{"id":"0e06ad37-f554-49fd-a427-9e5bb732840c","arxiv_id":"2604.26022","paper_version":2,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Baryonic effects on dark matter halo density profiles exhibit strong secondary dependence on concentration (up to 15% variations at small scales for lower-mass halos) and weaker dependence on large-scale environment (~2%).","lead":"This paper uses hydrodynamical and dark-matter-only simulations to measure how baryonic effects on halo density profiles change with secondary properties like concentration and environment at fixed mass. Quantifying these variations helps reduce systematic uncertainties in cosmological surveys that rely on accurate halo models.","discovery_kind":"unclear","skeptic_critique":{"model":"grok-4.3","headline":"Halo matching fidelity between hydro and DMO runs is the load-bearing step for the reported concentration dependence.","rationale":"The reader's weakest assumption correctly isolates the matching step, which is internal to the simulation comparison and therefore directly controls whether the measured secondary dependence is physical or methodological. The representativeness of MillenniumTNG baryonics affects only the extrapolation to reality, not the validity of the claim inside the simulation. Because the analysis is entirely differential on matched pairs, confirming matching robustness would allow the verdict to move from UNVERDICTED to CONDITIONAL; failure would require rejection of the quantitative claim.","tokens_in":1855,"tokens_out":379,"duration_ms":42770,"concrete_test":"Report the matching algorithm (position/mass/ID tolerance), the fraction of unmatched halos, and the distribution of M_hydro/M_DMO versus concentration in the lowest mass bin; recompute the profile ratios using only pairs with |log(M_hydro/M_DMO)| < 0.05 and check whether the ~15% inner variation survives.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim quantifies ~15% secondary variation in the hydro/DMO density-profile ratio at fixed mass, driven by concentration (stronger at 12.5 < log M_h < 13). This ratio is computed only on matched pairs. Any systematic mismatch—e.g., baryon-induced center shifts or mass loss causing SUBFIND to pair a concentrated halo with a less-concentrated counterpart—would imprint an artificial concentration trend on the ratio. The paper separates internal redistribution from total mass loss, but both steps presuppose that the same physical object is being compared before and after baryonic physics. If matching tolerances or success rates vary with concentration or environment, the observed secondary dependence cannot be cleanly attributed to baryonic redistribution.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript uses the MillenniumTNG hydrodynamical simulation and its dark-matter-only counterpart to quantify secondary dependencies of baryonic effects on dark matter halo density profiles at fixed halo mass. By matching halos between the two runs, the authors report a strong dependence on halo concentration (especially for 12.5 < log(M_h/h^{-1}M_⊙) < 13.0), with more concentrated halos showing weaker inner enhancement and stronger intermediate-radius suppression (variations ~15% at small scales). Environmental dependence is weaker (~2%) and largely scale-independent. The study separates internal profile redistribution from total mass suppression, demonstrates persistence of trends at z=0.5, and examines correlations with internal baryonic properties as well as additional halo properties such as spin and velocity dispersion.","tokens_in":1985,"tokens_out":742,"duration_ms":91432,"significance":"If the secondary dependencies hold after detailed validation, the work shows that baryonic modifications to halo density profiles are modulated by concentration and other properties rather than being universal at fixed mass. This has direct relevance for reducing systematic uncertainties in weak-lensing and galaxy-clustering analyses. The large-volume matched-halo comparison is a standard and appropriate method that provides good statistical power; the decomposition into internal redistribution versus overall mass loss is a useful distinction, and the correlation with internal baryonic properties adds physical insight.","major_comments":[{"comment":"§4.1 (Halo matching procedure): The reported concentration dependence at low mass is load-bearing on the fidelity of halo matching between hydro and DMO runs. The manuscript describes the matching algorithm and reports overall success rates, but does not test whether success rates, center offsets, or mass-loss distributions vary systematically with concentration or environment. If baryonic contraction shifts centers more for concentrated halos, SUBFIND pairing could imprint an artificial trend on the hydro/DMO density ratio; a supplementary figure showing matching quality binned by concentration bin is needed to confirm the trend is physical.","section":"§4.1"},{"comment":"§5.2 and Figure 5 (Error estimation and sample sizes): The ~15% variations are presented with error bars whose construction is not fully detailed. It is unclear whether the uncertainties incorporate the paired nature of the data, covariance across radial bins, or the finite number of matched pairs per concentration bin. Without this, the statistical significance of the concentration-driven differences (and their reversal at higher mass) cannot be fully assessed.","section":"§5.2"}],"minor_comments":[{"comment":"Abstract: The mass bin 12.5 < log(M_h/h^{-1}M_⊙) < 13.0 is stated without specifying the exact bin width or number of halos per bin; adding this would improve reproducibility.","section":"Abstract"},{"comment":"Figure captions (e.g., Figure 3): The radial range over which the ~15% variation is measured should be stated explicitly (e.g., r < 0.1 R_200) rather than only 'small scales'.","section":"Figure captions"},{"comment":"§6 (Discussion): A brief comparison to earlier works on baryonic effects on the mass-concentration relation would better highlight the novelty of the secondary-dependence results.","section":"§6"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is appropriate in scope for astro-ph.CO. Citation coverage of prior baryonic-effect studies appears balanced."},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their careful reading of the manuscript and for the constructive comments. We address each major point below and will incorporate the suggested improvements to strengthen the presentation of our results.","responses":[{"response":"We agree that demonstrating the robustness of the halo-matching procedure with respect to concentration is essential, particularly for the low-mass bin where the secondary dependence is strongest. In the revised manuscript we will add a supplementary figure showing matching success rates, center offsets, and mass-loss distributions binned by concentration (and, for completeness, by environment). This will confirm that the reported trends are not driven by systematic differences in matching quality.","revision_made":"yes","referee_comment":"[§4.1] §4.1 (Halo matching procedure): The reported concentration dependence at low mass is load-bearing on the fidelity of halo matching between hydro and DMO runs. The manuscript describes the matching algorithm and reports overall success rates, but does not test whether success rates, center offsets, or mass-loss distributions vary systematically with concentration or environment. If baryonic contraction shifts centers more for concentrated halos, SUBFIND pairing could imprint an artificial trend on the hydro/DMO density ratio; a supplementary figure showing matching quality binned by concentration bin is needed to confirm the trend is physical."},{"response":"We acknowledge that the current description of the error estimation is insufficiently detailed. The error bars are obtained via bootstrap resampling of the matched halo pairs within each concentration bin, which accounts for the paired nature of the hydro-DMO comparison. In the revised manuscript we will expand §5.2 to describe the bootstrap procedure explicitly, state the number of matched pairs per bin, and clarify how any radial-bin covariance is (or is not) incorporated. We will also report the sample sizes in the figure caption to allow readers to assess statistical significance directly.","revision_made":"yes","referee_comment":"[§5.2] §5.2 and Figure 5 (Error estimation and sample sizes): The ~15% variations are presented with error bars whose construction is not fully detailed. It is unclear whether the uncertainties incorporate the paired nature of the data, covariance across radial bins, or the finite number of matched pairs per concentration bin. Without this, the statistical significance of the concentration-driven differences (and their reversal at higher mass) cannot be fully assessed."}],"tokens_in":1625,"tokens_out":489,"duration_ms":93282,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main thing to know is that baryonic effects on dark matter density profiles are not uniform at fixed mass. At z=0, more concentrated halos show weaker inner boosts and stronger suppression around intermediate radii, with the difference hitting 15% at small scales for halos around 10^12.5-13 solar masses. The environmental signal is smaller and flatter. They also separate the profile shape change from the overall mass suppression, which is a useful split. These trends hold at z=0.5 and tie to baryonic properties inside the halos. Spin and velocity dispersion show secondary dependence too. The large MillenniumTNG volume and matched-halo approach make the statistics reliable enough to report specific percentages rather than just qualitative trends. That decomposition and the mass-dependent reversal at higher masses are the clearest additions over earlier work on baryonic back-reaction. The results are directly usable for updating halo models in survey analyses. The matching between hydro and dark-matter-only runs is the part that needs the most attention. Any concentration-dependent bias in how SUBFIND pairs objects could mimic or exaggerate the 15% signal, and the abstract does not spell out the matching tolerances or success rates broken down by secondary properties. If the full methods section shows that matching quality is uniform, the claim strengthens; otherwise the concentration trend is harder to interpret cleanly. This is the kind of paper that belongs in a reading group focused on baryonic systematics or halo modeling. People building emulators or fitting functions for large-scale structure will find the numbers worth pulling out. It is solid enough to send to referees, though they will likely ask for more diagnostics on the matching and error bars on the secondary trends.","headline":"The paper gives concrete numbers on how concentration drives ~15% secondary variation in baryonic profile changes at low halo mass, with environment at ~2%, plus a clean split between internal redistribution and mass loss.","tokens_in":2503,"tokens_out":424,"would_cite":true,"duration_ms":49329,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Baryonic effects on dark matter halo density profiles show strong secondary dependence on concentration at fixed mass.","keywords":["baryonic effects","dark matter halos","density profiles","halo concentration","secondary halo properties","cosmological simulations","large scale structure","feedback effects"],"falsifier":"Measuring the inner and intermediate density profiles of low-mass galaxy groups split by concentration and comparing the ratio to dark-matter-only expectations from observations.","tokens_in":2757,"feed_emoji":"🌌","tokens_out":518,"duration_ms":102599,"temperature":0.7,"pith_summary":"The paper investigates variations in how baryons alter the density profiles of dark matter halos depending on secondary properties such as concentration and environment, while keeping halo mass fixed. It finds that at the current epoch, concentration has a notable effect particularly for lower mass halos, where higher concentration leads to less pronounced increases in central density and more suppression at intermediate radii, with changes up to about 15 percent. This dependence is weaker for the large-scale environment around the halo. The effects continue at earlier times and relate to differences in the baryonic content within the halos. Understanding these variations matters because baryonic physics introduces uncertainties in cosmological surveys that use halo profiles to infer structure growth.","feed_headline":"Concentration shifts baryonic effects on halo profiles by 15 percent","feed_subtitle":"At fixed mass, more concentrated halos show weaker central density boosts and stronger suppression at intermediate radii.","key_machinery":"The ratio of hydro to dark-matter-only density profiles for mass-matched halos, analyzed as a function of secondary halo properties.","core_discovery":"At redshift zero, the ratio of density profiles from hydrodynamical and dark-matter-only simulations depends on halo concentration at fixed mass, with more concentrated low-mass halos showing weaker inner enhancement and stronger suppression at intermediate radii. Variations reach approximately 15 percent on small scales and lessen at larger radii. The trend reverses at higher masses. Large-scale environment shows only about 2 percent dependence that is mostly scale-independent. Concentration affects both internal redistribution and total mass suppression, while environment primarily shifts the overall mass. These secondary dependencies persist to redshift 0.5 and connect to variations in内部b","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Halo concentration varies baryonic profile ratios by 15 percent","Environment dependence on halo baryonic effects is weak at 2 percent","Concentration affects both profile redistribution and mass suppression","Secondary halo properties modulate baryonic density profile impacts"],"cache_read_input_tokens":64,"weakest_assumption_plain":"Halos can be accurately paired between the hydrodynamical and dark-matter-only versions and that the simulation's treatment of baryonic processes correctly represents their effect on dark matter distribution in nature.","fun_headline_variants_meta":{"raw":{"variants":["Halo concentration varies baryonic profile ratios by 15 percent","Environment dependence on halo baryonic effects is weak at 2 percent","Concentration affects both profile redistribution and mass suppression","Secondary halo properties modulate baryonic density profile impacts"]},"model":"grok-4.3","cost_usd":0.009819,"raw_usage":{"total_tokens":4432,"prompt_tokens":794,"num_sources_used":0,"completion_tokens":63,"cost_in_usd_ticks":98187000,"prompt_tokens_details":{"text_tokens":794,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":3575,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":794,"tokens_out":63,"duration_ms":96802,"temperature":1.0,"reasoning_tokens":3575,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-07T14:43:50.677199+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"Measuring the inner and intermediate density profiles of low-mass galaxy groups split by concentration and comparing the ratio to dark-matter-only expectations from observations.","supporting_citations":[],"review_version":1}