{"id":"7ae7d3b6-75d5-4bea-8daa-366d46c7fc1f","arxiv_id":"2502.05329","paper_version":3,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Resolved supernova heating and stellar mass loss in 3D simulations naturally produce cool-core-like and non-cool-core-like interstellar media whose properties are set by the confining circumgalactic pressure.","lead":"Simulations of the central few kiloparsecs of massive elliptical galaxies show that Type Ia supernovae and mass lost from old stars set the density and temperature of the hot gas, with the surrounding circumgalactic medium controlling which of two states the gas settles into. The results connect galaxy-scale gas to black hole feeding and may explain why some massive galaxies have cool cores and others do not.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The fixed 10 kpc density/temperature boundary imposes the CGM pressure whose influence is the central claim; the long uniform-heating run suggests a live CGM would cool inward, so the two solution classes may depend on an unchanging boundary.","rationale":"The reader's weakest assumption is squarely on target, and I agree with it. The paper's central physical picture is plausible and well supported by the parameter survey and by the resolved-SN treatment; there is no internal inconsistency in the numerics that I can identify. The concern is that the outer boundary condition doubles as the mechanism: because §2 shows the inner solution is a subsonic pressure-confined extension of the CGM, holding the CGM state fixed at 10 kpc essentially preselects the family of quasi-steady solutions that the simulations then find. The long uniform-heating run already hints that the outer CGM wants to cool, and the absence of a discrete-SN version at large radius leaves open whether the quasi-steady states persist when the boundary is allowed to respond. This does not warrant rejection—the paper is transparent about the boundary condition and about the role of AGN at large radii—but it does justify keeping the verdict CONDITIONAL, pending a live-CGM test. The reader and I therefore agree, and no verdict change is needed beyond the reader's original conditional assessment.","tokens_in":24803,"tokens_out":5270,"duration_ms":56926,"concrete_test":"Run the 'fid' model with discrete SNIa in an enlarged domain with outer boundary at 30 kpc, initializing the CGM with the observed entropy profile and allowing it to cool and flow, and evolve to ≥1 Gyr; repeat once with the original fixed 10 kpc boundary to isolate boundary effects. If the inner 3 kpc density/entropy profiles stay within ~20% of the fiducial run until a cooling front reaches r≈3 kpc, the pressure-confinement mechanism is robust; if they evolve toward the cooling-flow branch within a few hundred Myr, the two solution classes are at least partly artifacts of the rigid boundary.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 3.6 fixes density and temperature at the 10 kpc outer boundary to their initial values for the whole run. This is not a neutral buffer: the analytical argument in §2, especially eq. (3), predicts the subsonic breeze velocity scales inversely with the CGM density, so fixing ρ_CGM and T_CGM at 10 kpc imposes the very quantity whose influence is the paper's headline result. The simulations therefore show that a maintained CGM pressure produces a corresponding inner ISM state; they do not show that the real CGM would maintain that pressure when the galaxy's AGB mass loss and SNIa energy cross the boundary. The paper's own 'outer-uni20-long' run (§6) shows cooling at r≳10 kpc beginning to collapse within 1.2 Gyr, but because it uses uniform heating we do not know whether discrete SNIa would delay this or whether the cooling front would propagate inward and erase the quasi-steady state. The 'quasi-steady-state' classification also relies largely on 100 Myr runs: the fiducial run is in the intermediate regime theat<tcool<tAGB, and 'double-SN' has not converged by 100 Myr. A live or time-dependent CGM boundary could move the system between the two classes on timescales shorter than the run duration.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents 3D hydrodynamic simulations of the central few kiloparsecs of massive elliptical galaxies, with a gravitational potential set by stars, dark matter, and a central black hole, and with gas physics including radiative cooling, smooth AGB mass/energy injection, and Type Ia supernovae injected as resolved discrete events. The fiducial model is initialized to match the observed density and entropy profiles of NGC 1399. The authors identify two classes of quasi-steady solutions over 100 Myr: when SNIa heating exceeds cooling, a subsonic 'breeze' expels most AGB ejecta, with the inner ISM profile set by the confining CGM pressure (giving cool-core-like or non-cool-core-like states); when cooling dominates, a cooling flow develops with a much larger black hole accretion rate. A parameter study varies the initial entropy, pressure, SNIa rate, and SNIa injection method, showing that resolved SNIa produce different density/entropy profiles and accretion rates than uniform or clustered injection schemes.","tokens_in":25016,"tokens_out":6401,"duration_ms":68215,"significance":"If the central claim holds, this is a valuable numerical demonstration of the Voit et al. (2020) picture in which the galaxy-scale ISM is a pressure-confined, stellar-heated system whose thermodynamic state is inherited from the surrounding CGM even though its mass is predominantly AGB ejecta. The resolved treatment of individual SNIa remnants (fade radius resolved by at least 4 cells) is a genuine improvement over smooth-heating models, and the systematic parameter survey provides a useful map of the solution branches and their dependence on CGM pressure and SNIa rate. The most robust quantitative results are the convergence of different initial entropy profiles at fixed pressure (Fig. 5) and the monotonic variation of the black hole accretion rate with CGM pressure and SNIa rate. The paper is also unusually candid about its limitations, including the late-time cooling at large radii and the absence of AGN feedback.","major_comments":[{"comment":"The outer boundary at 10 kpc fixes density and temperature to their initial values for the entire run. This is not a neutral buffer: the analytic argument in §2, especially Eq. (3), predicts that the outflow velocity scales inversely with the CGM density, so fixing ρ_CGM and T_CGM at the boundary imposes the pressure-confinement effect that is the paper's headline result. The simulations therefore demonstrate that the inner ISM adjusts to a maintained CGM pressure, but they do not test whether a realistic, time-dependent CGM would maintain that pressure while receiving AGB ejecta and SNIa energy from the galaxy. The one long, large-domain run ('outer-uni20-long', §6) uses uniform heating and shows cooling at r ≳ 10 kpc beginning within 1.2 Gyr; because the heating is not resolved, this run cannot exclude the possibility that discrete SNIa delay or alter the cooling. I recommend either adding a resolved-SN run with a larger outer boundary or implementing a simple live/responding CGM boundary to show that the inheritance of CGM properties is not purely built into the boundary condition.","section":"§3.6 and Eq. (3)"},{"comment":"The fiducial run's agreement with NGC 1399 is partly built in. The entropy normalization S0, slope α_S, and density n0 are chosen to match the Werner et al. (2012) profiles, and the SNIa rate is set (footnote 3) to a value that makes net stellar heating exceed radiative cooling, thereby selecting the heating-dominated branch. Consequently, the abstract's statement that the simulations 'reproduce its observed density and entropy profiles well' describes a tuned consistency check rather than an independent prediction. The more compelling results are the convergence of different S0 runs at fixed pressure and the pressure dependence of the final profiles (Figs. 5–7). I ask the authors to rephrase the reproduction claim as calibration and to place the primary evidentiary weight on the parameter study.","section":"§3.1 and footnote 3"},{"comment":"The two-class classification rests mainly on runs of 100 Myr, which is comparable to or shorter than the cooling time at the outer boundary. The paper itself states that the 'double-SN' run has not reached a statistical steady state by 100 Myr, and the 'fid' run lies in the intermediate regime theat < tcool < tAGB (Fig. 6). Given that the only 1.2 Gyr run shows a late-time transition to cooling inflow at r ≳ 10 kpc (§6), it is not established that the inner quasi-steady states persist over multiple boundary cooling times. A convergence diagnostic, such as the time evolution of the radial mass flux and entropy profiles over several tAGB, or an explicit estimate of the steady-state timescale based on tcool at the boundary, would substantiate the 'quasi-steady-state' terminology.","section":"§4.4 and Table 1"}],"minor_comments":[{"comment":"The sentence following the reference 'Fabian 2012' is missing a space ('...Fabian 2012)he supermassive black holes'); the reference list also contains a LaTeX encoding artifact in 'B¨ ohringer'.","section":"§1"},{"comment":"The long-duration run is labeled 'outer-uni20-long' in Table 1 but is referred to as 'uni20' in the Figure 10 caption and in the text; please unify the naming.","section":"§6 and Figure 10"},{"comment":"The abstract says 'with black hole accretion at small radii', but the accretion rate is first quantified only in §4.2 via Fig. 7; a brief pointer in §3.6 describing how ˙M is measured from the sink would improve readability.","section":"§3.2"},{"comment":"The introduction cites the near-balance of SNIa heating and cooling as motivation, while footnote 3 sets the fiducial rate so that heating exceeds cooling; these statements are compatible, but an explicit reconciliation (e.g., the balance is approximate and the paper deliberately biases toward the heating-dominated branch) would avoid apparent tension.","section":"§1 and §3.2"},{"comment":"The software list includes 'LLaMA (Grattafiori et al. 2024)' alongside numerical and plotting libraries; if a language model was used for writing or analysis, the journal's AI-use disclosure policy may require a separate statement in the acknowledgments.","section":"§9 / Software section"}],"recommendation":"major_revision","confidential_remarks":"The paper is a serious numerical study well within the journal's scope, and I think the core idea is defensible. My main concern is that the central 'ISM inherits CGM properties' claim is contingent on the fixed outer boundary, and the quasi-steady-state classification rests on runs whose duration is comparable to the boundary cooling time. I have recommended major revision to allow the authors to address these points with additional diagnostics or a live-boundary test. Separately, the appearance of LLaMA in the software list may warrant an editorial check on AI-use disclosure."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Bottom line: this is the first 3D simulation I know of that resolves individual Type Ia remnants in a realistic massive elliptical with AGB mass loss and cooling, and it shows the injection method changes the answer qualitatively. The strongest section is §5: uniform and clustered SNIa injection both give density, entropy and black hole accretion rates that disagree with the resolved runs, so the resolution is not a technical nicety. That result will get cited. The parameter survey in §4 is also genuinely useful: runs with different initial entropy but the same pressure at 2 kpc converge to the same inner profiles, which is real evidence that the system loses memory of its initial condition and is set by the ambient pressure plus stellar mass return. The paper also gives Voit et al. (2020) proper credit for the qualitative two-solution picture.\n\nThe soft spots are real but not fatal. First, the outer boundary at 10 kpc holds density and temperature fixed for the whole run, which imposes the CGM pressure whose influence is the headline claim. The paper's own long run with uniform heating (outer-uni20-long) shows cooling at r > 10 kpc within 1.2 Gyr, so a live CGM might not maintain that pressure, and we do not know whether discrete SNIa would delay it. That said, the fixed-pressure versus fixed-temperature runs at 2 kpc, well inside the boundary, show the same pressure dependence, and the analytic argument in §2 gives a physical reason for it. So I read the boundary condition as a quantitative limitation on the realism of the runs, not a hole in the mechanism.\n\nSecond, the match to NGC 1399 is partly circular: the initial entropy normalization, slope, and density are taken from Werner et al. (2012), and footnote 3 says the SNIa rate was raised so that heating exceeds cooling. The 'reproduction' is therefore a consistency check, not an independent prediction. The qualitative two-branch picture does not depend on that tuning.\n\nThird, 'steady state' is doing some work. Most runs are 100 Myr, double-SN has not converged, and the fiducial run sits in the intermediate regime with theat < tcool < tAGB. The long run suggests a cooling flow would eventually develop at large radii without AGN. The authors say this in §7, so the framing is honest, but the two classes are better described as states sustained by a maintained boundary pressure.\n\nWho is this for? Anyone working on the ISM/CGM of ellipticals, stellar feedback, or AGN feeding. It deserves a serious referee. I would accept it, and I'd ask for either a discrete-SN run with a live or time-dependent outer boundary, or a clear statement that the quantitative claims apply to a maintained-pressure system. I'd also soften the 'reproduces NGC 1399' language to 'consistent with, given inputs drawn from the same data.'","headline":"Resolved-SNIa simulations that make a solid qualitative case for CGM pressure setting the ISM state in massive ellipticals, but the quantitative match to NGC 1399 is partly built in and the fixed outer boundary deserves a caveat.","tokens_in":25644,"tokens_out":4313,"would_cite":true,"duration_ms":40343,"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":"In massive elliptical galaxies, Type Ia supernovae and AGB stellar mass loss—not AGN feedback—can set the thermodynamic state of the inner few kiloparsecs, making it a pressure-confined extension of the surrounding circumgalactic medium.","keywords":["early-type galaxies","interstellar medium","Type Ia supernovae","AGB mass loss","galactic winds","cooling flows","circumgalactic medium","hydrodynamic simulations"],"falsifier":"Run the same NGC 1399 setup with a live, evolving CGM, for example by allowing the outer boundary to respond to cooling, inflows, or AGN-driven shocks, and compare the inner density and entropy profiles and black-hole accretion rate at 100 Myr. If the ISM state ceases to track the CGM pressure or the two steady-state solutions disappear, the central claim is falsified; alternatively, a systematic X-ray survey showing no correlation between inner ISM entropy and CGM entropy across massive ellipticals would also contradict the prediction.","tokens_in":2114,"feed_emoji":"💥","tokens_out":2478,"duration_ms":67728,"temperature":0.7,"pith_summary":"The paper argues that the hot gas filling the central few kiloparsecs of massive elliptical galaxies is regulated by stellar sources: mass returned by AGB stars and heating by Type Ia supernova remnants. In 3D hydrodynamic simulations of NGC 1399-like galaxies with black-hole feedback deliberately absent, two quasi-steady states emerge. If supernova heating beats cooling, the supernovae drive a slow subsonic outflow of AGB ejecta that is pressure-confined by the circumgalactic medium, so the interstellar medium's density and entropy track the CGM. If cooling wins instead, a cooling flow develops with much larger black-hole accretion. The fiducial run reproduces the observed density and entropy profiles of NGC 1399, suggesting that the inner ISM and black-hole accretion rate can be regulated by CGM pressure communicated through stellar-heated gas, even when AGN jets act at larger radii.","feed_headline":"SNIa-driven breeze sets core gas state of massive galaxies","feed_subtitle":"Resolved supernova remnants make galaxy ISM inherit CGM pressure, matching NGC 1399's X-ray profiles.","key_machinery":"The load-bearing mechanism is the combination of AGB stellar mass return, discrete SNIa injection resolved down to the remnant fade radius r_fade ~ 17.3 pc (n/0.3 $cm^{-3}$)^(-1/3) (T/1.5e7 K)^(-1/3), and a fixed pressure boundary at 10 kpc representing the inner CGM. Individual supernova remnants reach pressure equilibrium with the hot ISM and then rise buoyantly, which transports energy to larger radii; the resulting large-scale flow is a highly subsonic breeze whose velocity adjusts to the bounding CGM pressure. This pressure confinement is what allows the ISM to become a hydrostatic extension of the CGM even though the mass source interior to the galaxy (AGB winds) is completely different from the mass source exterior to it.","core_discovery":"The central claim is that the interstellar medium on galaxy scales is an AGB/SNIa-regulated system whose state is set primarily by the confining pressure of the surrounding CGM, not by the detailed initial conditions of the galaxy core. With each Type Ia supernova resolved down to its fade radius of roughly 20 pc, the remnants reach pressure equilibrium and rise buoyantly, redistributing energy away from their injection sites. For a fixed galaxy, two quasi-steady solutions emerge: a subsonic 'breeze' carrying AGB ejecta outward when the supernova heating time is shorter than the cooling time, with the ISM inheriting the CGM's entropy and density, or a cooling inflow when the cooling time is shorter than both the heating time and the AGB mass-injection time. The simulations reproduce the observed profiles of NGC 1399, and the black-hole accretion rate varies by orders of magnitude across the two branches, being largest in the cooling-flow solution and smallest in the low-density, high-entropy non-cool-core-like solution.","pith_inferences":["If the pressure-confinement logic holds, the inner ISM entropy and density of massive ellipticals should correlate tightly with the entropy and density of the inner CGM across a galaxy sample; a strong observed correlation would support CGM-driven regulation even without directly detecting the subsonic breeze.","The model implies that black-hole accretion in quiescent ellipticals may be set largely by CGM pressure communicated through the hydrostatic, stellar-heated ISM, rather than by local Bondi physics alone.","The fixed outer boundary is an important simplification; coupling the simulation to a live, evolving CGM would test whether time-dependent pressure changes, such as those from AGN outbursts or CGM cooling, are communicated inward on the roughly 100 Myr timescale relevant to the ISM.","Because uniform SNIa heating overpredicts core entropy, large cosmological simulations that treat supernova feedback as a smooth, density-proportional heating term may systematically underestimate black-hole accretion in massive ellipticals."],"forward_implications":["For the same central galaxy, a low-pressure, high-entropy CGM produces a low-density, high-entropy ISM, while a high-pressure, cool-core-like CGM produces a dense, low-entropy ISM; the system preserves cool-core versus non-cool-core character.","Black-hole accretion increases with CGM pressure, being roughly 30 times larger in the cooling-flow branch than in the cool-core-like solution and another factor of about 10 larger still relative to the highest-entropy non-cool-core-like solution.","Resolving individual SNIa remnants is essential: uniform heating overheats the core and flattens the entropy profile, while clustered, more energetic supernovae underheat the inner kiloparsec and can trigger a cooling flow, so approximate treatments give incorrect ISM profiles and incorrect black-hole accretion rates.","In the fiducial solution, AGB ejecta enrich the inner kiloparsec to a mass fraction near unity, which can explain the near-solar metallicities in massive ellipticals, with SNIa ejecta peaking around 1 kpc.","At radii beyond about 10 kpc, stellar heating may be insufficient to balance cooling, and the long-duration simulation shows the onset of a cooling inflow there, implying AGN feedback is still needed at large radii while SNIa act on kiloparsec scales."],"supporting_citations":[{"why":"Proposed that CGM pressure confines the SNIa-regulated ISM and connects CGM properties to galaxy scales; this paper tests and largely supports that picture with resolved simulations.","marker":"Voit et al. (2020)"},{"why":"Provides the observed density and entropy profiles of nearby massive ellipticals, including the NGC 1399 constraints used to initialize and validate the fiducial model.","marker":"Werner et al. (2012)"},{"why":"Supplies the Type Ia supernova rate per unit stellar mass used in the mass and energy injection scheme.","marker":"Maoz & Graur (2017)"},{"why":"Supplies the AGB stellar mass-loss rate that sets the mass return from the old stellar population.","marker":"Conroy et al. (2009)"},{"why":"Provides the two-class wind solution (supersonic wind versus subsonic breeze) that frames the dependence of the SNIa-driven outflow on the confining pressure.","marker":"Cantó et al. (2000)"},{"why":"Justifies the method of injecting SNIa energy at the remnant fade radius and shows that individual remnants reach pressure equilibrium before significant radiative losses.","marker":"Li et al. (2020a)"},{"why":"Shows that supernova remnants rise buoyantly after pressure equilibrium, which is the mechanism by which resolved SNIa deposit energy at larger radii.","marker":"Mohapatra & Quataert (2024)"},{"why":"Supplies the temperature-dependent cooling function used in the radiative cooling term.","marker":"Schure et al. (2009)"},{"why":"Provides the NGC 1399 X-ray luminosity within 22 kpc used to show that SNIa heating roughly balances the galaxy's net X-ray emission.","marker":"Su et al. (2017)"}],"fun_headline_variants":["Resolved supernovae reveal CGM sets galaxy ISM state","AGB winds and SNIa shape galaxy cores, not black holes","CGM pressure dictates galaxy ISM: breeze or cooling flow","Simulations match NGC 1399: SNIa breeze or cooling inflow","Resolving SNIa remaps galaxy ISM evolution"],"cache_read_input_tokens":27648,"weakest_assumption_plain":"The outer boundary at 10 kpc is held at fixed density and temperature for the entire simulation, effectively acting as a rigid, unchanging CGM pressure reservoir; if the real CGM cools, is shock-heated by AGN jets, or develops inflows, the pressure-confinement loop that makes the ISM inherit CGM properties may be weaker or time dependent.","fun_headline_variants_meta":{"raw":{"variants":["Resolved supernovae reveal CGM sets galaxy ISM state","AGB winds and SNIa shape galaxy cores, not black holes","CGM pressure dictates galaxy ISM: breeze or cooling flow","Simulations match NGC 1399: SNIa breeze or cooling inflow","Resolving SNIa remaps galaxy ISM evolution"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000201,"raw_usage":{"total_tokens":1454,"prompt_tokens":1093,"completion_tokens":361,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":709,"completion_tokens_details":{"reasoning_tokens":273}},"tokens_in":709,"tokens_out":361,"duration_ms":4217,"temperature":1.0,"reasoning_tokens":273,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-08T19:45:28.573475+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same NGC 1399 setup with a live, evolving CGM, for example by allowing the outer boundary to respond to cooling, inflows, or AGN-driven shocks, and compare the inner density and entropy profiles and black-hole accretion rate at 100 Myr. If the ISM state ceases to track the CGM pressure or the two steady-state solutions disappear, the central claim is falsified; alternatively, a systematic X-ray survey showing no correlation between inner ISM entropy and CGM entropy across massive ellipticals would also contradict the prediction.","supporting_citations":[{"cited_title":"M., Bryan, G","cited_arxiv_id":null,"evidence_quote":"Proposed that CGM pressure confines the SNIa-regulated ISM and connects CGM properties to galaxy scales; this paper tests and largely supports that picture with resolved simulations."}],"review_version":1}