{"id":"4a74c352-ec12-4d01-8e6d-3e03e2a99fd1","arxiv_id":"2607.29091","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"A shear×velocity kSZ template cross-correlated with the CMB is forecast to measure the electron–matter power spectrum to few-percent (ACT/SO) or sub-percent (CMB-HD) precision.","lead":"This paper forecasts a new way to measure how gas around dark matter halos scatters CMB photons: a kSZ template built from weak-lensing convergence times reconstructed galaxy velocities is cross-correlated with the CMB temperature. If it works, it can calibrate the leading baryonic-feedback systematic for Rubin and Roman weak-lensing surveys without modeling galaxies.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The few-percent constraints on baryonic suppression assume P_em≈P_bm (§3.1); that electron-baryon mapping is unvalidated and could bias the headline claim at the claimed precision level.","rationale":"The reader's weakest-assumption identification aligns with my own: the P_em≈P_bm mapping in §3.1 is the point where the central claim—measuring baryonic suppression of the matter power spectrum—is least secure. The paper's derivation of the estimator's sensitivity to P_em is coherent and supported by the analytic expressions in App. A, and the forecasts are standard. However, the purpose is not merely to detect P_em but to constrain baryonic feedback in cosmic shear. That step requires identifying free electrons with the total baryon distribution, which is a physical assumption about gas physics on precisely the small scales where feedback operates. The paper offers no simulation-based or empirical validation of this ratio, and its one-line SNR-to-precision conversion assumes the mapping is exact. I do not see an internal inconsistency; the issue is an unquantified systematic that could move the claimed constraints by an amount comparable to the stated error bars. Because the reader already marked the paper CONDITIONAL on this and related assumptions, my assessment does not change the verdict; it reinforces it. I would add the concrete simulation test as a required validation before the headline precision can be trusted.","tokens_in":26892,"tokens_out":6019,"duration_ms":72263,"concrete_test":"Run a hydrodynamical simulation (e.g., FLAMINGO, IllustrisTNG, or BAHAMAS) and compute both P_em(k,z) (from free electrons only) and P_bm(k,z) (from all baryons) at z≈0.5–2 and k=0.1–10 h/Mpc. Evaluate the ratio P_em/P_bm and compare the deviation from unity with the claimed statistical precision (few percent for ACT/SO, sub-percent for CMB-HD). Then insert the simulated P_em into Eq. (3.3) to infer δP/P_mm and compare with the true simulated suppression; if the bias exceeds the statistical error, the headline interpretation needs revision.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim converts a measured electron–matter cross-spectrum P_em into a constraint on the baryonic suppression of the matter power spectrum via Eq. (3.3), which explicitly assumes free electrons trace all baryons (P_em≈P_bm). This assumption is stated but not tested. On the scales where baryonic feedback matters most (k≳1 h/Mpc), the ionized gas distribution can differ from the total baryon distribution: stars and cold neutral gas contribute to P_bm but not to P_em, and the spatial segregation between hot ionized gas and condensed phases can be significant. The claimed statistical precision is 2–5% (ACT/SO) and <1% (CMB-HD) on the suppression amplitude. If P_em/P_bm deviates from unity by even a few percent on these scales, the inferred suppression is biased by an amount comparable to or exceeding the claimed precision. The paper does not quantify this ratio from simulations or analytic models, nor does it propagate the uncertainty into the final constraints. This is the single most load-bearing assumption because, without it, the method measures P_em—a useful observable—but not the baryonic suppression of P_mm that is the headline result. The concern is distinct from the snapshot approximation, which the paper itself flags, and from the well-modeled large-scale velocity reconstruction; it is an unvalidated physical mapping at the heart of the interpretation.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper proposes a new estimator for the baryonic contribution to weak-lensing signals. The kSZ template \\hat{T}_{i,\\alpha} = K_i V_\\alpha is formed by multiplying tomographic weak-lensing convergence maps with reconstructed radial-velocity maps, then cross-correlated with CMB temperature maps. The signal is shown to be proportional to the electron–matter power spectrum P_em, and BNT nulling is used to localize the measurement in redshift. Forecasts are computed for Rubin LSST Y10 and Roman kinematic-lensing samples combined with ACT, SO, and CMB-HD, using a Battaglia AGN-feedback model for P_em and Gaussian covariance. The paper reports SNR ≈ 5–15 for current/upcoming CMB experiments and ≳100 for CMB-HD, and interprets these as few-percent and sub-percent constraints on the baryonic suppression of the matter power spectrum. Detailed derivations are provided in appendices.","tokens_in":27151,"tokens_out":11964,"duration_ms":131957,"significance":"If the central assumption P_em ≈ P_bm can be validated, this is a novel and valuable probe: it avoids modeling the galaxy–matter connection, it is linear in the CMB temperature and therefore less sensitive to foregrounds than ⟨T²g⟩ estimators, and the BNT nulling enables redshift-resolved measurements. The analytic derivation in App. A is coherent and the appendices provide enough detail for the forecast to be reproduced. The authors are also transparent about several limitations, including shape noise, velocity-reconstruction noise, and the modest correlation coefficient for CMB map cleaning. However, the headline precision claim is statistical and conditional on a physical mapping that is not demonstrated. The paper would be substantially strengthened by quantifying P_em/P_bm and the neglected ⟨δ_e v_r⟩ term.","major_comments":[{"comment":"The headline conversion from the measured cross-spectrum to the baryonic suppression of P_mm rests on the one-line assumption that free electrons trace all baryons, P_em ≈ P_bm. This is not tested. On the scales where feedback matters (k ≳ 1 h/Mpc), a non-negligible baryon fraction resides in stars and cold neutral gas, which do not contribute to P_em, and the hot ionized gas is spatially segregated from these condensed phases. If P_em/P_bm deviates from unity by a few percent, the inferred suppression is biased by an amount comparable to the claimed 2–5% (ACT/SO) or <1% (CMB-HD) statistical precision. The paper should quantify this ratio using hydrodynamical simulations (e.g., FLAMINGO, IllustrisTNG, or at least a two-phase model) and propagate it as a systematic, or explicitly reframe the claim as a measurement of P_em rather than of the baryonic suppression of P_mm.","section":"§3.1, Eq. (3.3)"},{"comment":"The Wick contraction yields three terms; the second (and third) is dropped with the argument 'P_evr ∼ 1/k P_em.' This argument is incomplete: the retained term contains P_em P_vrvr, and P_vrvr ∼ P_mm/k², so the ratio of the dropped term to the retained term is of order P_em/P_mm, not 1/k. Unless the k_∥/K_∥ integrations cause cancellation, the dropped term can be comparable to the signal. The manuscript does not quantify it. Given that the forecast SNR is a central result, this term should be estimated (e.g., with a simple perturbative model or a simulation-based power spectrum) and shown to be subdominant, or included in the signal.","section":"App. A.3, Eq. (A.4)–(A.5)"},{"comment":"The translation of total SNR into 'precision on the matter power spectrum' is too schematic. It uses ≈2(Ω_b/Ω_m)/SNR, which assumes P_bm/P_mm ≈ 1 and a single effective scale, while the SNR is integrated over ℓ and over all bin pairs, i.e., over a range of k and z. The resulting constraint on the baryonic suppression is a weighted average with a model-dependent shape (here Battaglia AGN). Please express the forecast as a constraint on P_em bandpowers (or on a specified amplitude of the suppression in k bins), and state clearly that the percent-level numbers are statistical only, before systematic terms such as P_em/P_bm are added.","section":"§5.1, §5.3, Fig. 2"},{"comment":"The forecast relies on the snapshot approximation: P_em and P_vrvr are evaluated at the kernel peak redshifts, while the nulled kernels have widths 355–977 Mpc. The appendix itself notes that this assumption 'may not be accurate on non-linear scales if the redshift bin is very wide.' The covariance is also Gaussian and drops non-Gaussian contributions and the K–V cross-term. None of these approximations is tested or assigned an uncertainty. For a paper claiming sub-percent precision with CMB-HD, these choices need validation (e.g., comparing to a light-cone computation or using non-Gaussian covariance from simulations), or the precision claims should be softened to reflect the systematic uncertainty.","section":"§4.3, §5.1, App. A"}],"minor_comments":[{"comment":"There is a typo: 'The kSZ effect is one such probe that traces the electron distribution directly is the kSZ effect.' The duplicated phrase should be removed.","section":"§1, first paragraph"},{"comment":"Please clarify in the caption that the right-axis precision is the statistical precision under the P_em = P_bm and P_bm/P_mm = 1 assumptions; as written, it may be misread as an unconditional forecast.","section":"Fig. 2"},{"comment":"The notation H^v_α(χ) uses χ′ in the velocity integral but is written as a function of χ; align the variables to avoid confusion.","section":"Eq. (4.1)"},{"comment":"The section is titled 'Full covariance' but the covariance is Gaussian and explicitly ignores the K–V cross-term; rename or caveat to avoid overstating the completeness.","section":"§5.1"},{"comment":"The sentence about [73] appearing 'the same week' is better placed in a footnote or removed; in a refereed paper, contemporaneous related work is usually cited without the submission-time remark.","section":"§1, references to [73]"},{"comment":"The toy model assumes ⟨δ1δ2⟩ = 0 for Δχ > 100 Mpc; this is a strong assumption and should be stated as such in the main text when using the optimum width.","section":"App. B.1"}],"recommendation":"major_revision","confidential_remarks":"The proposed estimator is novel and likely of interest to the cosmology community. The central derivation and forecast are clearly presented, and the appendices are useful. The key issue is not the analytic machinery but the physical interpretation: the P_em ≈ P_bm mapping and the dropped δ_e–v_r term need to be addressed before the claims about matter power spectrum constraints are reliable. If the authors provide a simulation-based quantification, the paper could be acceptable; otherwise the claims should be scaled back to P_em measurements. No concerns about the citation pattern or novelty disclosure."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Read the Ganguly et al. shear×kSZ forecast. The core idea is clean: build a kSZ template by multiplying weak-lensing convergence with a reconstructed radial velocity field, cross-correlate with CMB temperature, and you get a direct handle on the electron–matter power spectrum P_em without ever needing to model the galaxy–halo connection. Replacing one galaxy field in the usual ⟨ggT⟩ estimator with shear is genuinely new — the closest prior art uses galaxy overdensity, and the same-week paper [73] is acknowledged. The analytic derivation of Eq. (4.3) in App. A is coherent, and the forecasts are sensible: SNR ~5–15 for ACT/SO, >100 for CMB-HD, with realistic survey specs and a reasonable Gaussian covariance. The BNT nulling to localize kernels in redshift is a nice touch, and the paper is honest about its approximations — the snapshot assumption is flagged in App. A, and the velocity-reconstruction noise limitations are discussed.\n\nThe soft spots are in the interpretation rather than the estimator. The headline precision on the baryonic suppression of the matter power spectrum rests on Eq. (3.3), which assumes P_em ≈ P_bm — that free electrons trace all baryons. That is stated but not tested. On the scales where feedback matters (k≳1 h/Mpc), stars and cold gas contribute to P_bm but not to P_em, and the electron distribution can differ from the total baryon distribution. If P_em/P_bm deviates by a few percent, the inferred suppression is biased by an amount comparable to the claimed statistical precision. The paper does not quantify this ratio from simulations or propagate its uncertainty. Relatedly, the conversion of SNR to precision on the suppression is a one-liner — 2(Ω_b/Ω_m)/SNR — not a full Fisher forecast, and it ignores the fact that the template only partially correlates with the true kSZ (r ~ 0.05). The estimator still measures P_em, which is useful in its own right, but the connection to P_mm suppression needs validation.\n\nAlso minor: the snapshot approximation for the wide nulled kernels (977 Mpc for Rubin) could introduce errors in the non-linear power spectra, as the paper itself concedes. And no code or data are shipped, so I cannot verify the numerical integrations or the Battaglia profile, but the method is specified in enough detail to re-implement.\n\nOverall, this is a solid forecast paper with a genuinely new estimator and an honest treatment of its limitations. The central idea holds up as an estimator of P_em; the interpretation in terms of few-percent constraints on baryonic suppression is the part that needs support. I'd send it to a referee — the estimator deserves to be in the literature, and the referee can push on the P_em≈P_bm assumption. I would cite it, though for the estimator rather than the headline constraints. For a reading group, it's worth a slot, mainly to discuss how much the interpretation can be salvaged.\n\nRecommendation: send to peer review.","headline":"New estimator, clean and honest, but the headline precision claim rests on an unvalidated P_em≈P_bm mapping.","tokens_in":27736,"tokens_out":3229,"would_cite":true,"duration_ms":31416,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Replacing galaxies with weak-lensing convergence in a kSZ template yields a cross-correlation directly sensitive to the electron–matter power spectrum, giving few-percent to sub-percent constraints on baryonic feedback without modeling the","keywords":["kinetic Sunyaev-Zeldovich effect","weak lensing convergence","baryonic feedback","matter power spectrum","velocity reconstruction","nulling transform","cosmic shear","CMB cross-correlation"],"falsifier":"In a hydrodynamical simulation box where the electron–matter and baryon–matter power spectra are known, compute the ratio $P_{em}/P_{bm}$ at $z\\approx 0.5$ and $k\\approx 1\\,h/\\mathrm{Mpc}$. If this ratio deviates from unity by more than the claimed few-percent precision, the method's translation from $P_{em}$ to the baryonic suppression of the matter power spectrum is invalid.","tokens_in":26689,"feed_emoji":"🔭","tokens_out":5445,"duration_ms":52607,"temperature":0.7,"texified_at":"2026-08-05T21:54:38.143394+00:00","pith_summary":"This paper proposes a new way to measure how baryonic feedback suppresses the small-scale matter power spectrum, the leading unknown for upcoming weak-lensing surveys. Instead of stacking the kSZ signal on galaxies, which requires modeling how galaxies trace dark matter, the authors multiply tomographic weak-lensing convergence maps by radial velocity maps reconstructed from galaxy surveys to build a kSZ template, then cross-correlate it with the CMB temperature. The resulting signal is directly proportional to the electron–matter power spectrum, so a clean measurement yields the baryonic contribution to cosmic shear without a galaxy–matter model. Forecasting for two weak-lensing surveys with three CMB experiments, they find signal-to-noise of 5–15 for current and upcoming CMB data and above 100 for a future CMB-HD survey, corresponding to few-percent and sub-percent constraints, respectively, on the baryonic suppression of the matter power spectrum.","texify_model":"deepseek-v4-flash","texify_usage":{"total_tokens":7241,"prompt_tokens":818,"completion_tokens":6423,"prompt_tokens_details":{"cached_tokens":0},"prompt_cache_hit_tokens":0,"prompt_cache_miss_tokens":818,"completion_tokens_details":{"reasoning_tokens":5696}},"feed_headline":"Baryon suppression measured to sub-percent via shear-kSZ","feed_subtitle":"Replacing galaxies with lensing convergence in a kSZ template avoids galaxy-halo modeling.","key_machinery":"The central object is the template kSZ estimator $\\hat{T}_{i,\\alpha}=K_i V_\\alpha$, the product of a tomographic weak-lensing convergence map and a radial-velocity map reconstructed from galaxy positions via the linearized continuity equation. Cross-correlating this template with the observed CMB temperature yields a signal whose leading term is $P_{em}$ multiplied by the velocity power spectrum (Eq. 4.3). The BNT nulling transform, a linear combination of three adjacent lensing kernels that cancels low-redshift contributions, localizes the measurement in comoving distance. An important secondary mechanism is the decomposition of the matter power spectrum $P_{mm}$ into dark-matter and","core_discovery":"The central claim is that the cross-correlation between the CMB temperature and a template $\\hat{T}_{i,\\alpha}=K_i V_\\alpha$, formed by multiplying the weak-lensing convergence in redshift bin $i$ with a radial-velocity map reconstructed in bin $\\alpha$, isolates the kinetic Sunyaev-Zeldovich signal and measures the electron–matter power spectrum $P_{em}(k,z)$ nearly directly (Eq. 4.3). Because the template is linear in the line-of-sight velocity and in the observed temperature, primary CMB and foregrounds average away; because the convergence field traces total matter rather than galaxies, no galaxy–halo connection needs to be modeled. Applying the BNT nulling transform localizes th","pith_inferences":["The few-percent calibration implicitly assumes free electrons trace baryons; a useful cross-check would be comparing the shear–kSZ template signal with pairwise kSZ measurements around galaxy clusters, where the gas profile is independently known.","The same template construction could be extended to other gas tracers, such as fast radio burst dispersion measures or X-ray gas maps, potentially providing independent handles on the same baryonic suppression.","A practical refinement would be to use a dedicated low-redshift spectroscopic sample for velocity reconstruction, which the paper suggests but does not quantify; this would recover the missing leverage for Roman at z<0.5.","The correlation coefficient between template and true kSZ is only about 0.04–0.06, so this estimator is not suited to cleaning kSZ from CMB maps; the paper's own forecasts do not require such cleaning."],"forward_implications":["A detection is predicted at about 5σ for Rubin with ACT and 10σ for Roman with ACT, so the signal should be measurable with data already being collected.","With the Simons Observatory the same method reaches SNR around 8–15, enough to constrain baryonic feedback at the few-percent level required for Rubin-era cosmic shear.","With CMB-HD the SNR exceeds 100, giving sub-percent constraints on the baryonic suppression of the matter power spectrum.","Because the estimator uses convergence instead of a galaxy overdensity field, it sidesteps the galaxy–matter connection, assembly bias, and halo miscentering that complicate existing kSZ–galaxy analyses.","The nulling transform makes the measurement redshift-localized, so the redshift evolution of feedback can in principle be mapped."],"fun_headline_variants":["Shear-kSZ isolates baryons without galaxy modeling","kSZ template from lensing, not galaxies","Sub-percent baryon suppression via shear-kSZ","Galaxy-free kSZ measures feedback to 1%","Shear-kSZ cuts baryon systematics for Rubin"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The conversion of the measured electron–matter power spectrum into a constraint on baryonic suppression assumes that free electrons faithfully trace all baryons and that the neglected baryon–baryon term stays at its $O((\\Omega_b/\\Omega_m)^2)\\approx 1.7\\%$ level; on the small scales where feedback is strongest, the ionized gas distribution may depart from the total baryon distribution.","fun_headline_variants_meta":{"raw":{"variants":["Shear-kSZ isolates baryons without galaxy modeling","kSZ template from lensing, not galaxies","Sub-percent baryon suppression via shear-kSZ","Galaxy-free kSZ measures feedback to 1%","Shear-kSZ cuts baryon systematics for Rubin"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000118,"raw_usage":{"total_tokens":926,"prompt_tokens":757,"completion_tokens":169,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":501,"completion_tokens_details":{"reasoning_tokens":102}},"tokens_in":501,"tokens_out":169,"duration_ms":2859,"temperature":1.0,"reasoning_tokens":102,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-03T13:48:16.288479+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"In a hydrodynamical simulation box where the electron–matter and baryon–matter power spectra are known, compute the ratio $P_{em}/P_{bm}$ at $z\\approx 0.5$ and $k\\approx 1\\,h/\\mathrm{Mpc}$. If this ratio deviates from unity by more than the claimed few-percent precision, the method's translation from $P_{em}$ to the baryonic suppression of the matter power spectrum is invalid.","supporting_citations":[],"review_version":1}