that three HAWC sources — J1928+178, J1914+118, J1909+083 — that had no H.E.S.S. counterpart show up at >5σ in the H.E.S.S. map once the map is smoothed with a 0.4° top hat and the background is estimated with the acceptance-map (field-of-view) method rather than the usual ring background. That is a real, falsifiable claim and I don't think it appears elsewhere.\n\nWhat the paper does well: it is transparent about the method and about its own limits. The parameters — smoothing radius, exclusion band — are set by instrument properties, not tuned to make these sources appear. The authors explicitly state that a closer look at systematics is needed for very extended sources and that spectral/morphological analysis is future work. For a conference contribution, that is the right tone.\n\nWhere I'd push: the stress-test note is on target. The acceptance-map background is standard for wide-field instruments like HAWC, but for a pointing IACT the acceptance varies run-by-run with zenith, atmospheric conditions, and pointing offset. The paper does not show how the acceptance map is built from H.E.S.S. data, how runs are combined, or how large-scale residuals are suppressed. Without that, a 5σ excess could be a systematic gradient that the smoothing amplifies. The paper also doesn't compare the acceptance-map background to the ring background in source-free regions, which would be the natural control. And because the three sources are extended at HAWC energies, the ring background's tendency to remove large-scale emission is exactly the failure mode being tested — so the claim that the sources were 'previously undetected' is partly a statement about background subtraction, not about the sky.\n\nThat said, the central idea is credible. The paper does not over-claim; it presents a promising first look. For a journal submission it would need an actual background-validation section, with estimates of systematic uncertainties and maybe a run-by-run acceptance consistency check. For an ICRC proceedings, it is adequate as a preliminary.\n\nWho it's for: gamma-ray astronomers working on TeV surveys, especially anyone combining IACT and wide-field data. I'd bring it to a reading group and would cite it as evidence that cross-instrument background choices matter. I'd send it to peer review if it were submitted as a research note, with the expectation that the referee asks for the missing validation; I would not accept the >5σ wording as-is.","headline":"Short ICRC paper showing three HAWC sources absent from H.E.S.S. catalogues appear at >5σ after smoothing to HAWC resolution and switching from ring to acceptance-map background; plausible but the background systematics are not yet quantified.","tokens_in":5410,"tokens_out":3354,"would_cite":true,"duration_ms":34585,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Three HAWC sources reappear in H.E.S.S. data when backgrounds are matched","keywords":["TeV gamma-ray astronomy","Galactic plane survey","HAWC","H.E.S.S.","background estimation","extended sources","source catalog comparison","acceptance map method"],"falsifier":"Take a H.E.S.S. field with no known gamma-ray sources, build the same acceptance-map background, and count how often >5σ extended features appear; if spurious features appear at a comparable rate to the three recovered sources, the detections are background artifacts. Alternatively, inject simulated extended sources into H.E.S.S. event data and verify that the acceptance-map method recovers them at the claimed significance while the ring method does not.","tokens_in":4292,"feed_emoji":"🌌","tokens_out":8093,"duration_ms":73298,"temperature":0.7,"pith_summary":"The paper sets out to resolve an apparent mismatch between two maps of the Milky Way in very-high-energy gamma rays. HAWC, a wide-field observatory, reports nine Galactic-plane sources that the H.E.S.S. catalog, built from pointed observations, does not contain. The authors reprocess H.E.S.S. survey data with a background estimator closer to HAWC's acceptance-map method and smooth the H.E.S.S. map to HAWC's angular resolution; three of the nine sources then appear in H.E.S.S. data at more than 5σ significance, within half a degree of the HAWC positions. Their conclusion is that both instruments observe the same TeV sky and that most apparent catalog differences are actually artifacts of background estimation, not real disagreements about what is out there.","feed_headline":"Three HAWC sources reappear in H.E.S.S. data when backgrounds are matched","feed_subtitle":"Apparent TeV sky mismatches shrink when extended emission and background estimation are treated the same way.","key_machinery":"The mechanism that carries the argument is the field-of-view background method, also called the acceptance-map method, applied for the first time to a H.E.S.S. Galactic-plane map. Unlike the ring background method, which estimates the background for each pixel from an annulus around it and can swallow extended source emission, the acceptance-map method builds the background from all events integrated over time, preserving large-scale structure. The second ingredient is angular-resolution matching: convolving the H.E.S.S. significance map with a 0.4°-radius top hat so that extended emission is integrated the way HAWC's wider point-spread function integrates it. Together, these two changes are what make the three recovered sources cross the 5σ threshold.","core_discovery":"The central discovery is that a change in map-making procedure removes most of the apparent disagreement between the HAWC and H.E.S.S. Galactic-plane source lists. Using H.E.S.S. data above 1 TeV, the authors replace the adaptive ring background with a field-of-view acceptance-map background and convolve the significance map with a top-hat of 0.4° radius, matching HAWC's point-spread function. In this reprocessed map, three HAWC sources previously missing from the H.E.S.S. catalog — HAWC J1928+178, HAWC J1914+118, and HAWC J1909+083* — show emission exceeding 5σ within half a degree of the HAWC locations. The authors conclude that the ring background method tends to absorb large-scale emission around extended sources, and that once this is corrected the two instruments agree on the same TeV sky.","pith_inferences":["I infer that the same acceptance-map reanalysis could be applied to archival data from other pointed Cherenkov telescopes, potentially revealing extended sources that ring-type backgrounds suppressed there as well.","I infer that the six remaining HAWC-only sources are the discriminating test of the paper's background story: if they are genuinely extended, deeper H.E.S.S. observations with the field-of-view background should recover some of them.","The paper leaves systematics for very extended sources open; a direct calibration would inject simulated sources of known size into H.E.S.S. data and measure how much signal each background method removes, quantifying the correction rather than inferring it.","A natural next step, not taken here, is a joint likelihood fit of the unsmoothed HAWC and H.E.S.S. maps with a single morphological model and per-instrument background models, instead of comparing thresholded source lists."],"forward_implications":["If the central claim is right, the HAWC and H.E.S.S. catalogs are two views of the same TeV sky; apparent mismatches mostly trace to analysis choices rather than to source variability or instrument blindness.","Standard ring-background H.E.S.S. maps can hide extended emission, so source catalogs built from them are incomplete for sources larger than the ring's inner radius.","The three recovered associations — HAWC J1928+178, HAWC J1914+118, and HAWC J1909+083* — become concrete targets for deeper H.E.S.S. follow-up to pin down their morphology and spectrum.","The six HAWC sources still absent from the H.E.S.S. map are, by the paper's sensitivity argument, consistent with sources more extended than about 0.1°, a size that future joint fits could constrain.","Combining a wide-field survey like HAWC with pointed follow-up like H.E.S.S. is a more complete way to map the TeV Galactic plane than either instrument alone."],"supporting_citations":[{"why":"Supplies the H.E.S.S. Galactic Plane Survey data set and the standard ring-background map that this paper reprocesses.","marker":"[1]"},{"why":"Defines the HAWC event nHit bins and the direct-integration acceptance-map background used for the HAWC side of the comparison.","marker":"[2]"},{"why":"Provides the 2HWC HAWC source catalog, including the nine sources not matched to H.E.S.S. that drive the analysis.","marker":"[3]"},{"why":"Provides the ImPACT template-based event reconstruction used to reprocess H.E.S.S. data above 1 TeV.","marker":"[4]"},{"why":"Introduces the field-of-view acceptance-map background method that, applied to H.E.S.S. data, is the key procedural change recovering the three sources.","marker":"[5]"}],"fun_headline_variants":["Matched analysis uncovers three HAWC sources in H.E.S.S. data","Background fix aligns HAWC and H.E.S.S. Galactic views","Three TeV sources resurface in H.E.S.S. after reanalysis","Reanalysis erases HAWC-H.E.S.S. source mismatch","Same TeV sky: HAWC and H.E.S.S. see eye to eye"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the acceptance-map background, when applied to H.E.S.S. data, does not create large-scale systematic residuals that mimic extended gamma-ray emission at the >5σ level; the paper itself flags this as needing a closer look for very extended sources.","fun_headline_variants_meta":{"raw":{"variants":["Matched analysis uncovers three HAWC sources in H.E.S.S. data","Background fix aligns HAWC and H.E.S.S. Galactic views","Three TeV sources resurface in H.E.S.S. after reanalysis","Reanalysis erases HAWC-H.E.S.S. source mismatch","Same TeV sky: HAWC and H.E.S.S. see eye to eye"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000243,"raw_usage":{"total_tokens":1523,"prompt_tokens":931,"completion_tokens":592,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":547,"completion_tokens_details":{"reasoning_tokens":492}},"tokens_in":547,"tokens_out":592,"duration_ms":6369,"temperature":1.0,"reasoning_tokens":492,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T12:36:51.808798+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Take a H.E.S.S. field with no known gamma-ray sources, build the same acceptance-map background, and count how often >5σ extended features appear; if spurious features appear at a comparable rate to the three recovered sources, the detections are background artifacts. Alternatively, inject simulated extended sources into H.E.S.S. event data and verify that the acceptance-map method recovers them at the claimed significance while the ring method does not.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the H.E.S.S. Galactic Plane Survey data set and the standard ring-background map that this paper reprocesses."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Defines the HAWC event nHit bins and the direct-integration acceptance-map background used for the HAWC side of the comparison."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the 2HWC HAWC source catalog, including the nine sources not matched to H.E.S.S. that drive the analysis."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the ImPACT template-based event reconstruction used to reprocess H.E.S.S. data above 1 TeV."},{"cited_title":"and Funk, S","cited_arxiv_id":null,"evidence_quote":"Introduces the field-of-view acceptance-map background method that, applied to H.E.S.S. data, is the key procedural change recovering the three sources."}],"review_version":1}