{"id":"192e461a-9826-4f6a-b8f0-7670a86eef47","arxiv_id":"2606.28874","paper_version":2,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":6.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Stellar surface density independently modulates MgII outflow equivalent width in massive star-forming galaxies at 0.35<z<1.0 observed by DESI.","lead":"This paper reports that MgII cool-gas outflow absorption strength in DESI star-forming galaxies rises with stellar surface density even in samples matched on stellar mass and SFR. A smart generalist might read it to understand how galaxy compactness influences feedback and gas outflows beyond total mass or star formation rate.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.3","headline":"Matching on M* and Balmer SFR proxy may leave residual correlations with dust attenuation or morphology that affect MgII EW independently of Σ*.","rationale":"The identified concern directly matches the reader's weakest assumption. Full-text details on matching implementation would be required to close it; absent those, the isolation of Σ* remains unverified, supporting a CONDITIONAL rather than UNVERDICTED or ACCEPT verdict.","tokens_in":1741,"tokens_out":345,"duration_ms":23556,"concrete_test":"In the matched samples, compare distributions of g-r color, Sérsic index (from DESI imaging), and any available metallicity indicator across the three Σ* tertiles using KS tests; if any property shows p<0.01 difference, recompute the EW trend after additional matching on that property and check whether the 0.37-0.61 Å rise persists.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim requires that Σ* remains the sole independent driver after matching. The abstract states AGN-clean samples are matched in stellar mass and (stricter) in both M* and Balmer-line SFR proxy, with EW rising 0.37-0.61 Å across Σ* tertiles. However, compactness (smaller Re at fixed M*) correlates with higher dust content, higher Sérsic index, and possibly different gas-phase conditions; if the matching procedure (bin widths, tolerances, or multivariate balance) does not also equalize these, the monotonic EW trend could trace those residuals rather than Σ* itself. The paper's own note that velocity changes only weakly makes covering-fraction or optical-depth effects plausible confounders.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript analyzes DESI DR1 stacked spectra of massive star-forming galaxies at 0.35<z<1.0 to show that MgII cool-gas outflow equivalent width increases monotonically with stellar surface density Σ*=M*/(2πRe²) after AGN cleaning and matching on stellar mass (and more strictly on both M* and a Balmer-line SFR proxy). EW rises 0.37-0.61 Å across Σ* tertiles in every redshift bin while outflow velocity changes only weakly, implying that galaxy compactness modulates cool-gas outflow properties independently of total stellar mass or SFR.","tokens_in":1863,"tokens_out":494,"duration_ms":22850,"significance":"If the matching isolates Σ* without residual biases, the result supplies a clear empirical demonstration that structural compactness is an additional coordinate for cool-gas outflow strength in massive star-forming galaxies, based on a large spectroscopic dataset with redshift binning. This strengthens the case for incorporating surface density into feedback models beyond the usual M*–SFR scaling.","major_comments":[{"comment":"The sample-matching procedure (described in the methods section on AGN-clean samples) must demonstrate that residuals in dust attenuation, Sérsic index, or gas-phase metallicity are balanced across Σ* tertiles; otherwise the monotonic EW trend could arise from these correlated properties rather than Σ* itself, undermining the claim that Σ* is an independent driver.","section":"Sample construction and matching"},{"comment":"Given the paper's note that absolute outflow velocity changes only weakly, the EW increase is plausibly driven by covering fraction or optical-depth variations rather than changes in outflow strength or velocity distribution; this distinction should be quantified (e.g., via line-profile modeling) to support the interpretation of modulated outflow strength.","section":"Results on velocity and EW trends"}],"minor_comments":[{"comment":"Clarify the exact definition and measurement of the Balmer-line SFR proxy used for the stricter matching, including any aperture or dust corrections applied.","section":"Methods"},{"comment":"Add error bars or bootstrap uncertainties to the reported EW differences (0.37-0.61 Å) and state the number of galaxies per tertile and redshift bin.","section":"Results"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their constructive comments, which help clarify the robustness of our results. We address each major comment below and indicate where revisions will be made.","responses":[{"response":"We agree that explicit checks on these residuals are needed to support the independence claim. In the revised manuscript we will add supplementary material (tables and/or violin plots) showing the distributions and medians of dust attenuation (A_V from SED fits or Balmer decrement), Sérsic index (from DESI imaging or external catalogs), and gas-phase metallicity (where emission-line measurements are available) across the Σ* tertiles in both the M*-matched and M*+SFR-proxy-matched samples. Preliminary internal checks indicate these quantities are well balanced after matching, but we will quantify any small residuals and discuss their possible influence on the EW trend.","revision_made":"yes","referee_comment":"[Sample construction and matching] The sample-matching procedure (described in the methods section on AGN-clean samples) must demonstrate that residuals in dust attenuation, Sérsic index, or gas-phase metallicity are balanced across Σ* tertiles; otherwise the monotonic EW trend could arise from these correlated properties rather than Σ* itself, undermining the claim that Σ* is an independent driver."},{"response":"We already note in the manuscript that the weak velocity change implies the EW trend is driven by covering fraction or optical-depth variations rather than bulk velocity shifts. Full line-profile modeling of stacked spectra would require detailed assumptions about geometry, ionization, and multiple components that are not feasible within the scope of this empirical study. We will expand the discussion to more explicitly frame the result in terms of increased effective covering fraction or column density in compact galaxies, while retaining the current interpretation that Σ* modulates cool-gas outflow properties independently of M* and SFR.","revision_made":"partial","referee_comment":"[Results on velocity and EW trends] Given the paper's note that absolute outflow velocity changes only weakly, the EW increase is plausibly driven by covering fraction or optical-depth variations rather than changes in outflow strength or velocity distribution; this distinction should be quantified (e.g., via line-profile modeling) to support the interpretation of modulated outflow strength."}],"tokens_in":1409,"tokens_out":475,"duration_ms":30473,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The central result is that MgII equivalent width increases monotonically with stellar surface density in mass-matched and mass-plus-SFR-matched samples of DESI star-forming galaxies at 0.35<z<1. The rise is 0.37-0.61 Å across tertiles while outflow velocity shifts only weakly. This is presented as evidence that galaxy structure affects cool-gas outflow absorption beyond total mass or star-formation rate.\n\nThe work uses a large survey dataset and applies AGN cleaning plus sample matching, which is a direct way to test the claim. The consistency across redshift bins is a plus, and the result is framed as purely observational without overclaiming mechanisms.\n\nThe main soft spot is the matching itself. Compactness at fixed mass and SFR often correlates with higher dust attenuation, higher Sérsic index, and altered gas conditions. If the procedure does not also balance those properties, the EW trend could trace residuals rather than surface density alone. The weak velocity change makes covering fraction or optical depth effects plausible confounders, and the abstract does not detail bin widths, tolerances, or post-match checks on other observables.\n\nThis paper is for researchers working on empirical constraints for galaxy feedback and outflow modeling. A reader focused on absorption-line studies or structural parameters in galaxy evolution would find the empirical coordinate useful to consider.\n\nIt is worth sending for peer review so the matching details and potential systematics can be examined properly.","headline":"DESI stacked spectra show MgII EW rising with stellar surface density after matching on mass and Balmer SFR, but the isolation may not be complete.","tokens_in":2316,"tokens_out":361,"would_cite":false,"duration_ms":22678,"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":"Stellar surface density increases MgII cool-gas outflow absorption in star-forming galaxies beyond effects of total mass or star-formation rate.","keywords":["stellar surface density","MgII absorption","galaxy outflows","cool gas","star-forming galaxies","galaxy structure"],"falsifier":"A new stacked or individual-galaxy sample, matched identically on stellar mass and Balmer SFR proxy, in which MgII equivalent width shows no systematic rise across stellar surface density tertiles.","tokens_in":2627,"feed_emoji":"🌌","tokens_out":567,"duration_ms":23944,"temperature":0.7,"pith_summary":"The paper tests whether the tightness with which stars are packed in a galaxy affects the strength of its cool-gas outflows, using stacked spectra of massive star-forming galaxies. It finds that the equivalent width of MgII absorption, a tracer of outflowing cool gas, rises steadily with stellar surface density even after samples are matched on stellar mass and on a Balmer-line star-formation rate proxy. This structural dependence appears in every redshift bin examined and points to changes in the velocity distribution or covering fraction of the absorbing gas. A sympathetic reader would care because the result implies that outflow coupling is not governed solely by the total fuel or total stars but also by how the stellar mass is spatially arranged.","feed_headline":"Stellar surface density boosts MgII outflow strength","feed_subtitle":"Equivalent width rises 0.37-0.61 Å with compactness even after mass and SFR matching in DESI star-forming galaxies","key_machinery":"Stellar surface density Σ★ = M★ / (2π R_e²), used as an independent empirical coordinate that modulates the strength of down-the-barrel MgII cool-gas absorption after mass and SFR matching.","core_discovery":"In AGN-clean samples of massive star-forming galaxies at 0.35 < z < 1.0 drawn from DESI Data Release 1, the MgII outflow equivalent width rises monotonically with stellar surface density Σ★ = M★ / (2π R_e²) in every redshift bin. The increase from lowest to highest Σ★ tertile is 0.37–0.61 Å when samples are matched on stellar mass alone and persists in a stricter sample also matched on a Balmer-line SFR proxy. The absolute outflow velocity changes only weakly with Σ★, while the structural trend is interpreted as evidence that galaxy compactness alters the absorbing velocity distribution or the effective covering fraction of cool outflowing gas.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Stellar density modulates MgII outflow in DESI galaxies","MgII outflow EW rises with stellar surface density","Compactness ties to MgII absorption in star forming galaxies","DESI shows density modulates MgII cool gas absorption"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"That matching samples on stellar mass and Balmer-line SFR proxy plus AGN cleaning isolates stellar surface density as the independent variable without residual biases from other galaxy properties or measurement systematics.","fun_headline_variants_meta":{"raw":{"variants":["Stellar density modulates MgII outflow in DESI galaxies","MgII outflow EW rises with stellar surface density","Compactness ties to MgII absorption in star forming galaxies","DESI shows density modulates MgII cool gas absorption"]},"model":"grok-4.3","cost_usd":0.005829,"raw_usage":{"total_tokens":2818,"prompt_tokens":758,"num_sources_used":0,"completion_tokens":62,"cost_in_usd_ticks":58287000,"prompt_tokens_details":{"text_tokens":758,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1998,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":758,"tokens_out":62,"duration_ms":22017,"temperature":1.0,"reasoning_tokens":1998,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-01T06:30:08.470345+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A new stacked or individual-galaxy sample, matched identically on stellar mass and Balmer SFR proxy, in which MgII equivalent width shows no systematic rise across stellar surface density tertiles.","supporting_citations":[],"review_version":2}