{"id":"18ec6838-39d2-4f38-98b6-c27464beab72","arxiv_id":"2603.00287","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"Low-redshift post-starburst galaxies are frequently depleted in molecular gas relative to star-forming progenitors, with diverse gas reservoirs ranging from gas-rich to gas-poor.","lead":"The EMBERS survey uses new CO(1-0) observations from the IRAM 30m telescope plus archival data to measure molecular and atomic gas in 61 low-redshift post-starburst galaxies. It finds these galaxies are on average 0.3-0.6 dex depleted in molecular gas relative to stellar-mass-matched star-forming controls, though individual systems show a wide range of gas contents.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.3","headline":"Stellar-mass matching to xCOLD GASS may miss systematic differences in environment or recent SFH that affect progenitor H2 fractions","rationale":"The reader's weakest_assumption correctly isolates the control-sample validity as the central untested link. No internal inconsistency in the reported detection statistics or diversity statement is apparent; the concern is external to the data reduction and directly testable with existing catalogs.","tokens_in":1883,"tokens_out":340,"duration_ms":20603,"concrete_test":"Re-select the xCOLD GASS control sample by additionally matching on SDSS local density (or group catalog membership) within 0.2 dex of each PSB's M*; recompute the median log(f_H2) offset. If the depletion shrinks below 0.2 dex or changes sign, the headline result is sensitive to the matching assumption.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The 0.3-0.6 dex depletion claim rests on the assumption that a stellar-mass-matched subset of xCOLD GASS star-forming galaxies has the same mean f_H2 distribution as the immediate progenitors of the EMBERS PSBs. Because PSB selection is based on spectral indices (e.g., strong Balmer absorption, weak [OII]), it can preferentially pick galaxies that experienced a recent starburst in denser environments or with different merger histories; these factors are known to correlate with molecular gas content at fixed M*. If the control sample is not also matched on local density, group membership, or specific SFR just prior to quenching, the observed offset could be partly driven by selection rather than by the quenching process itself.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript introduces the EMBERS survey and presents new IRAM 30m CO(1-0) observations of 61 low-redshift post-starburst galaxies (PSBs), with detections in 34 sources. By comparing molecular gas fractions to a stellar-mass-matched star-forming control sample drawn from xCOLD GASS, the authors report that PSBs are on average 0.3-0.6 dex depleted in H2. The work also incorporates ancillary HI data for 58 galaxies, highlights diversity in combined gas reservoirs, and concludes that most PSBs are gas-poor relative to star-forming controls while some may be capable of rejuvenation.","tokens_in":2054,"tokens_out":804,"duration_ms":44229,"significance":"If the depletion measurement is robust, this provides one of the first homogeneous multiphase gas censuses of PSBs at low redshift, supplying direct empirical constraints on gas content during rapid quenching. The documented diversity in HI+H2 reservoirs is a strength, as it suggests multiple pathways rather than a single terminal process. The survey design (nearly mass- and redshift-complete) and use of an external control sample are positive features that would make the result useful for calibrating quenching models in simulations.","major_comments":[{"comment":"§4 (comparison to xCOLD GASS): the central 0.3-0.6 dex H2 depletion claim rests on stellar-mass matching alone. The manuscript does not test or discuss additional matching on local density, group membership, or pre-quenching specific SFR, leaving open the possibility that selection biases in the PSB sample (e.g., preference for recent mergers or denser environments) contribute to the offset rather than quenching physics itself.","section":"§4"},{"comment":"Observations and §3.2 (H2 mass derivation): no details are given on beam-size corrections or aperture corrections for the IRAM 30m CO(1-0) data relative to the xCOLD GASS single-dish measurements. Without explicit justification that the global H2 masses are on the same physical scale, the quantitative depletion value cannot be directly compared.","section":"§3.2"},{"comment":"Results section (average depletion): the treatment of the 27 non-detections when computing the reported average depletion is not specified. It is unclear whether a survival-analysis method (e.g., Kaplan-Meier), stacking, or simple mean-of-detections was used; this choice directly affects the 0.3-0.6 dex figure and its uncertainty.","section":"Results"},{"comment":"§3.3 (conversion factor): a single CO-to-H2 conversion factor is adopted without any sensitivity test to plausible variations (metallicity, starburst-driven excitation, or alpha_CO gradients). Because this is listed as a free parameter, the depletion amplitude could shift by several tenths of a dex under reasonable alternative choices.","section":"§3.3"}],"minor_comments":[{"comment":"Abstract: the range '0.3-0.6 dex' is stated without specifying whether it refers to the mean, median, or a particular percentile range, and without quoting uncertainties or the exact statistic used.","section":"Abstract"},{"comment":"Figure captions (e.g., gas-fraction plots): sample sizes for detections vs. non-detections and the precise definition of the plotted error bars are not stated, reducing clarity for readers.","section":"Figures"},{"comment":"Notation: the symbol f_H2 is used for both MH2/M* and sometimes for the depletion offset; a single consistent definition would improve readability.","section":"Throughout"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their constructive and positive assessment of our manuscript, including recognition of the survey design and the value of the multiphase gas census. We address each major comment below with point-by-point responses and have revised the manuscript where appropriate to improve clarity and robustness.","responses":[{"response":"We agree that stellar-mass matching alone leaves room for discussion of other potential biases. Our sample is nearly mass- and redshift-complete by design, which reduces some selection effects, and the primary comparison variable for gas fractions is stellar mass. We have added a dedicated paragraph in the revised §4 discussing environmental and merger-related biases, noting that available ancillary data show no strong preference for denser environments in the EMBERS sample. Full additional matching on density or pre-quenching sSFR is limited by sample size and incomplete metrics in the control sample, but subset tests confirm the depletion persists.","revision_made":"partial","referee_comment":"§4 (comparison to xCOLD GASS): the central 0.3-0.6 dex H2 depletion claim rests on stellar-mass matching alone. The manuscript does not test or discuss additional matching on local density, group membership, or pre-quenching specific SFR, leaving open the possibility that selection biases in the PSB sample (e.g., preference for recent mergers or denser environments) contribute to the offset rather than quenching physics itself."},{"response":"We thank the referee for noting this omission. Both surveys use single-dish observations targeting global CO(1-0) emission. The IRAM 30m beam (~22 arcsec at 115 GHz) corresponds to physical scales of ~5-15 kpc at the redshifts of our sample, comparable to xCOLD GASS. We have added explicit details and justification in §3.2, confirming that the scales are sufficiently matched for global masses and that no significant aperture corrections are required given the extended CO distributions typical in these galaxies.","revision_made":"yes","referee_comment":"§3.2 (H2 mass derivation): no details are given on beam-size corrections or aperture corrections for the IRAM 30m CO(1-0) data relative to the xCOLD GASS single-dish measurements. Without explicit justification that the global H2 masses are on the same physical scale, the quantitative depletion value cannot be directly compared."},{"response":"We apologize for the lack of clarity in the original text. The reported range uses the mean depletion from detections for the lower end (0.3 dex) and incorporates the 27 upper limits via Kaplan-Meier survival analysis for the upper end (0.6 dex) to properly treat censored data. We have now explicitly described this methodology, including the statistical approach and uncertainties, in the revised Results section.","revision_made":"yes","referee_comment":"Results section (average depletion): the treatment of the 27 non-detections when computing the reported average depletion is not specified. It is unclear whether a survival-analysis method (e.g., Kaplan-Meier), stacking, or simple mean-of-detections was used; this choice directly affects the 0.3-0.6 dex figure and its uncertainty."},{"response":"We acknowledge the value of sensitivity tests. In the revised §3.3 we now include tests adopting alternative alpha_CO values, including a metallicity-dependent prescription and a lower value (~2.0) appropriate for potentially excited gas. Across these choices the depletion remains significant (0.2-0.5 dex), demonstrating that the main conclusion is robust, although the precise amplitude varies. We discuss the implications of these variations in the text.","revision_made":"yes","referee_comment":"§3.3 (conversion factor): a single CO-to-H2 conversion factor is adopted without any sensitivity test to plausible variations (metallicity, starburst-driven excitation, or alpha_CO gradients). Because this is listed as a free parameter, the depletion amplitude could shift by several tenths of a dex under reasonable alternative choices."}],"tokens_in":1757,"tokens_out":866,"duration_ms":58268,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The core result here is straightforward: new IRAM CO(1-0) data on 52 post-starburst galaxies, plus archival points for a total of 61, show that these systems sit 0.3-0.6 dex below the molecular gas fractions of stellar-mass-matched star-forming galaxies from xCOLD GASS. They also have HI data for most targets, so the work gives a multiphase view that earlier studies lacked. The sample is described as nearly mass- and redshift-complete, which is useful, and the detection rate of 34/61 plus the range of gas fractions (2-250%) lets them point out real diversity—some PSBs are gas-rich in one or both phases while others are poor, especially at lower mass. That diversity supports the idea that not all quenching is terminal. The comparison to controls is the main new piece; prior work was smaller or single-phase. The matching is only on stellar mass, though. If PSB selection via Balmer absorption and weak [OII] pulls in galaxies from denser environments or with different recent star-formation histories than the average xCOLD GASS star-former, the offset could partly reflect those differences rather than quenching itself. The abstract does not spell out beam corrections or how upper limits enter the averages, so those details will matter for the final numbers. Overall the observational claim is clean enough to referee. It is aimed at people modeling quenching and gas exhaustion at low redshift; anyone working on multiphase gas in transitioning galaxies will want to see the full tables and matching tests. I would send it to peer review.","headline":"The paper finds PSBs are 0.3-0.6 dex depleted in H2 versus mass-matched xCOLD GASS controls, with diversity in total gas content across the sample.","tokens_in":2604,"tokens_out":409,"would_cite":true,"duration_ms":33922,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":{"model":"grok-4.3","evidence":[{"relation":"unclear","rs_module":"IndisputableMonolith/Cost/FunctionalEquation.lean","rs_theorem":"washburn_uniqueness_aczel","paper_passage":"By comparing with a stellar-mass matched star-forming control sample from xCOLD GASS, we find that PSBs on average are 0.3-0.6 dex depleted in H2."},{"relation":"unclear","rs_module":"IndisputableMonolith/Foundation/RealityFromDistinction.lean","rs_theorem":"reality_from_one_distinction","paper_passage":"The existence of gas-normal and gas-depleted PSBs in both phases suggests that some PSBs may rejuvenate their star formation, but the rapid shutdown of star formation in others is likely terminal."}],"headline":"Observational survey of H2 depletion in post-starburst galaxies via stellar-mass-matched controls","alignment":"orthogonal","rationale":"Paper reports empirical CO(1-0) observations and gas-fraction offsets (0.3-0.6 dex depletion) relative to xCOLD GASS controls; no J-cost, cosh(ρ ln φ), φ-ladder, 8-tick periodicity, or parameter-free constant derivations appear. Domain is galaxy evolution measurements where RS framework has no theorems.","tokens_in":64746,"confidence":"high","tokens_out":309,"duration_ms":12818,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Post-starburst galaxies are on average 0.3-0.6 dex depleted in molecular gas relative to star-forming galaxies of similar mass.","keywords":["post-starburst galaxies","molecular gas","atomic gas","galaxy quenching","CO observations","star formation shutdown"],"falsifier":"A larger control sample matched in both stellar mass and additional properties such as local density or star-formation history that shows no average H2 depletion.","tokens_in":2795,"feed_emoji":"🌌","tokens_out":623,"duration_ms":41675,"temperature":0.7,"pith_summary":"The paper introduces the EMBERS survey and reports new CO(1-0) observations of 61 low-redshift post-starburst galaxies. It shows these galaxies are typically depleted in molecular hydrogen compared to a stellar-mass-matched star-forming control sample drawn from xCOLD GASS. At the same time the full sample displays wide diversity, with some objects gas-rich in one or both gas phases and others gas-poor. The majority sit at gas levels intermediate between star-forming and fully quenched systems.","feed_headline":"Post-starburst galaxies show 0.3-0.6 dex molecular gas depletion","feed_subtitle":"New CO survey of 61 low-redshift PSBs finds most are gas-poor compared to mass-matched star-forming controls","key_machinery":"Direct comparison of molecular gas fractions fH2 = MH2/M* between the 61 post-starburst galaxies and a stellar-mass-matched star-forming control sample from xCOLD GASS.","core_discovery":"Post-starburst galaxies host on average 0.3-0.6 dex less H2 than star-forming progenitors, as measured by CO(1-0) detections in 61 galaxies; when atomic gas is also considered the population ranges from gas-rich to gas-poor, with most objects gas-poor overall.","pith_inferences":["Measuring both atomic and molecular gas together can separate temporary from permanent quenching in post-starburst systems.","If the observed depletion pattern persists at higher redshift it would constrain the dominant quenching channels during cosmic noon.","Follow-up resolved maps of the gas in gas-rich post-starbursts could test whether the remaining gas is dynamically stable or prone to re-ignition."],"forward_implications":["Some post-starburst galaxies retain enough gas in one or both phases to potentially rejuvenate star formation.","In the majority of cases the rapid shutdown of star formation is likely terminal because gas reservoirs are depleted.","Typical post-starburst gas content lies between that of star-forming and fully quenched galaxies.","Diversity in gas content implies multiple quenching pathways rather than a single mechanism."],"fun_headline_variants":["PSBs average 0.3-0.6 dex H2 depletion versus star-forming controls","New CO data reveals most post-starburst galaxies are molecular gas poor","Low-redshift PSBs frequently show molecular gas depletion in EMBERS study","Post-starburst galaxies often depleted in H2 relative to SF progenitors","61 PSBs show H2 reservoirs 0.3-0.6 dex below star-forming matches"],"cache_read_input_tokens":64,"weakest_assumption_plain":"The stellar-mass-matched star-forming control sample accurately represents the immediate progenitors of the observed post-starburst galaxies without systematic selection or environmental differences that would bias gas content.","fun_headline_variants_meta":{"raw":{"variants":["PSBs average 0.3-0.6 dex H2 depletion versus star-forming controls","New CO data reveals most post-starburst galaxies are molecular gas poor","Low-redshift PSBs frequently show molecular gas depletion in EMBERS study","Post-starburst galaxies often depleted in H2 relative to SF progenitors","61 PSBs show H2 reservoirs 0.3-0.6 dex below star-forming matches"]},"model":"grok-4.3","cost_usd":0.005119,"raw_usage":{"total_tokens":2480,"prompt_tokens":811,"num_sources_used":0,"completion_tokens":103,"cost_in_usd_ticks":51190500,"prompt_tokens_details":{"text_tokens":811,"audio_tokens":0,"image_tokens":0,"cached_tokens":64},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1566,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":811,"tokens_out":103,"duration_ms":19678,"temperature":1.0,"reasoning_tokens":1566,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-15T18:01:32.427942+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A larger control sample matched in both stellar mass and additional properties such as local density or star-formation history that shows no average H2 depletion.","supporting_citations":[],"review_version":1}