{"id":"5b33bb03-aa5f-4416-b3b2-3a35569711b2","arxiv_id":"2411.16849","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"In the TNG100 simulation, central galaxies in higher cold-gas vorticity environments have lower specific star formation rates at fixed halo mass.","lead":"This paper analyzes a cosmological simulation and reports that galaxies located in regions with strongly swirling cold gas tend to form stars at a lower rate, even when compared at the same halo mass. It suggests the angular momentum of gas on million-light-year scales may help regulate how actively galaxies form stars.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The negative vorticity–sSFR relation is only demonstrated in TNG100; the paper's own §5.3 notes the related CGM-spin trend reverses in SIMBA, so without cross-simulation replication the claimed preventative modulation remains simulation-specific.","rationale":"The strongest empirical claim is a correlation within TNG100, and for that correlation the paper does adequate fixed-halo-mass binning and an inner-gas exclusion test. The fragile step is the leap from a simulation-specific correlation to a general physical mechanism: the transfer of angular momentum from large-scale cold gas to the star-forming ISM is explicitly subgrid-dependent. The paper itself provides the key counter-evidence in §5.3, where SIMBA fails to reproduce the related CGM-spin–sSFR anti-correlation, and it attributes the difference to subgrid ISM mixing and fountain processes. That admission makes the generality of the vorticity–sSFR finding the most load-bearing uncertainty. I considered the weaker quantitative support for the 'only cold gas' uniqueness claim, but that is a secondary aspect: even if uniqueness were established within TNG100, the physical interpretation would still need cross-simulation validation. The proposed re-analysis on independent simulation codes is a direct, decisive check. Since the reader already assigned CONDITIONAL and identified the same weakest assumption, my review does not change the verdict.","tokens_in":51,"tokens_out":7582,"duration_ms":141660,"concrete_test":"Repeat the Fig. 6 analysis on public SIMBA and EAGLE (or Auriga) outputs at z=0 using identical definitions: T_gas < 2e4 K cold gas, the same 1 Mpc grid and vorticity calculation, the same halo mass bins, and the same top/bottom 30% cold-gas vorticity split. If the median sSFR offset at 10^12–10^13 M_sun is not negative and of order 0.5 dex in at least one independent code, the claim must be restricted to TNG-like subgrid physics; if it reproduces, the concern is resolved.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central physical claim, that ambient cold-gas vorticity suppresses star formation, depends entirely on TNG100's subgrid treatment of cold-gas-to-ISM angular-momentum transfer. The paper concedes in §5.3 that the closely related CGM-spin–sSFR anti-correlation is absent or reversed in SIMBA (Liu et al. 2024), and it cites Yang et al. (2024) showing that the efficiency of CGM-ISM angular-momentum transfer via fountain/mixing processes differs between Auriga and Apostle. Because the vorticity–sSFR relation is a statistical correlation in one simulation and the proposed mechanism relies on subgrid mixing and fountain physics, the 0.5 dex gap in Fig. 6 could be a TNG-specific artifact of its feedback implementation rather than a generic environmental angular-momentum effect. The paper's conclusions, which describe 'crucial evidence' and a 'unique role of cold gas', are broader than what a single simulation with acknowledged subgrid sensitivity can support.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper uses the TNG100 cosmological simulation to define a cold-gas vorticity field from gas with T_gas < 2×10^4 K on a ~1 Mpc grid at z = 0, and studies its relation to the specific star formation rate of central galaxies with 10.0 < log M_star/M_sun < 11.5. The main result is that, within fixed halo-mass bins, central galaxies in the top 30% of environmental cold-gas vorticity have lower median sSFR than those in the bottom 30%, with a median gap of ~0.5 dex at halo masses 10^12–10^13 M_sun. The paper further reports the relation among both star-forming and quenched galaxies, higher cold-gas vorticity around filament galaxies than knot galaxies at fixed halo mass, a correlation between cold-gas vorticity and satellite orbital angular momentum out to 500 kpc, and the absence of a similar modulation for total-matter or total-gas vorticity. The interpretation is that large-scale cold-gas angular momentum prevents efficient gas infall and thus regulates star-formation activeness.","tokens_in":26440,"tokens_out":5625,"duration_ms":52874,"significance":"The claimed effect is potentially interesting for environmental angular-momentum quenching, and the paper makes several good choices: it uses the public TNG100 simulation, the analysis has no fitted parameters, it bins by halo mass, and it checks robustness by excluding cold gas within r200/3 of halos. The connection to satellite orbital angular momentum and the filament/knot comparison are valuable extensions of earlier CGM-spin work. However, the headline claim rests on median comparisons without significance tests, the \"only cold gas\" conclusion is based on visual inspection of a grid-cell phase-space plot, and the paper itself acknowledges that a closely related correlation reverses in the SIMBA simulation. These issues currently make the result a promising single-simulation trend rather than a firmly established general environmental effect.","major_comments":[{"comment":"The central 0.5 dex sSFR gap between the top and bottom 30% cold-gas-vorticity environments is presented without significance tests. The error bars shown are standard errors of the mean, which do not quantify the separation of the underlying sSFR distributions or account for bin-to-bin correlations. I request bootstrap or permutation confidence intervals for the median difference, and ideally a matched-sample or partial-correlation control for overdensity and local galaxy density within each halo-mass bin. Without this, the claim in the abstract and conclusions that the negative modulation holds \"at any given halo mass\" is not statistically established.","section":"Section 4.1, Fig. 6"},{"comment":"The paper explicitly concedes that the closely related CGM-spin–sSFR anti-correlation reverses in SIMBA (Liu et al. 2024) and that the efficiency of CGM-to-ISM angular-momentum transfer depends on subgrid ISM implementation (Yang et al. 2024). Because the proposed mechanism is invoked as causal and the conclusions assert a \"unique role\" of cold gas and \"crucial evidence\", the single-simulation basis is load-bearing. Either replicate the cold-gas-vorticity–sSFR analysis in an independent simulation, or explicitly restrict the abstract and conclusions to TNG100 and reframe the environmental claim as tentative. The current wording is broader than the evidence presented.","section":"Section 5.3 and Conclusions"},{"comment":"The claim that the negative modulation is \"only significantly observed\" for cold gas rests on a qualitative inspection of color-coded grid-cell distributions, with no statistical comparison among total-matter, total-gas, and cold-gas vorticities. Moreover, the grid-cell sSFR is the ratio of summed SFR to summed stellar mass of central galaxies assigned to the same ~1 Mpc cell, so the effective sample is cells, not galaxies. Provide quantitative tests, such as median sSFR as a function of vorticity tertile for each component using galaxy-based samples, before asserting the uniqueness of the cold-gas effect.","section":"Section 5.2, Fig. 11"},{"comment":"The negative relation between cold-gas vorticity and sSFR is present only below log M_halo/M_sun ~ 13, and the lines cross above that mass, with the trend reversing. The paper attributes this to AGN feedback, but the reversal directly contradicts the unqualified abstract statement that galaxies in higher-vorticity environments are less star-forming \"at any given halo mass\". Please state the halo-mass range over which the negative relation holds, quantify the reversal, and demonstrate that it is not simply a selection effect of including AGN-dominated passive galaxies despite the stellar-mass cut.","section":"Section 4.1, Fig. 6 (upper panel)"},{"comment":"The filament-versus-knot comparison does not control for the differing halo-mass distributions of the two environmental populations; filament galaxies populate predominantly lower halo masses, while knots dominate the highest mass bins, and Fig. 8 shows only limited mass overlap. A matched-sample analysis in halo mass, overdensity, and local density is needed to support the claim that cold-gas vorticity, rather than environmental density or assembly history, drives the sSFR difference between filament and knot galaxies. As presented, the environmental-type dependence does not cleanly separate vorticity from other environmental correlates.","section":"Section 4.3, Figs. 8–9"}],"minor_comments":[{"comment":"The text uses \"~1 Mpc\" and \"~865 kpc\" interchangeably for the grid spacing; please state the exact cell size once and use consistent language thereafter.","section":"Throughout"},{"comment":"The cross-reference in Section 2.2 to \"Section 2.5\" for the mesh setup is incorrect; the mesh is described in Section 2.2, and the cosmic-web classification is in Section 2.5.","section":"Section 2.2 and Section 2.5"},{"comment":"The phrase \"We note the reader\" appears several times (e.g., Section 2.5, Section 4.1, Section 6); it should read \"We note for the reader\" or \"We remind the reader\".","section":"Throughout"},{"comment":"The phrase \"three hundreds galaxies\" should be \"three hundred galaxies\".","section":"Section 3"},{"comment":"The caption states that knot (filament) data are shaded in the left (right) panel, but the shading is not visually identified in the figure; please clarify which shaded regions correspond to which environment.","section":"Fig. 9 caption"},{"comment":"The reference list contains a LaTeX artifact \"V ogelsberger\" in several entries; these names should be rendered as \"Vogelsberger\".","section":"References"}],"recommendation":"major_revision","confidential_remarks":"This is a single-simulation correlation study with an interesting but not yet fully established central claim. The most important revisions are statistical: significance testing for the median sSFR gap, a quantitative comparison of cold-gas versus total-matter/total-gas vorticity, and a clearer separation of the vorticity effect from density and mass assembly effects. The self-citation level is high but not circular; however, the paper should more sharply distinguish which results are new relative to Wang et al. (2022) and Lu et al. (2022b)."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear colleague,\n\nWhat you should know: this is a careful TNG100 correlation study, and the central result—higher cold-gas vorticity in the ~1 Mpc environment tracks lower sSFR at fixed halo mass—is real within that simulation. The paper is honest about its biggest limitation, and that limitation is as load-bearing as it sounds.\n\nThe genuinely new piece is extending the authors' earlier CGM-spin work to a vorticity field on ~1 Mpc scales and to a general population of centrals, not just ~300 examples. The ~0.5 dex median sSFR gap between top and bottom 30% cold-gas vorticity at halo masses 10^12–10^13 Msun is a concrete, checkable number. They bin by halo mass, split by filament/knot and by star-forming/quenched, and exclude inner r200/3 gas to show the trend is not from the ISM. That is solid, reproducible analysis on public data.\n\nThe soft spots are in proportion. First, there are no significance tests on the median differences; the error bars shown are standard errors of the mean, which do not speak to whether the 0.5 dex gap is meaningful given the scatter. Second, the 'only cold gas' uniqueness claim rests on a qualitative color plot (Fig. 11); the paper never quantifies the trend slopes for the three components. Third, the causal language in the abstract and conclusions—'crucial evidence', 'unique role'—oversells what is a correlation in one simulation. The authors know this: Section 5.3 concedes the closely related CGM-spin–sSFR anti-correlation is absent or reversed in SIMBA (Liu et al. 2024), and they cite Yang et al. (2024) showing subgrid-dependent fountain mixing. That makes the claim of a universal preventative modulation speculative. The stress-test concern lands on the paper's own text.\n\nThat said, the paper is not sloppy. The caveats are present, and the analysis is transparent enough that a referee can request the missing significance tests and a quantitative component comparison without sending the authors back to square one. The citation pattern is reasonable; self-citations to prior work in this series are relevant and not circular.\n\nWho is this for? People working on environmental quenching, CGM angular momentum, and simulation subgrid comparisons. It is a within-field advance, not a breakthrough. I would not cite it as evidence of a universal mechanism, but I might cite it as a TNG-based observational target. Recommendation: it deserves a serious referee and a moderate revision.","headline":"A careful TNG-only correlation study whose causal claim exceeds its evidence, but the 0.5 dex cold-gas vorticity–sSFR gap is a real, checkable result worth a referee's time.","tokens_in":27029,"tokens_out":2742,"would_cite":false,"duration_ms":25642,"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":"At fixed halo mass, central galaxies in higher cold-gas vorticity environments form stars less actively.","keywords":["cold gas","vorticity","specific star formation rate","angular momentum environment","cosmic web","galaxy quenching","TNG100 simulation","circumgalactic medium"],"falsifier":"Run the same top-versus-bottom 30% cold-gas vorticity analysis in a different cosmological simulation whose subgrid feedback is implemented differently, for example the SIMBA simulation cited in the paper, where the related CGM-spin to sSFR trend is already reported to be reversed: if the roughly 0.5 dex sSFR gap disappears or flips sign there, the TNG100 result is code-dependent. A complementary observational check would map cold-gas velocity fields around galaxies out to roughly a megaparsec with HI surveys and measure the median sSFR difference between high- and low-vorticity environments at fixed halo mass.","tokens_in":2001,"feed_emoji":"🌀","tokens_out":2006,"duration_ms":56513,"temperature":0.7,"pith_summary":"The paper argues that the angular-momentum state of cold gas on roughly one-megaparsec scales regulates how actively a central galaxy forms stars. Using the TNG100 simulation at redshift zero, the authors find that at any given halo mass, galaxies embedded in higher cold-gas vorticity have systematically lower specific star formation rates. The cleanest quantitative claim is that for halos of $10^{12}$ to $10^{13}$ solar masses, the median sSFR of galaxies in the top 30% cold-gas vorticity is about 0.5 dex below that of galaxies in the bottom 30%. This negative modulation holds for both star-forming and quenched galaxies, in both filaments and knots, and it is only significant for the cold-gas component, not for total matter or total gas. If the claim is right, the ambient cold-gas spin field becomes a necessary ingredient for understanding why similar-mass galaxies end up with different star-formation activities.","feed_headline":"High cold-gas vorticity dims galaxy star formation by 0.5 dex","feed_subtitle":"Centrals in the top 30% of large-scale cold-gas spin form stars about three times slower than those in the bottom 30%.","key_machinery":"The central object is the cold-gas vorticity field, defined as $\\omega\\equiv\\nabla\\times\\mathbf{v}$ and evaluated from the velocity field of gas with $T_{\\rm gas}<2\\times10^4$ K on a $128^3$ mesh covering the TNG100 box (cell scale $\\sim$865 kpc). This field measures the swirl of the ambient cold gas at roughly megaparsec scales and replaces the conventional halo spin parameter as the descriptor of angular momentum in the environment. The machinery includes binning central galaxies by halo mass, splitting each bin into top and bottom 30% subsamples of vorticity or sSFR, and comparing the medians; the same grid is used to classify galaxies into knots and filaments via the Hessian of the gravitational potential, following the method of Hahn et al. (2007) and Forero-Romero et al. (2009). The vorticity field is also compared with the orbital angular momentum of neighboring galaxies within 30--500 kpc to argue for a common origin and a possible angular-momentum inheritance from the galaxy interaction environment to the cold gas.","core_discovery":"Using the TNG100 magnetohydrodynamic cosmological simulation, the authors compute the vorticity $\\omega\\equiv\\nabla\\times\\mathbf{v}$ of cold gas at $T_{\\rm gas}<2\\times10^4$ K on a grid with cell scale about 865 kpc, effectively probing the angular motion of the ambient cold gas at $\\sim$1 Mpc scales. They then compare central galaxies with stellar masses $10.0<\\log M_*/M_\\odot<11.5$ that reside in the top versus bottom 30% of the local cold-gas vorticity at fixed halo mass. The central claim is that higher cold-gas vorticity environments host galaxies with lower specific star formation rates, with the strongest signal at halo masses below $10^{13}\\,M_\\odot$; at $10^{12}$--$10^{13}\\,M_\\odot$ the median sSFR gap is about 0.5 dex. The authors interpret this as a preventative angular-momentum modulation: the swirling cold gas on large scales suppresses efficient cold-gas infall toward the galaxy center, reducing the fuel for star formation. They further show that the effect survives when the inner third of each halo is excluded from the vorticity calculation, indicating that the driver is genuinely large-scale rather than dominated by interstellar or inner-CGM gas. The same modulation is not seen for the vorticity of total matter or total gas, which the authors take as evidence for the unique role of the cold, collisional gas component.","pith_inferences":["One could test the causality of the proposed modulation using the redshift evolution: if the cold-gas vorticity genuinely suppresses gas infall, the sSFR deficit should already appear at intermediate redshift and should strengthen as the vorticity field develops; the paper only analyzes $z=0$ galaxies.","Observational velocity fields of neutral hydrogen around galaxies, such as those from future surveys that can map coherent motion out to several hundred kiloparsecs, could provide a direct empirical counterpart to the simulated cold-gas vorticity and would either corroborate or challenge the 0.5 dex gap.","The paper's exclusion of inner-halo cold gas suggests that the vorticity signal is tied to infall geometry and stream dynamics rather than to feedback-driven gas motion; varying the smoothing scale around 1 Mpc could reveal whether the anti-correlation peaks at the virial radius or at larger scales, which would discriminate between merger-driven and cosmic-web-driven origins.","If the relation is universal, then the cold-gas vorticity field should also correlate with galaxy spin orientation and with the coherence between central stellar rotation, CGM kinematics, and satellite orbits, a connection the paper leaves largely unexplored except for the comparison with neighboring-galaxy orbital angular momentum."],"forward_implications":["If the claim holds, a galaxy's star-formation activity is partly set by the rotational state of cold gas up to about a megaparsec away, so environment classifications should include the cold-gas vorticity field alongside density and cosmic-web type.","Filament galaxies should be less star-forming than knot galaxies at fixed halo mass because their cold-gas vorticity is systematically higher, which the paper presents as a natural explanation of the observed sSFR differences between these environments.","The mechanism acts as a preventative modulation: high ambient cold-gas angular momentum lowers the sSFR of star-forming galaxies and helps keep quenched galaxies quenched, operating in parallel with AGN feedback rather than replacing it.","Galaxies with extreme angular momentum, such as superthin and low-surface-brightness galaxies, are predicted to live preferentially in high-vorticity, kinematically coherent environments, a prediction that can be tested with targeted observations.","The absence of the modulation for total-matter and total-gas vorticity implies that any observational or theoretical account of galaxy quenching must track the cold gas phase specifically, not the overall gravitational or baryonic angular momentum field."],"supporting_citations":[{"why":"Establishes the earlier finding that cold circumgalactic gas and galaxy interaction environments modulate central sSFR, motivating the extension to ~1 Mpc cold-gas vorticity.","marker":"Wang et al. 2022"},{"why":"Shows a positive correlation between neighboring-galaxy orbital angular momentum and cold CGM spin, which directly motivates the vorticity definition and the inheritance picture.","marker":"Lu et al. 2022b"},{"why":"Provides the qualitative predecessor that star formation is suppressed near filament edges where gas vorticity is high.","marker":"Song et al. 2021"},{"why":"Reports that the related CGM-spin to sSFR correlation is reversed in the SIMBA simulation, used in the paper to flag the subgrid dependence of the result.","marker":"Liu et al. 2024"},{"why":"Supplies the TNG100 simulation description and the mass-dependent quenching behavior that informs the sample mass cuts.","marker":"Pillepich et al. 2018a"},{"why":"Provides the potential-Hessian cosmic-web classification that the paper adapts to separate filament and knot environments.","marker":"Hahn et al. 2007"},{"why":"Refines the threshold choice for the cosmic-web classification, yielding the volume fractions used to assign galaxies to environmental types.","marker":"Forero-Romero et al. 2009"}],"fun_headline_variants":["Cold-gas vorticity dims galaxy star formation by 0.5 dex","Swirling cold gas suppresses star formation in central galaxies","Large-scale cold gas spin linked to reduced star formation","High ambient cold-gas vorticity predicts quenched galaxies"],"cache_read_input_tokens":29184,"weakest_assumption_plain":"The load-bearing premise is that the TNG100 subgrid recipes for star formation, gas cooling, and feedback faithfully capture how large-scale cold-gas kinematics influence star-formation activity; if those recipes are inaccurate, the vorticity-to-sSFR anti-correlation could be an artifact of the simulation code rather than a general physical relation.","fun_headline_variants_meta":{"raw":{"variants":["Cold-gas vorticity dims galaxy star formation by 0.5 dex","Swirling cold gas suppresses star formation in central galaxies","Large-scale cold gas spin linked to reduced star formation","High ambient cold-gas vorticity predicts quenched galaxies"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000387,"raw_usage":{"total_tokens":2182,"prompt_tokens":1220,"completion_tokens":962,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":836,"completion_tokens_details":{"reasoning_tokens":894}},"tokens_in":836,"tokens_out":962,"duration_ms":9889,"temperature":1.0,"reasoning_tokens":894,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T12:47:51.458061+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same top-versus-bottom 30% cold-gas vorticity analysis in a different cosmological simulation whose subgrid feedback is implemented differently, for example the SIMBA simulation cited in the paper, where the related CGM-spin to sSFR trend is already reported to be reversed: if the roughly 0.5 dex sSFR gap disappears or flips sign there, the TNG100 result is code-dependent. A complementary observational check would map cold-gas velocity fields around galaxies out to roughly a megaparsec with HI surveys and measure the median sSFR difference between high- and low-vorticity environments at fixed halo mass.","supporting_citations":[{"cited_title":"Disparate Effects of Circumgalactic Medium Angular Momentum in IllustrisTNG and SIMBA","cited_arxiv_id":"2409.09379","evidence_quote":"Reports that the related CGM-spin to sSFR correlation is reversed in the SIMBA simulation, used in the paper to flag the subgrid dependence of the result."}],"review_version":1}