{"id":"356c6d00-409b-474f-8dd8-96600dca0c12","arxiv_id":"2505.18258","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Baryonic feedback imprints on cosmological observables are governed by halo mass assembly: feedback is most efficient at M200m around 10^12.8 solar masses regardless of redshift.","lead":"The paper shows that different cosmological probes of galaxy feedback, such as tSZ, weak lensing, X-ray and kSZ measurements, see very different halo populations at different masses and redshifts. It uses the FLAMINGO simulations to argue that feedback is most efficient at a characteristic halo mass around 10^12.8 solar masses, helping reconcile apparently conflicting feedback measurements.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"kSZ halo masses rely entirely on FLAMINGO SMHM; a >0.3 dex systematic offset would erase the claimed population separation and the reconciliation of feedback constraints.","rationale":"The reader identified the same premise, and I agree it is the weakest. I considered two other candidates: (1) the redshift-independence of the characteristic feedback mass 10^12.8 Msun is measured only in FLAMINGO, but the paper explicitly invites generalization and this claim is not needed for the probe-separation argument; (2) the kSZ sensitivity proxy (number density weighted by gas mass in a 3 Mpc aperture) is an approximation, but the authors checked aperture stability and the proxy is secondary to the mass assignment. The SMHM issue is more load-bearing because the entire reconciliation narrative depends on the DESI LRG halos being a distinct, lower-mass population. The tSZ, WL, and eROSITA footprints are anchored to observables (class_sz halo model, survey scale-cuts, actual X-ray catalog masses), whereas the kSZ footprint is entirely generated from FLAMINGO's empirical galaxy-halo relation with no external calibration in this paper. The 0.1-0.2 dex robustness check is not a bound on systematic error; it is a sensitivity estimate. Therefore the verdict should remain conditional: the qualitative conclusions are plausible and novel, but acceptance of the reconciliation claim should be contingent on an independent halo mass calibration for the kSZ sample.","tokens_in":31337,"tokens_out":5276,"duration_ms":48335,"concrete_test":"Assign host halo masses to the same DESI Legacy DR9 LRG stellar masses using an independent SMHM relation calibrated to clustering or lensing, e.g., the DESI HOD of Yuan et al. (2024) or the galaxy-galaxy lensing masses of McCarthy et al. (2024), including scatter and the 11% satellite population. Recompute the kSZ sensitivity points in Fig. 3 and measure the fraction of LRGs with M200m > 10^14 Msun and the overlap fraction of the kSZ footprint with the eROSITA/tSZ/WL contours. If the >10^14 fraction exceeds 10%, the distinct-population interpretation is not robust.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central two-population claim rests on the DESI LRG halo masses used to place the kSZ sensitivity footprint in Fig. 3. In Sec. IV E, each LRG is assigned a host halo mass by sampling the stellar-mass-to-halo-mass relation of central galaxies in the FLAMINGO fiducial simulation at z=0.7. The paper states the inferred mean mass (10^13.1-13.3 Msun) can shift by 0.1-0.2 dex due to SMHM prescription or satellite contamination, and the internal satellite test covers only the 11% satellite fraction. A systematic offset of 0.3-0.5 dex in the SMHM normalization or slope, which is within the range of differences among published SMHM relations, would move the kSZ population to M200m ~ 10^13.5-13.8 Msun and into overlap with the eROSITA and weak-lensing footprints. Since the reconciliation of kSZ-driven strong-feedback constraints with X-ray-derived weak-feedback constraints is the paper's central application, this single assumption is the most load-bearing link in the argument.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reframes baryonic feedback effects on cosmological observables in terms of halo mass assembly histories rather than the usual matter power spectrum suppression. Using analytic halo-model sensitivity calculations (tSZ power spectrum, weak-lensing two-point functions, eROSITA cluster counts) and matched hydrodynamical/gravity-only FLAMINGO simulations, it maps which halo mass and redshift populations each observable probes, and how feedback modifies the baryonic and gas content of those halos over time. The central claims are: (i) the tSZ, X-ray, and weak-lensing probes jointly target high-mass clusters (M200m ~ 10^15 Msun at z<1); (ii) stacked kSZ measurements of DESI LRGs target a distinct lower-mass population (M200m ~ 10^13.1-13.3 Msun at z ~ 0.4-1); and (iii) feedback most efficiently redistributes baryons when halos reach M200m ~ 10^12.8 Msun, independent of redshift, becoming ineffective by M200m ~ 10^15 Msun. These results are used to reconcile apparently strong kSZ-derived feedback constraints with weaker X-ray-derived constraints, and to suggest lensing analysis strategies that minimize feedback sensitivity.","tokens_in":31513,"tokens_out":2653,"duration_ms":26889,"significance":"If the central two-population picture holds, the paper provides a genuinely useful physical organizing principle for interpreting disparate feedback constraints: different observables simply see different stages of halo assembly. The analytic sensitivity maps (Figs. 1-3) follow standard halo-model practice, agree with previous work (e.g., To et al. 2024, Komatsu & Seljak 2002), and are clearly presented. The simulation analysis benefits from careful halo matching between hydrodynamical and gravity-only runs, from the use of multiple FLAMINGO feedback variations, and from treatment of several radial definitions (R500c, R200m, 5xR500c). The paper also offers concrete, falsifiable predictions: kSZ and X-ray/lensing constraints need not agree because they probe different populations, and lensing scale cuts such as DES's should suppress one-halo feedback sensitivity. The main significance risk is that the quantitative claims—the 10^12.8 Msun characteristic mass and the separation of the kSZ population—rest on a single simulation suite and on a stellar-mass-to-halo-mass assignment for DESI LRGs that is not independently calibrated to the kSZ host halos.","major_comments":[{"comment":"The kSZ halo-mass population is assigned entirely through the FLAMINGO fiducial stellar-mass-to-halo-mass relation at z=0.7. The paper states that the mean inferred mass can shift by 0.1-0.2 dex depending on the SMHM prescription and satellite fraction, but this range appears to cover only the internal variations discussed, not the full spread among published SMHM relations (e.g., Behroozi et al. 2010, Moster et al. 2010). A systematic offset of 0.3-0.5 dex in SMHM normalization or slope would move the mean kSZ halo mass to log M200m ~ 13.5-13.8, overlapping the eROSITA and weak-lensing footprints. Since the reconciliation of kSZ and X-ray constraints is the central application of this paper, the authors should quantify the robustness of the population separation under alternative SMHM relations (including abundance matching and galaxy-galaxy lensing mass estimates) or explicitly show what magnitude of SMHM offset would erase the separation.","section":"Sec. IV E and Fig. 3"},{"comment":"The claim that feedback is most efficient at M200m ~ 10^12.8 Msun 'regardless of redshift' is measured only within the FLAMINGO subgrid models. The paper itself acknowledges in Sec. V C that 'It would be interesting to check the extent to which these findings generalize to different simulation suites.' This is a load-bearing assumption for the paper's central unifying narrative. I recommend either (a) testing the same instantaneous-mass scaling in at least one independent simulation suite or semi-empirical model, or (b) explicitly reframing the conclusion as a FLAMINGO-based result and discussing how the characteristic mass might shift under different feedback implementations beyond the fgas-8sigma and jet-AGN variants shown.","section":"Sec. V C and Fig. 5"},{"comment":"All quantitative statements about feedback impact (e.g., 5-10% mass suppression at 2<z<4 for clusters, 5-20% for lower-mass halos) are based on median histories only, with no scatter or uncertainty bands shown. Since the matched halo samples for the M200m ~ 10^15 Msun population are necessarily small, and since the conclusion that high-mass clusters are 'largely insensitive' is a strong quantitative claim, the paper should report at least the interquartile range or bootstrap uncertainties for the ratios in Figs. 4-7, or state the sample sizes that justify the median as a representative statistic.","section":"Sec. V B and Figs. 4-7"}],"minor_comments":[{"comment":"The definition of sensitivity as the second derivative d^2 C_l / (dz d lnM) is a response density rather than a probability distribution, so the 33% and 66% contour levels in Fig. 1 are somewhat arbitrary. It would help to state explicitly that these contours are normalized to the peak of this density and that they do not integrate to a fixed fraction of the total signal by construction.","section":"Sec. IV B, Eq. (3)"},{"comment":"The notation dP1h/dM and dP2h/dM in Eq. (7) is used before defining them in Eqs. (8)-(9); reordering the equations or adding a sentence of orientation would improve readability.","section":"Sec. IV C, Eq. (7)"},{"comment":"The caption says 'Left panel' and 'Right panel' but the figure actually contains two groups of three rows each; the text should refer to 'left column' and 'right column' to avoid confusion, and the panel labels in the figure itself would help.","section":"Fig. 6 caption"},{"comment":"The middle panel is described as probing R500c of high-mass clusters, but the text says 'inner regions of groups' in one place; please align the wording (groups vs. clusters) with the mass range shown in the panel.","section":"Sec. V D, Fig. 7"}],"recommendation":"major_revision","confidential_remarks":"The paper is well within the scope of a cosmology journal and the analytic framework is sound. The main risk is that the two-population reconciliation and the characteristic feedback mass are presented as general results although they depend on the FLAMINGO SMHM and subgrid calibration; if the authors can add robustness tests against external SMHM relations and an explicit discussion of model dependence, the paper would be a solid contribution. I recommend major revision rather than rejection because the issues are addressable within the manuscript's scope."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The headline: this paper gives the clearest demonstration yet that stacked kSZ measurements and tSZ/X-ray/lensing probes are looking at different halo populations at different stages of assembly, and that this reconciles the apparent tension between strong-feedback kSZ constraints and weak-feedback X-ray constraints. The new piece is the unified sensitivity map (Fig. 3) and the redshift-independent characteristic mass ~10^12.8 M_sun where feedback most efficiently redistributes baryons. The analytic part follows standard halo-model practice and checks out; the simulation analysis is carefully matched between hydro and DMO, and the authors are honest about the caveats.\n\nSoft spots: The two-population claim depends on the FLAMINGO SMHM used to assign halo masses to DESI LRGs. The paper states a 0.1-0.2 dex shift from prescription or satellites. The stress-test worry is that a 0.3-0.5 dex offset could move the kSZ population into overlap with eROSITA and WL. I think that's overstated: even at 0.5 dex, the kSZ population sits at 10^13.5-14.0 at z~0.5-1, still a dex below the tSZ peak and mostly disjoint in redshift from the low-z WL/eROSITA signals. It would blur the clean two-population picture, not erase it. The bigger limitation is that the characteristic mass 10^12.8 is measured from one simulation suite (FLAMINGO) with its subgrid choices; the authors acknowledge this, and it is a testable prediction rather than a fatal flaw. Also, the median assembly histories in Figs 4-6 are shown without scatter or uncertainty bands; that's a minor presentational issue, the trends look robust.\n\nWho it's for: anyone working on baryonic feedback constraints, kSZ stacking, or lensing systematics. It deserves a serious referee; the synthesis is novel and the analysis is careful. I'd send it out.","headline":"A careful synthesis showing kSZ and tSZ/X-ray/lensing probes target different halo populations, reconciling conflicting feedback constraints; the main caveat is the FLAMINGO-based halo mass assignment for LRGs, which is real but not fatal.","tokens_in":32101,"tokens_out":2858,"would_cite":true,"duration_ms":25257,"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":"The paper claims that baryonic feedback redistributes gas most efficiently when halos reach $M_{200\\mathrm{m}}\\simeq 10^{12.8}\\,\\mathrm{M}_\\odot$, regardless of redshift, and that this single mass scale resolves apparent conflicts between…","keywords":["baryonic feedback","halo assembly histories","kinetic Sunyaev-Zel'dovich effect","thermal Sunyaev-Zel'dovich effect","weak lensing","X-ray galaxy clusters","FLAMINGO simulations","halo mass function sensitivity"],"falsifier":"Measure the halo masses of the same DESI LRG sample with galaxy-galaxy lensing; if the mean $M_{200\\mathrm{m}}$ comes out above roughly $10^{13.5}\\,\\mathrm{M}_\\odot$ or overlaps the $\\sim10^{15}\\,\\mathrm{M}_\\odot$ cluster population, the two-population separation collapses. Alternatively, run an independent hydrodynamical simulation suite and check whether the minimum of the gas-to-total mass ratio stays at $M_{200\\mathrm{m}}\\simeq10^{12.8}\\,\\mathrm{M}_\\odot$ at every redshift.","tokens_in":31136,"feed_emoji":"🌌","tokens_out":6632,"duration_ms":55187,"temperature":0.7,"pith_summary":"This paper argues that the impact of galaxy-formation feedback on cosmology is best understood through halo mass assembly histories rather than the usual suppression of the matter power spectrum. By computing which halo masses and redshifts each probe actually sees, the authors find two distinct halo populations: tSZ, X-ray, and weak-lensing measurements mostly see massive clusters near $10^{15}\\,\\mathrm{M}_\\odot$ at $z<1$, while stacked kSZ measurements of DESI luminous red galaxies see lower-mass halos near $10^{13.1}\\,\\mathrm{M}_\\odot$ at $z\\sim0.5$-$1$. The central discovery is that feedback most efficiently removes baryons when a halo crosses $M_{200\\mathrm{m}}\\simeq10^{12.8}\\,\\mathrm{M}_\\odot$, independent of when in cosmic history that happens, and becomes negligible by $10^{15}\\,\\mathrm{M}_\\odot$ as ejected gas is re-accreted. This explains why kSZ observations appear to demand strong feedback while X-ray, lensing, and tSZ observations do not: they are probing different halo populations at different stages of assembly.","feed_headline":"One halo mass sets feedback strength at every redshift","feed_subtitle":"The same halos seen by tSZ, X-rays and lensing sit at a different mass than kSZ galaxies, ending a feedback conflict","key_machinery":"The central object is the halo mass assembly history (MAH), the track of a halo's mass over time supplied by following self-bound structures across simulation snapshots. Halos in hydrodynamical runs are matched to their counterparts in gravity-only runs through the ten most strongly bound particles, so the same objects can be compared with and without feedback. The argument then uses gas and baryon mass fractions in three apertures ($R_{500c}$, $R_{200m}$, and $5R_{500c}$) as functions of both present-day mass and instantaneous mass; the key identity is the universal trough in gas fraction at $M_{200\\mathrm{m}}\\sim10^{12.8}\\,\\mathrm{M}_\\odot$ seen at all redshifts, which converts assembly history into observable imprints.","core_discovery":"The paper's central claim is that baryonic feedback redistributes baryons most efficiently at a single characteristic halo mass, $M_{200\\mathrm{m}}\\simeq 10^{12.8}\\,\\mathrm{M}_\\odot$, regardless of redshift. This is established by measuring the gas mass fraction as a function of instantaneous halo mass at many redshifts in hydrodynamical simulations: every redshift shows the deepest suppression at about the same halo mass, with the exact value shifting by only 0.1-$0.3$ dex between feedback calibrations. When halos grow past $\\sim10^{14}\\,\\mathrm{M}_\\odot$ the suppression fades, and by $\\sim10^{15}\\,\\mathrm{M}_\\odot$ it is negligible because expelled gas is re-accreted. Because the thermal Sunyaev-Zel'dovich power spectrum, X-ray cluster counts, and weak-lensing one-halo terms are most sensitive to $\\sim10^{15}\\,\\mathrm{M}_\\odot$ clusters at $z\\lesssim1$, while stacked kSZ profiles of the DESI LRG sample probe $\\sim10^{13.1}\\,\\mathrm{M}_\\odot$ halos at $z\\sim0.5$-$1$, the two families of observables are measuring different halo populations; the strong feedback needed for kSZ does not contradict the weak feedback inferred from X-rays.","pith_inferences":["If the $10^{12.8}\\,\\mathrm{M}_\\odot$ trough is truly redshift-independent, baryonification and emulator models could parameterise feedback with a single characteristic mass plus a reaccretion rate, rather than fitting the full mass-redshift plane.","The 0.1-$0.2$ dex uncertainty in the inferred halo masses of the DESI LRG sample is testable with galaxy-galaxy lensing of the same galaxies; a measured mean mass near $10^{13.5}\\,\\mathrm{M}_\\odot$ or higher would seriously weaken the claim that the kSZ and cluster populations are cleanly separated.","The same reasoning implies that future kSZ stacks around lower-mass galaxies, or tSZ and lensing measurements pushed to higher redshift, should see systematically larger feedback imprints, giving observational routes to map the efficiency trough directly.","The redshift independence of the characteristic mass hints that feedback efficiency is set by a fixed potential depth or binding energy threshold, which could allow the scale to be predicted from gravitational collapse energetics rather than calibrated from simulations."],"forward_implications":["Feedback constraints from tSZ, X-ray, and weak-lensing measurements of clusters cannot be directly transferred to stacked kSZ measurements of groups, and vice versa.","The same cluster population was noticeably feedback-suppressed at $z\\sim2$-$4$, but its baryon fractions return toward the cosmic mean by $z=0$ through re-accretion, so local cluster gas fractions underestimate early feedback.","DES-style scale cuts on cosmic shear, combined with masking the rarest high-mass clusters, should keep lensing analyses close to feedback-free; explicit kernel-nulling methods should do even better.","If the low tSZ power at $\\ell>1000$ is baryonic in origin, it must come from a mechanism that lowers gas density without raising temperature, such as ejection far into the outskirts, non-thermal pressure, or more baryons locked in stars.","The intermediate halo-mass range around $M_{500}\\sim10^{13.5}$-$10^{14.5}\\,\\mathrm{M}_\\odot$ is where the fiducial simulated gas masses exceed current eROSITA estimates, matching the halo-mass range where feedback variations matter most."],"supporting_citations":[{"why":"Supplies the stacked kSZ measurements around BOSS CMASS and LOWZ halos that motivate the strong-feedback interpretation.","marker":"[16]"},{"why":"Provides the DESI LRG kSZ stacked profiles that define the lower-mass halo population central to the paper's comparison.","marker":"[17]"},{"why":"Compares kSZ and galaxy-galaxy lensing to the FLAMINGO simulations and concludes more aggressive feedback is needed, the apparent tension the paper resolves.","marker":"[19]"},{"why":"Describes the FLAMINGO simulation suite used for all hydrodynamical halo assembly histories and feedback calibrations.","marker":"[33]"},{"why":"Provides the eROSITA X-ray cluster catalog used to define the high-mass cluster population probed by X-ray counts.","marker":"[30]"},{"why":"Gives the tSZ power spectrum halo-model framework and class_sz-based sensitivity calculation used for the Planck-scale tSZ response.","marker":"[35]"},{"why":"Supplies the Tinker halo mass function used in the analytic sensitivity calculations for tSZ and weak lensing.","marker":"[65]"},{"why":"Shows that feedback has little impact on the tSZ power spectrum at low multipoles but affects higher multipoles, supporting the mass and redshift dependence found here.","marker":"[90]"}],"fun_headline_variants":["A single halo mass rules baryon feedback at all redshifts","Feedback peaks at one halo mass; fixes cosmic tension","One mass scale sets feedback: 10^12.8 solar masses","Why kSZ and X-ray views differ: halo mass matters","Feedback's sweet spot: one halo mass at every epoch"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The argument assumes that the DESI LRG galaxies used for kSZ stacks really live in halos near $M_{200\\mathrm{m}}\\sim10^{13.1}\\,\\mathrm{M}_\\odot$, as assigned by one stellar-mass-to-halo-mass relation, and that the feedback behaviour measured in this one suite of simulations carries over to the real Universe.","fun_headline_variants_meta":{"raw":{"variants":["A single halo mass rules baryon feedback at all redshifts","Feedback peaks at one halo mass; fixes cosmic tension","One mass scale sets feedback: 10^12.8 solar masses","Why kSZ and X-ray views differ: halo mass matters","Feedback's sweet spot: one halo mass at every epoch"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00036,"raw_usage":{"total_tokens":2097,"prompt_tokens":1243,"completion_tokens":854,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":859,"completion_tokens_details":{"reasoning_tokens":770}},"tokens_in":859,"tokens_out":854,"duration_ms":5788,"temperature":1.0,"reasoning_tokens":770,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T14:34:29.000443+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the halo masses of the same DESI LRG sample with galaxy-galaxy lensing; if the mean $M_{200\\mathrm{m}}$ comes out above roughly $10^{13.5}\\,\\mathrm{M}_\\odot$ or overlaps the $\\sim10^{15}\\,\\mathrm{M}_\\odot$ cluster population, the two-population separation collapses. Alternatively, run an independent hydrodynamical simulation suite and check whether the minimum of the gas-to-total mass ratio stays at $M_{200\\mathrm{m}}\\simeq10^{12.8}\\,\\mathrm{M}_\\odot$ at every redshift.","supporting_citations":[{"cited_title":"Tinker, A","cited_arxiv_id":null,"evidence_quote":"Supplies the Tinker halo mass function used in the analytic sensitivity calculations for tSZ and weak lensing."}],"review_version":1}