{"id":"b3db45c2-ca6d-4da9-9951-0d21f9fa8653","arxiv_id":"2411.19945","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"Stacked eROSITA X-ray observations show star-forming galaxies do not have brighter hot circumgalactic emission than quiescent galaxies at matched stellar or halo mass, under the adopted stellar-to-halo mass relation.","lead":"This paper stacks X-ray survey data around two types of galaxies to measure the hot gas halo (CGM) around each type. It finds star-forming galaxies do not have brighter hot gas than quiescent galaxies of the same mass, which challenges some feedback-driven quenching models.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The halo-mass part of the central claim is conditional on the Tinker (2021) bimodal SHMR; the paper's own Yang (2007) test shows the equality disappears, so only the weaker 'not brighter' statement is robust.","rationale":"The reader's weakest assumption identifies the same load-bearing concern: the equality at fixed halo mass rests on the Tinker (2021) bimodal SHMR and disappears under the Yang et al. (2007) unimodal SHMR. I agree with the reader's CONDITIONAL verdict. The direct stellar-mass-binned comparison and the 'not brighter' conclusion are supported by the tabulated luminosities and by the sSFR test in Sect. 4.3; the AGN/XRB subtraction makes the SF CGM detections low-significance, but this mainly weakens the positive detection claim, not the 'not brighter' upper limit. The load-bearing soft spot is the halo-mass equality, which the paper itself flags as conditional. The independent support (careful stacking, source masking, satellite-bias correction, comparison with two group finders) is substantial; the issue is addressed with an explicit alternative test rather than hidden, so a REJECT is not warranted. No new concern changes the reader's verdict.","tokens_in":26547,"tokens_out":7964,"duration_ms":72488,"concrete_test":"Measure the mean halo masses of the SF and QU central samples in the same stellar-mass bins using galaxy-galaxy lensing (e.g., the SDSS DR7 lensing catalogues), and recompute the LX,CGM-versus-M500c relation using these lensing-based masses instead of the Tinker (2021) group-finder masses. If the SF and QU relations separate at fixed lensing mass (as they do with the Yang et al. 2007 SHMR), the halo-mass equality is an artifact of the adopted SHMR; if they overlap, the conclusion is robust.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's headline conclusion contains two components: (1) at fixed stellar mass, star-forming (SF) galaxies are not brighter than quiescent (QU) galaxies, and (2) at fixed halo mass they host equally bright hot CGM, interpreted as 'halo mass is the determining factor' (Sect. 3.2 and 4.1). Component (2) is not a direct measurement because halo masses are not observed; they are assigned by the Tinker (2021) group finder, whose masses are calibrated to reproduce the bimodal stellar-to-halo mass relation (SHMR) of Mandelbaum et al. (2016). The paper demonstrates in Sect. 4.1 and Fig. 5 that repeating the same stacking with the Yang et al. (2007) unimodal SHMR yields different LX,CGM-M500c relations, with SF galaxies fainter than QU. The authors state this explicitly: 'We conclude that the consistent LX,CGM-M500c scaling relations ... are conditional upon the bimodal SHMR' (Sect. 4.1). Thus the positive claim that galaxies in same-mass halos host equally bright CGM, and the interpretation that halo mass rather than star-formation state sets CGM luminosity, is a projection of the LX-M* relation through one particular SHMR. The weaker statement, that SF are not brighter than QU, survives under both SHMRs, but the equality claim does not.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper stacks four eROSITA all-sky survey (eRASS:4) maps around volume-limited samples of ~32,000 central star-forming and ~53,000 central quiescent SDSS DR7 galaxies, plus the corresponding halo-mass-selected samples, at zspec < 0.2. It measures mean 0.5–2 keV X-ray surface brightness profiles out to R500c, subtracts detected point sources, unresolved AGN, X-ray binaries, and satellite contributions, and integrates the residual as LX,CGM. It reports extended hot CGM emission around quiescent galaxies with log M* > 10.5 and star-forming galaxies with log M* > 11.0, a bifurcation in the LX,CGM–M* scaling relation above log M* ~ 11.0, and consistent LX,CGM–M500c relations for star-forming and quiescent galaxies when using the Tinker (2021) group finder's bimodal SHMR. The paper shows that this halo-mass equality is not reproduced when halo masses are assigned with the Yang et al. (2007) group finder. It compares the measured relations to EAGLE, TNG100, and SIMBA and discusses discrepancies with the earlier eFEDS stacking studies. The concluding claim is that, whether selected in stellar mass or halo mass, star-forming galaxies do not host brighter stacked X-ray emission from the hot CGM than their quiescent counterparts at the same mass.","tokens_in":26780,"tokens_out":7975,"duration_ms":67893,"significance":"If the main result holds, it suggests that hot CGM X-ray luminosity is not enhanced by ongoing star formation at fixed stellar or halo mass and that halo mass, rather than current star formation state, is the primary determinant of CGM heating — a useful constraint for quenching models and their feedback implementations. The paper's strengths include large central-galaxy samples, careful masking and modeling of unresolved AGN/XRB emission, an explicit test of the SHMR dependence, and a transparent statement that the halo-mass equality is conditional on the adopted bimodal SHMR. The robust part of the conclusion (star-forming galaxies are not brighter) is well supported, but the stronger equality claim is only established under one particular SHMR, and the star-forming CGM detections are marginal in several bins.","major_comments":[{"comment":"The abstract and the fourth bullet of Section 5 state that galaxies in the same mass dark matter halos host equally bright hot CGM and that halo mass is the determining factor; this is only true for the Tinker (2021) bimodal SHMR. The paper's own test with the Yang et al. (2007) group finder yields LX,CGM-M500c relations in which star-forming galaxies are fainter than quiescent galaxies, and the text concludes that the consistent relations are 'conditional upon the bimodal SHMR'. The abstract and conclusions should be revised to present the equality as an SHMR-dependent result and to separate it from the robust statement that star-forming galaxies are not brighter.","section":"Section 4.1, Fig. 5"},{"comment":"The star-forming LX,CGM values are low-significance detections, e.g., 2.3±1.5×10^40 erg/s in the log M*=11.0-11.25 bin and 4.0±2.4×10^40 erg/s in the 11.25-11.5 bin, corresponding to roughly 1.5-2 sigma. The claim that extended X-ray emission from the hot CGM is 'detected' around star-forming galaxies with log M*>11.0 is not supported at high confidence by the integrated luminosities. The later statement that star-forming and quiescent galaxies host 'equally bright' CGM in halo mass bins should be reframed as consistency within large uncertainties or as an upper limit for the star-forming population.","section":"Table 3, Sections 3.1 and 3.2"},{"comment":"The simulation comparison mixes apertures: simulated LX,CGM is measured within (0.15-1)R500c, while the observed LX,CGM is integrated within the full R500c. The paper acknowledges the 'face value' nature of the comparison, but it does not quantify the resulting bias. A matched-aperture measurement or an explicit aperture correction is needed before the degree of agreement with EAGLE, TNG100, and SIMBA can be assessed.","section":"Section 4.2, Fig. 7"},{"comment":"For star-forming galaxies, the modeled XRB plus unresolved AGN emission is comparable to or larger than the residual LX,CGM (e.g., 2.6±1.1 versus 2.3±1.5 ×10^40 erg/s in the 11.0-11.25 stellar mass bin). The paper notes that proper beta-model fits cannot be applied to star-forming galaxies because of this, but the systematic uncertainty of the Aird et al. (2017) XRB model and of the BPT-based AGN estimate is not propagated into LX,CGM. A quantitative assessment of these systematics is required for the detection claim.","section":"Section 3.1, Table 3, Appendix A"}],"minor_comments":[{"comment":"The total sample sizes quoted in the text (32,190 CENSF and 53,032 CENQU) differ from the sums of the corresponding Table 1 bins (31,243 and 52,130, respectively); please verify and make the numbers consistent.","section":"Table 1, Section 2.1"},{"comment":"The summation symbol appears to be missing in the rendered equations; the equations should be written with explicit sums over events and radial bins.","section":"Equations (1)-(2)"},{"comment":"The sequences '0.8, 2.3, 4.0×10^40' and '1.1, 6.2, 30×10^40' should be written with the same scientific notation for each value for clarity.","section":"Abstract"},{"comment":"The statement that 'a satellite fraction of about 40-50% can explain the bright LX' is imprecise because Fig. 9 labels the quantities as lower limits ('fsat > 40%' and 'fsat > 50%'); please clarify whether these are lower limits.","section":"Section 4.4.1, Fig. 9"},{"comment":"The captions contain a typo ('bottem'), and they should specify whether the shown SX,CGM profiles already have the unresolved AGN and XRB models subtracted when comparing with the beta-model fits.","section":"Figures 2 and 3"},{"comment":"The simulated uncertainties are the 16-84% scatter of individual simulated galaxies, while the observed uncertainties are errors on the mean; this difference should be stated in the figure captions as well as in the text.","section":"Section 4.2, Fig. 7"}],"recommendation":"major_revision","confidential_remarks":"This is a solid stacking analysis with a clear methodology and an unusually honest treatment of the SHMR dependence. The main problem is that the abstract and conclusions overstate the halo-mass equality claim, which the paper itself demonstrates is conditional on the Tinker (2021) bimodal SHMR, while the star-forming CGM detections are only marginal in several bins. I would encourage a revision that reframes the abstract and Section 5 to separate the SHMR-dependent equality from the robust 'not brighter' claim, adds quantitative significance statements, and corrects the simulation comparison aperture. With those changes the paper should be publishable in A&A."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: this is a careful, useful stacking paper, and the stress-test note is right in substance but not fatal. The measurement people should remember is the robust one: at fixed stellar mass, star-forming centrals are not X-ray brighter than quiescent centrals; above log M* ~ 11 they are actually fainter. The separate claim that galaxies in same-mass halos host equally bright CGM is a projection of the LX-M* relation through the Tinker (2021) bimodal SHMR. The paper itself demonstrates this with the Yang (2007) test and says the consistent M500c relations are conditional upon the bimodal SHMR. So the abstract's final sentence is the load-bearing claim, and it holds.\n\nWhat is genuinely new: this is the first all-sky eRASS:4 stacking of the hot CGM split by star-forming and quiescent central galaxies. The sample is large, approximately volume-limited, and restricted to centrals with misclassification checked. The analysis masks detected point sources, models XRB, unresolved AGN, and satellite contamination, and provides both LX-M* and LX-M500c relations plus the SHMR-sensitivity demonstration. That is real, citable progress over Comparat et al. (2022) and Chadayammuri et al. (2022), and the comparison to EAGLE, TNG100, and SIMBA is a useful addition.\n\nWhere the soft spots are: the star-forming CGM detections are weak. Several LX,CGM values are only 1.5-2.4 sigma, and the authors state that XRB plus unresolved AGN contribute about 50-100% of the SF X-ray flux in the low-mass bins. They also say SF profiles cannot be beta-model fitted. So the extended-CGM detection around star-forming galaxies is a residual after substantial subtraction, not a clean detection. The halo-mass equality result is conditional on the adopted SHMR; if a unimodal SHMR is true, that equality disappears. The paper is transparent about this, which earns credit, but the interpretation that \"halo mass is the determining factor\" should be presented as a projection, not a direct measurement. The simulation comparison is done at face value without a dedicated mock; the authors acknowledge the different uncertainty definitions, and that is a minor caveat, not a fatal one.\n\nWho gets value: anyone working on CGM X-ray scaling relations, galaxy quenching, or feedback implementation in simulations. The tables alone are worth having. I would send this to a serious referee; a good one should push on the SHMR-conditional interpretation and ask the authors to state more precisely where the SF detection is robust versus residual-dominated. The central conclusion is solid enough to deserve referee time.","headline":"Solid eRASS:4 stacking paper whose robust result—star-forming centrals are not X-ray brighter at fixed mass—survives; the stronger halo-mass equality is explicitly conditional on the bimodal SHMR, and the paper is honest about that.","tokens_in":27498,"tokens_out":2069,"would_cite":true,"duration_ms":22333,"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":"Stacking X-ray light around tens of thousands of SDSS central galaxies, this paper argues that star-forming galaxies do not host brighter hot circumgalactic medium than quiescent galaxies of equal stellar or halo mass.","keywords":["circumgalactic medium","hot gas","X-ray stacking","star-forming galaxies","quiescent galaxies","stellar-to-halo mass relation","eROSITA","galaxy quenching"],"falsifier":"Re-run the stacking using halo masses derived from a weak-lensing-calibrated stellar-to-halo mass relation; if the $L_{X,\\rm CGM}$–$M_{500c}$ relations for star-forming and quiescent galaxies separate, the paper's equal-brightness halo-mass claim is refuted.","tokens_in":26264,"feed_emoji":"🌌","tokens_out":7856,"duration_ms":59911,"temperature":0.7,"pith_summary":"This paper asks whether the hot gas halo around a galaxy knows whether the galaxy is forming stars. Using stacked X-ray images from the first four eROSITA all-sky surveys around roughly 85,000 central galaxies from SDSS DR7, the authors measure soft X-ray emission from the circumgalactic medium (CGM) separately for star-forming and quiescent galaxies, selected in both stellar mass and halo mass. They find that at fixed stellar mass above $\\log(M_*/\\mathrm{M}_\\odot) \\simeq 11.0$, quiescent galaxies host brighter hot CGM, but at fixed halo mass above $\\log(M_{200m}/\\mathrm{M}_\\odot) \\simeq 12.5$ the two populations look the same. Their headline conclusion is that star-forming galaxies never host brighter hot CGM than quiescent galaxies of the same mass, and that halo mass, rather than the current star-formation state, appears to set how much X-ray light the CGM emits. This matters because feedback from star formation and active galactic nuclei is often invoked to heat and expel CGM gas and shut down star formation; the result constrains how strong such feedback can be.","feed_headline":"Star-forming galaxies do not glow brighter in hot CGM X-rays","feed_subtitle":"Halo mass, not ongoing star formation, sets the hot circumgalactic medium's X-ray luminosity in stacked eROSITA data.","key_machinery":"The machine is the stacked X-ray surface brightness profile: events from the first four eROSITA all-sky surveys are co-added in radial bins around SDSS DR7 central galaxies, with detected point sources masked and unresolved active galactic nuclei plus X-ray binaries modeled and subtracted, so the remaining soft X-ray emission is attributed to the hot CGM. The profiles are fit with a $\\beta$-model, and $L_{X,\\rm CGM}$ is the integral within $R_{500c}$. The comparison that carries the argument is between two selections of the same sample: bins in stellar mass $M_*$, where quiescent systems above $\\log(M_*/\\mathrm{M}_\\odot) = 11.0$ are brighter, and bins in halo mass $M_{200m}$ from the Tinker (2021) group finder, where star-forming and quiescent profiles are consistent; the bimodal stellar-to-halo mass relation is what converts one selection into the other, and the paper shows that switching to the unimodal Yang et al. (2007) SHMR destroys the halo-mass equality.","core_discovery":"The central claim is that the hot CGM X-ray luminosity of central galaxies is set by halo mass, not by whether the galaxy is star-forming or quiescent. Concretely, the stacked 0.5–2 keV emission within $R_{500c}$ gives $L_{X,\\rm CGM} \\approx 8\\times 10^{39}$, $2.3\\times 10^{40}$, and $4.0\\times 10^{40}$ erg/s for star-forming galaxies with median stellar masses $\\log(M_*/\\mathrm{M}_\\odot) = 10.7$, $11.1$, and $11.3$, and $1.1\\times 10^{40}$, $6.2\\times 10^{40}$, and $3.0\\times 10^{41}$ erg/s for quiescent galaxies with median stellar masses $10.8$, $11.1$, and $11.4$; quiescent systems are brighter above $\\log(M_*/\\mathrm{M}_\\odot) > 11.0$. When the same galaxies are binned by halo mass using the Tinker (2021) group finder, star-forming and quiescent galaxies with $\\log(M_{200m}/\\mathrm{M}_\\odot) > 12.5$ show consistent surface brightness profiles and consistent $L_{X,\\rm CGM}$–$M_{500c}$ relations, implying that galaxies in similar dark matter halos host equally bright hot CGM. The paper states that this halo-mass conclusion is conditional on the bimodal stellar-to-halo mass relation, because repeating the halo-mass selection with the unimodal Yang et al. (2007) SHMR produces different $L_{X,\\rm CGM}$–$M_{500c}$ relations; the SHMR-independent statement that survives is the title conclusion that star-forming galaxies are not brighter.","pith_inferences":["If the equal-brightness result holds, it suggests quenching is not accompanied by an unusually hot or luminous CGM; the gas reservoir looks the same whether star formation is ongoing or shut off, which points toward halo mass or assembly history as the quenching switch.","The strong SHMR dependence implies that the cleanest test will come from weak-lensing-calibrated halo masses; the same stacking repeated with those masses would either confirm or dissolve the halo-mass conclusion.","The paper's identification of satellite-boost bias and star contamination as the source of earlier conflicting results suggests that other stacked CGM measurements built from less clean central samples may need to be revisited.","Measuring CGM temperature or metallicity from stacked spectra, rather than luminosity alone, would test whether the gas around star-forming and quiescent galaxies is in the same physical state even when its X-ray brightness matches."],"forward_implications":["Quiescent galaxies with $\\log(M_*/\\mathrm{M}_\\odot) > 11.0$ appear brighter in hot CGM X-ray emission than star-forming galaxies of the same stellar mass, while below that mass the two are comparable.","Binned by halo mass with the Tinker (2021) group finder, star-forming and quiescent central galaxies above $\\log(M_{200m}/\\mathrm{M}_\\odot) \\simeq 12.5$ show consistent X-ray surface brightness and luminosity, so halo mass, not star-formation state, is the primary driver of CGM heating.","If the bimodal stellar-to-halo mass relation is replaced by a unimodal one, the equal-brightness halo-mass result disappears and star-forming galaxies appear fainter than quiescent ones, so future SHMR measurements will either support or overturn the halo-mass interpretation.","Comparisons with three cosmological hydrodynamical simulations show disagreement in some mass bins, so the measured relations provide a constraint on how much energy feedback can deposit in or remove from the hot CGM."],"supporting_citations":[{"why":"Defines the stacking method, background estimation, and satellite-boost corrections that this paper applies to star-forming and quiescent split samples.","marker":"Zhang et al. (2024a)"},{"why":"Supplies the group finder halo masses $M_{200m}$ and the bimodal stellar-to-halo mass relation used for halo-selected samples.","marker":"Tinker (2021)"},{"why":"Provides an alternative unimodal stellar-to-halo mass relation used to test whether the halo-mass result survives.","marker":"Yang et al. (2007)"},{"why":"Provides the lensing-based bimodal SHMR that motivates the halo-mass interpretation and calibrates the Tinker (2021) catalog.","marker":"Mandelbaum et al. (2016)"},{"why":"Supplies the X-ray binary luminosity model used to subtract stellar X-ray contamination from the stacked emission.","marker":"Aird et al. (2017)"},{"why":"Provides the SFR and 4000 Å break measurements used to split galaxies into star-forming and quiescent samples.","marker":"Brinchmann et al. (2004)"},{"why":"Provides the stellar masses for the SDSS DR7 galaxy samples.","marker":"Chen et al. (2012)"},{"why":"Earlier eROSITA stacking result whose brighter quiescent emission is re-examined and attributed to satellite boost bias.","marker":"Comparat et al. (2022)"},{"why":"Earlier stacking result with different conclusions, compared here to test the role of sample size, central selection, and star contamination.","marker":"Chadayammuri et al. (2022)"}],"fun_headline_variants":["Halo mass sets hot CGM brightness, not star formation","Star-forming galaxies don't shine brighter in hot CGM","eROSITA: Halo mass, not galaxy type, drives hot CGM glow","Hot CGM X-ray glow matches halo mass, not star formation"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The conclusion that star-forming and quiescent galaxies in matched halos shine equally bright assumes that the halo masses assigned by the Tinker (2021) group finder, with its two-branch stellar-to-halo mass relation, are the true halo masses.","fun_headline_variants_meta":{"raw":{"variants":["Halo mass sets hot CGM brightness, not star formation","Star-forming galaxies don't shine brighter in hot CGM","eROSITA: Halo mass, not galaxy type, drives hot CGM glow","Hot CGM X-ray glow matches halo mass, not star formation"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000368,"raw_usage":{"total_tokens":2206,"prompt_tokens":1405,"completion_tokens":801,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":1021,"completion_tokens_details":{"reasoning_tokens":725}},"tokens_in":1021,"tokens_out":801,"duration_ms":6990,"temperature":1.0,"reasoning_tokens":725,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T05:39:20.737605+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-run the stacking using halo masses derived from a weak-lensing-calibrated stellar-to-halo mass relation; if the $L_{X,\\rm CGM}$–$M_{500c}$ relations for star-forming and quiescent galaxies separate, the paper's equal-brightness halo-mass claim is refuted.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the group finder halo masses $M_{200m}$ and the bimodal stellar-to-halo mass relation used for halo-selected samples."},{"cited_title":"2016, MNRAS, 457, 3200","cited_arxiv_id":null,"evidence_quote":"Provides the lensing-based bimodal SHMR that motivates the halo-mass interpretation and calibrates the Tinker (2021) catalog."}],"review_version":1}