arxiv: 2603.15235 · v2 · submitted 2026-03-16 · 🌌 astro-ph.GA

Recognition: 2 theorem links

· Lean Theorem

Towards physically more comprehensive AGN modelling in cosmological simulations: A MACER-based modification of IllustrisTNG

Bocheng Zhu , Volker Springel , Feng Yuan

Authors on Pith no claims yet

Pith reviewed 2026-05-15 10:20 UTC · model grok-4.3

classification 🌌 astro-ph.GA

keywords AGN feedbackblack hole accretioncosmological simulationsgalaxy evolutionIllustrisTNGself-regulationMACER model

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The pith

Substituting MACER feedback prescriptions into IllustrisTNG leaves cosmic star formation and galaxy mass functions largely unchanged because black hole accretion self-adjusts to release similar total feedback energy.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper replaces the AGN feedback energy output rules in the IllustrisTNG cosmological simulation with prescriptions taken from the more detailed MACER model while leaving the black hole accretion rate estimator untouched. Tests on both idealized elliptical galaxies and full cosmological volumes show that the modified model produces higher star formation and black hole accretion rates in ellipticals together with improved gas density profiles. In the cosmological runs the overall evolution of star formation rate density, the z=0 stellar mass function, and the high-mass end of the stellar-to-black-hole mass relation remain similar to the original TNG results. The modified version reproduces low-mass black holes in low-mass galaxies more accurately and applies milder quenching to massive galaxies, although it removes the clear color bimodality. The close agreement in global outcomes demonstrates that the accretion rate automatically compensates for changes in feedback efficiency so that the total energy injected by AGN stays comparable.

Core claim

Adopting MACER prescriptions for feedback output at high and low accretion rates inside the TNG framework yields a higher star formation rate and black hole accretion rate in elliptical galaxies, a gas density profile closer to observations, and better reproduction of low-mass black holes, while the cosmic star formation rate density evolution, z=0 stellar mass function, and high-mass M_star-M_BH relation stay similar to the original TNG run; this similarity arises because the accretion rate adjusts to deliver comparable total AGN feedback energy despite the altered feedback energetics.

What carries the argument

MACER feedback output prescriptions for high- and low-accretion regimes substituted directly into the unchanged TNG accretion rate estimator.

If this is right

Total AGN feedback energy released over cosmic time remains comparable between the two models because accretion rates self-adjust.
Gas density profiles inside elliptical galaxies move closer to observed values.
Low-mass black holes inside low-mass galaxies are reproduced more accurately.
Quenching of star formation in massive galaxies becomes milder while color bimodality disappears.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Refinements to small-scale AGN feedback energetics alone may leave large-scale cosmological predictions stable unless the accretion rate calculation is also revised.
The self-regulation mechanism could be tested by applying the same substitution to other subgrid AGN models beyond TNG.
Extending the approach to higher-resolution zoom simulations would reveal whether the improved low-mass black hole population persists at finer scales.

Load-bearing premise

MACER feedback prescriptions can be inserted into the TNG accretion rate estimator without any recalibration of the accretion model or addition of new free parameters.

What would settle it

A measurement showing that the time-integrated AGN feedback energy released by the MACER-modified run differs substantially from the original TNG run across the same volume and resolution.

read the original abstract

Active galactic nuclei (AGN) feedback plays a significant role in many aspects of galaxy formation and evolution and has become a key ingredient in cosmological simulations. However, the subgrid models of AGN feedback in cosmological simulations such as IllustrisTNG (hereafter TNG) often overlook recent progress in the small-scale modelling of black hole (BH) accretion and AGN physics. In this study, we improve on this by incorporating central aspects of the MACER model, a framework that treats AGN physics in greater detail, into the TNG feedback implementation. Specifically, we adopt MACER-prescriptions for feedback output for high and low accretion rates in a new model while the estimation of the accretion rate remains unchanged. We test this updated scenario both for idealized elliptical galaxies and for a cosmological box. Compared to the original TNG model, the MACER-based simulation leads to a higher star formation rate (SFR) and BH accretion rate in ellipticals, yielding a gas density profile in better agreement with observations. In the cosmological simulations, the time evolution of the SFR density, galaxy stellar mass function at $z=0$, and $M_{\star}-M_{\rm BH}$ relation at $M_{\star}>10^{10.5}\,{\rm M_{\odot}}$ are similar in both models. The MACER model better reproduces low-mass BHs in low-mass galaxies, and yields milder quenching in massive galaxies, although this is accompanied by the absence of a pronounced colour bimodality. Still, the similarity of the outcomes underlines the self-regulated nature of BH feedback: for different feedback energetics, the accretion rate tends to adjust such that a similar total AGN feedback energy is released.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Grafting MACER feedback output rules into TNG while leaving the accretion estimator untouched produces similar global galaxy statistics, which the authors read as self-regulation, but the test does not directly demonstrate compensatory adjustment.

read the letter

The main point is that grafting MACER feedback output rules onto the TNG accretion estimator produces galaxy populations that match the original TNG run in most global statistics. This is presented as evidence that black hole feedback self-regulates. The work does a few things right. They run both idealized elliptical galaxy simulations and a cosmological volume. In the isolated ellipticals the new model yields higher star formation and black hole accretion rates, which improves the match to observed gas density profiles. In the cosmological box the star formation rate density evolution, the z=0 stellar mass function, and the high-mass end of the stellar mass-black hole mass relation stay close to TNG. They also report better reproduction of low-mass black holes in low-mass galaxies and milder quenching at the high-mass end, even if the color bimodality is lost. The soft spot is the self-regulation interpretation. Because the accretion rate formula is left exactly as in TNG, the similarity in outcomes could simply reflect that shared module rather than an active adjustment in accretion that compensates for the different feedback energetics. The abstract does not include direct comparisons of total injected feedback energy or time series of accretion rates, so the claim rests on the final similarity alone. That makes the result interesting but not conclusive on the mechanism. This paper is aimed at researchers who build or tune AGN subgrid models in large-volume simulations. It offers a concrete example of how to import more detailed small-scale prescriptions without destroying the calibrated large-scale behavior. The tests are straightforward and the differences are clearly documented. I would send it to peer review. The modification is well-motivated and the numerical experiments are solid enough to merit referee scrutiny, even if the discussion of self-regulation could be strengthened with additional diagnostics.

Referee Report

3 major / 2 minor

Summary. The manuscript introduces a MACER-based modification to the AGN feedback model in IllustrisTNG, adopting MACER prescriptions for feedback output at high and low accretion rates while retaining the original TNG accretion rate estimator. Tests on idealized elliptical galaxies show higher SFR and BH accretion rates leading to improved gas density profiles. In cosmological simulations, the SFR density evolution, z=0 stellar mass function, and high-mass M_star-M_BH relation remain similar, with improvements in low-mass BHs and milder quenching, though without color bimodality. The authors conclude that the outcome similarity demonstrates self-regulation in BH feedback, where accretion adjusts to yield comparable total feedback energy despite different energetics.

Significance. If the self-regulation interpretation holds, this work is significant for advancing AGN subgrid modeling in cosmological simulations by integrating more detailed small-scale physics from MACER. It suggests that global galaxy properties are robust to changes in feedback output formulas when the accretion estimator is fixed, which could simplify future refinements and improve predictions for low-mass BH populations.

major comments (3)

Abstract: The central claim that similarity in outcomes 'underlines the self-regulated nature of BH feedback' and that 'the accretion rate tends to adjust such that a similar total AGN feedback energy is released' lacks direct supporting evidence, as no comparison of cumulative AGN feedback energy injected or of BH accretion rate time series between the original TNG and MACER-based runs is presented.
Cosmological simulations section: The unchanged TNG accretion rate estimator, which was originally calibrated to match observations, may drive the observed similarity in large-scale properties independently of the feedback output change, raising the possibility that the result partly inherits the original calibration rather than demonstrating compensatory self-regulation.
Idealized elliptical galaxies section: While qualitative improvements in gas density profiles are reported, the abstract provides no quantitative error bars or metrics (e.g., chi-squared fits or profile residuals) to assess the degree of improvement over TNG.

minor comments (2)

Abstract: The statement that the MACER model 'yields milder quenching in massive galaxies' should be accompanied by a specific quantitative measure, such as the fraction of quenched galaxies or specific SFR thresholds.
The paper should clarify whether any free parameters were adjusted when implementing the MACER prescriptions or if the substitution was parameter-free.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the thoughtful and constructive report. We address each major comment below and will incorporate revisions to strengthen the manuscript where appropriate.

read point-by-point responses

Referee: Abstract: The central claim that similarity in outcomes 'underlines the self-regulated nature of BH feedback' and that 'the accretion rate tends to adjust such that a similar total AGN feedback energy is released' lacks direct supporting evidence, as no comparison of cumulative AGN feedback energy injected or of BH accretion rate time series between the original TNG and MACER-based runs is presented.

Authors: We agree that explicit comparisons of cumulative AGN feedback energy and BH accretion rate time series would provide stronger direct support for the self-regulation interpretation. While the similarity in global galaxy properties is consistent with this picture, we did not include these diagnostics. In the revised manuscript we will add a figure and accompanying discussion showing the time evolution of cumulative feedback energy (and accretion rates) for both models in the cosmological runs. revision: yes
Referee: Cosmological simulations section: The unchanged TNG accretion rate estimator, which was originally calibrated to match observations, may drive the observed similarity in large-scale properties independently of the feedback output change, raising the possibility that the result partly inherits the original calibration rather than demonstrating compensatory self-regulation.

Authors: This is a substantive concern. The accretion estimator is indeed retained from TNG. However, the change in feedback output alters gas thermodynamics and dynamics, which feeds back into the conditions governing subsequent accretion. We will revise the cosmological simulations section to clarify this coupling and to show that, despite the shared estimator, the detailed accretion histories differ between the two models in a manner consistent with compensatory self-regulation. revision: partial
Referee: Idealized elliptical galaxies section: While qualitative improvements in gas density profiles are reported, the abstract provides no quantitative error bars or metrics (e.g., chi-squared fits or profile residuals) to assess the degree of improvement over TNG.

Authors: We acknowledge that quantitative metrics are needed to substantiate the reported improvement in gas density profiles. In the revised manuscript we will add explicit quantitative comparisons (e.g., root-mean-square residuals or chi-squared values) between the simulated profiles and observational data for both the original TNG and MACER-based models. revision: yes

Circularity Check

0 steps flagged

No significant circularity; model comparison is self-contained

full rationale

The paper modifies the IllustrisTNG AGN feedback implementation by swapping in MACER prescriptions for feedback output at high and low accretion rates while leaving the accretion-rate estimator unchanged. It then reports that cosmological runs produce similar SFR density evolution, z=0 stellar mass function, and high-mass M⋆-MBH relation, interpreting this as evidence that accretion self-regulates to yield comparable total feedback energy. This is an empirical outcome of the two simulation suites rather than a derivation that reduces to its inputs by construction. No equations are presented that equate a claimed prediction to a fitted parameter, no uniqueness theorem is invoked via self-citation, and no ansatz is smuggled in. The shared accretion module is explicitly stated, so the similarity is a direct consequence of the experimental design, not a hidden tautology. The result is therefore scored as non-circular.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the assumption that MACER feedback prescriptions can be grafted onto the existing TNG accretion rate formula without introducing new tunable parameters or violating the original calibration. No explicit free parameters are listed in the abstract, but the unchanged accretion estimator implicitly carries all prior TNG calibration choices.

axioms (1)

domain assumption MACER feedback output formulas remain valid when inserted into the TNG numerical scheme and resolution
Invoked when the authors state they adopt MACER prescriptions while keeping the accretion rate estimation unchanged.

pith-pipeline@v0.9.0 · 5614 in / 1462 out tokens · 46133 ms · 2026-05-15T10:20:45.148930+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

Cost.FunctionalEquation washburn_uniqueness_aczel matches

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matches
MATCHES: this paper passage directly uses, restates, or depends on the cited Recognition theorem or module.

the similarity of the outcomes underlines the self-regulated nature of BH feedback: for different feedback energetics, the accretion rate tends to adjust such that a similar total AGN feedback energy is released
Foundation.RealityFromDistinction reality_from_one_distinction echoes

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echoes
ECHOES: this paper passage has the same mathematical shape or conceptual pattern as the Recognition theorem, but is not a direct formal dependency.

Since the feedback efficiency in basic-MACER is lower than in TNG at the same Bondi accretion rate, the feedback process will adjust the accretion rate and make the energy output rate roughly balance the radiative cooling. So the Bondi accretion rate in basic-MACER ends up being higher than in TNG.

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

A systematic study of AGN feedback in a disk galaxy using MACER II: predictions of X-ray surface brightness profiles and comparison with eROSITA observations
astro-ph.GA 2026-03 conditional novelty 5.0

AGN feedback simulations predict X-ray surface brightness profiles that match eROSITA CGM observations out to 100 kpc.