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REVIEW 4 major objections 5 minor 246 references

A galaxy formation simulation that lets dense gas birth a top-heavy stellar IMF produces far-UV luminosities up to four times brighter at z>10, easing the tension between JWST observations and standard galaxy formation models.

Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →

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2026-08-01 21:02 UTC pith:HZYDP4MS

load-bearing objection Honest, careful simulation paper; the headline boost is set by hand, not predicted, but the self-consistent machinery and disclosed caveats make it a serious plausibility study. the 4 major comments →

arxiv 2607.16404 v1 pith:HZYDP4MS submitted 2026-07-17 astro-ph.GA

Cosmological simulations of the high-redshift galaxy population adopting a variable stellar initial mass function

Anna Durrant , Robert A. Crain , Cedric G. Lacey , Joop Schaye , Renske Smit , Andrea Gebek , Matthieu Schaller , Shengdong Lu
show 10 more authors
Evgenii Chaikin Nick Andreadis Maarten Baes Matthew R. Bate Alejandro Ben\'itez-Llambay Carlos S. Frenk Filip Hu\v{s}ko Robert J. McGibbon Sylvia Ploeckinger Alexander J. Richings
This is my paper
classification astro-ph.GA
keywords high-redshift galaxiesinitial mass functiontop-heavy IMFUV luminosity functionJWSTcosmological simulationsgalaxy formationdust attenuation
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

This paper argues that JWST's surprising abundance of UV-bright galaxies at z>10 can be explained within standard cosmology if the stellar initial mass function is not universal. The authors run a 100 cMpc cosmological simulation in which the IMF's high-mass slope becomes progressively top-heavy as the density of the natal gas rises, and they self-consistently adjust supernova feedback, metal yields, and dust production to match. Relative to the same simulation with a fixed Chabrier IMF, early galaxies are up to a factor of ~4 brighter in the far-UV, producing observed magnitudes as bright as M_UV ~ -20 at z=15. The variable-IMF run reproduces the bright end of the observed UV luminosity function at z≥7 better than the fiducial run, while still matching the z=5 stellar mass function and optical luminosity function. A sympathetic reader would see this as a plausible, testable path to reconciling JWST's bright galaxies with standard cosmology.

Core claim

The paper's central claim is that top-heavy star formation in dense gas at early times can lift the UV brightness of high-redshift galaxies enough to match JWST. In the authors' model, the high-mass slope of the IMF varies smoothly from the Kroupa value (-2.3) to a top-heavy value (-1.6) as the natal gas density rises above a pivot of 30 cm^-3. This single modification, implemented self-consistently for CCSN feedback energy, heavy-element yields, and dust ejection, elevates the rest-frame far-UV luminosity of early galaxies by up to a factor of ~4, enabling formation of galaxies with observed brightness M_UV ~ -20 at z=15 compared to -18.5 in the fiducial simulation. The simulation reproduce

What carries the argument

The central object is the density-dependent initial mass function, parameterized as a sigmoid on the high-mass slope α(n_H,birth) = -1.6 + (-2.3+1.6)/(1+(n_H,birth/30 cm^-3)^0.65). It does the work of transforming normal stellar populations into UV-bright, metal-rich, dust-rich ones, and it is what makes the model's feedback energetics mimic the fiducial pressure-dependent feedback while changing the IMF itself.

Load-bearing premise

The load-bearing premise is that the IMF of newborn stars is a deterministic, monotonic function of the density of their natal gas, with the specific parameters (top-heavy slope -1.6, pivot density 30 cm^-3, width 0.65) chosen by hand; if the real IMF variation is weaker, driven by a different physical variable, or even absent, the claimed UV brightening collapses.

What would settle it

Measure the oxygen abundance or dust content of a spectroscopically confirmed z~10 galaxy with M_UV ~ -20. This model predicts about twice the metallicity at fixed stellar mass and about three times the dust mass relative to a universal IMF simulation, so a measurement consistent with normal solar-neighbourhood IMF enrichment (as in the fiducial simulation) would rule out the proposed top-heavy IMF in those galaxies and cast doubt on the whole mechanism.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • A top-heavy IMF in dense gas can, within standard cosmology, produce UV-bright galaxies at z>10 that match JWST counts; the simulated galaxies reach M_UV ~ -20 at z=15 even in a 100 cMpc box.
  • Self-consistent treatment of yields and feedback matters: top-heavy populations inject about twice as much CCSN energy per stellar mass, eject about three times more metals and dust, and the extra dust attenuates the UV boost, reconciling the z=5 UVLF with observations.
  • The model overpredicts the 'knee' of the UVLF at z=9-12 by about half a magnitude, indicating that the degree of top-heaviness in moderate-overdensity galaxies needs tuning, likely via the pivot density.
  • A volume eight times larger (200 cMpc) would, under this model, produce galaxies as bright as M_UV ~ -23 at z=15, covering even the most extreme JWST sources without invoking more exotic explanations.

Where Pith is reading between the lines

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

  • Editorial inference: If the real driver of IMF variation is metallicity or turbulence rather than density, the specific sigmoid mapping is likely wrong, but the qualitative conclusion that early star formation can be top-heavy enough to explain JWST may survive in modified form.
  • Editorial inference: The model predicts that the most UV-luminous z>10 galaxies should be unusually metal-rich (about twice at fixed stellar mass) and dust-rich; upcoming JWST/NIRSpec spectroscopy and ALMA dust continuum can test this directly against the fiducial prediction.
  • Editorial inference: The authors' parameter choice (α_high = -1.6) is tuned to balance a brief UV boost against a post-10 Myr decline; a broader survey of the (α_high, n_H,pivot) plane in smaller boxes would show how robust the UVLF match is to the assumed IMF-density relation.
  • Editorial inference: Extending the simulation to z=0 would check whether the enhanced metal and dust production leaves observable imprints on local galaxy scaling relations, potentially constraining the fraction of stars ever formed from top-heavy populations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

4 major / 5 minor

Summary. The paper presents a new L=100 cMpc cosmological hydrodynamical simulation evolved to z=5 with a modified COLIBRE model in which the high-mass slope of the IMF varies with natal gas density (Eq. 2). Stellar population synthesis (FSPS), nebular emission (CLOUDY), and dust attenuation (SKIRT) are used to produce rest-frame far-UV luminosities, UV luminosity functions, and related observables. The central claim is that a density-dependent, top-heavy IMF at high redshift boosts the intrinsic far-UV luminosities of early galaxies by up to a factor of roughly 4, bringing the bright end of the z>10 UVLF into better agreement with JWST observations than the fiducial Chabrier-IMF COLIBRE simulation, while still approximately reproducing the z=5 galaxy stellar mass function and optical luminosity function. The paper is careful to quantify several systematic effects, including SFH resampling, nebular emission, box-size effects, and Eddington bias, and it explicitly reports the z=9-12 overbrightness and the z=5 metallicity offset.

Significance. If the results are taken at face value, this is a useful proof-of-concept that a top-heavy IMF can alleviate the high-redshift UV-bright galaxy tension within a full cosmological simulation, going beyond semi-analytic models by self-consistently adjusting CCSN feedback energetics, metal yields, and dust production. The analysis chain is technically careful, and the appendices provide valuable quantitative caveats. However, the scientific significance is limited by the fact that the IMF-density relation is heuristic and its parameters are tuned in part to produce the very UV boost that is then presented as the main success. The paper is honest about this circularity, but the headline claim is therefore closer to a consistency check than an independent prediction.

major comments (4)
  1. [§2.2.1, §4.2.4, Fig. 7] The central claim that the variable IMF model 'reproduces the bright end of the observed UVLF more accurately' is weakened by the tuning of Eq. 2. The paper states that α_high=-1.6 was chosen to balance a ~4.4x boost in 1 Myr UV luminosity against a decline after 100 Myr, and that γ=0.65 and n_H,pivot=30 cm^-3 were chosen so that cumulative CCSN energy tracks the fiducial model. Since the bright end of the UVLF responds nearly monotonically to the fraction of top-heavy stellar populations, the z>10 agreement in Fig. 7 is partly built into the parameter choice. A sensitivity scan, even at L50m6, showing the UVLF for, e.g., α_high=-1.8 or a shifted pivot density, is needed to establish predictive content. Without it, the 'demonstrating' language in §5(iii) overstates what is a consistency check.
  2. [§2.2, §2.4] Early non-explosive stellar feedback—radiation pressure, winds, and HII photoheating—is evaluated with a fixed Chabrier IMF at all times, as explicitly noted in §2.2. A top-heavy IMF drastically increases the ionizing photon output and wind/radiation pressure of young populations, which directly affects gas expulsion and subsequent star formation. Since the claimed bright-end UVLF improvement depends on the balance between enhanced UV emission and feedback-regulated star formation, this missing self-consistency is a load-bearing approximation. The paper should at least estimate the magnitude of this effect, for example by comparing the ionizing photon budget or by running a test with early feedback scaled to the variable IMF.
  3. [§4.2.4, Appendix A, Abstract] The abstract states that the variable IMF enables galaxies as bright as M_UV ~ -20 at z=15, and §5(iii) claims alleviation of tension. However, the actual simulated attenuated value is M_UV ~ -19.5, and the brightest observed z~15 sources are near -21, so the L100m6 simulation itself still falls short. The brighter M_UV ~ -23 claim rests on post-processing the fiducial L200m6 simulation under the variable IMF, an approach the authors themselves qualify as approximate. Given that the box-size extrapolation assumes the self-consistent feedback and dust effects are minor at z=15, the abstract and summary should more carefully distinguish the directly simulated result from the post-processed extrapolation.
  4. [§4.2.4, Fig. 7, §5(iv)] The variable IMF model overproduces the 'knee' of the UVLF by roughly 0.5-1 mag at z=9-12, which the paper reports. This is not a fatal flaw, but it is important for the central claim: the model trades one tension for another. The paper is honest about this, but the abstract and §5(iii) emphasize only the bright-end improvement. The conclusion should be framed as a conditional demonstration that a top-heavy IMF can help, not that the current parametrisation is a viable solution without further tuning.
minor comments (5)
  1. [§2.1] Typo: 'stellarparticfles' should be 'stellar particles'.
  2. [Fig. 5 caption] 'vIMF' is used without definition; spell out 'variable IMF'.
  3. [§2.4 and Fig. 2] The terminology 'most top-heavy IMF' is clear, but the axis labels use both α and α_high; ensure consistency between Eq. 1 and Fig. 2 annotations.
  4. [§5(iii)] The magnitudes quoted in the summary text differ slightly from the abstract: the abstract says 'up to M_UV ~ -20' while §5 says 'as bright as M_UV ~ -19.5 (intrinsic -20)'. Please harmonise these statements.
  5. [Data Availability] The statement that data are available 'on reasonable request' and code 'will eventually' be released is acceptable for this journal, but the lack of public access to the variable IMF code limits reproducibility. Consider making the code available at the time of publication.

Circularity Check

2 steps flagged

The headline UV-brightening factor is set by the hand-tuned IMF slope, so the UVLF 'improvement' is partly by construction rather than an independent prediction.

specific steps
  1. fitted input called prediction [Section 2.2.1 (Eq. 2) and Abstract]
    "We adopt a maximum gradient of the high-mass slope of the IMF of α_high=−1.6, on the basis of balancing a boost in the UV luminosity ... The top panel of Fig. 2 shows that α=−1.6 yields stellar populations that are a factor of (≃4.4,1.9) as UV-bright as those formed with a Kroupa IMF ... By allowing a significant fraction of high-redshift star formation to proceed with a top-heavy IMF, the rest-frame far-UV luminosities of early galaxies are elevated by up to a factor of ≃4..."

    The abstract's headline boost (up to a factor of ~4) is not an emergent simulation result but the SSP luminosity boost used to select α_high. Section 2.2.1 explicitly chooses α_high=-1.6 because that slope makes young populations a factor ~4.4 brighter than Kroupa. Since the simulated UV brightening is dominated by this prescribed SSP luminosity boost, the high-z UVLF brightening is an input-to-output mapping of the chosen parameter, not an independent prediction. The paper says it is not calibrating to the UVLF, but the factor quoted in the abstract is nevertheless the calibration choice.

  2. fitted input called prediction [Section 2.2.1 (Eq. 2 parameters) and Section 3 (validation)]
    "The remaining parameters in Eq. 2 were chosen to be γ=0.65 and n_H,pivot=30 cm−3, based on analyses of several L=50 cMpc simulations at m6 resolution, evolved to z=5, that span plausible ranges of these parameters. A primary aim of the variable IMF model was to yield a redshift evolution of the CCSNe energy injected per stellar mass formed that is comparable to that of the fiducial COLIBRE model, a corollary of which is that the variable IMF simulation should reproduce the z=5 galaxy stellar mass function (GSMF) of the fiducial simulation."

    The z=5 GSMF agreement and the cumulative CCSN-energy ratios (0.88, 0.95, 1.3) presented in Section 3 are not independent validations: they are the design target of the parameter choice stated in Section 2.2.1. The paper itself says the GSMF agreement is a 'corollary' of the aim to match CCSN energy, and adds that 'had this not proven the case... it would have been necessary to adjust the variable IMF model'. Thus the validation step is a consistency check with the fitting criterion, not a prediction. It does not, by itself, confirm the high-z UVLF conclusion.

full rationale

The central high-redshift result is only partially circular. The variable-IMF simulation is self-consistent in its feedback, metal yields, and dust treatment, and the comparison of the z>10 UVLF to JWST data is a genuine, non-trivial computation: whether feedback and dust offset the intrinsic UV boost is not fixed by construction. However, the most quoted number in the abstract, 'elevated by up to a factor of ≃4', is exactly the SSP luminosity boost that motivated the choice of α_high=-1.6 in Eq. 2. The bright-end UVLF improvement is therefore substantially built into the model input, not predicted. The z=5 GSMF 'validation' is likewise a corollary of the explicit tuning of γ and n_H,pivot to reproduce fiducial CCSN energy injection. The paper is unusually transparent about this — it calls the density choice heuristic and states that it does not seek to calibrate the IMF to the UVLF — but transparency does not remove the circularity. No load-bearing self-citation chain or imported uniqueness theorem was found; the COLIBRE self-citations are machine-implemented simulations and external benchmarks, which are not the circular element here. Overall, one or more central 'predictions' reduce to fitted inputs, giving a score of 6.

Axiom & Free-Parameter Ledger

4 free parameters · 6 axioms · 0 invented entities

The headline UV boost rests on the density-IMF mapping of Eq. 2 (all four parameters hand-chosen), the single-slope parameterisation of the IMF, and a chain of stellar-evolution assumptions (CCSN threshold at 8 M_sun, no enrichment above 40 M_sun, Chabrier early feedback, no binaries, fixed ionisation parameter). Each is individually plausible and cited, but none is independently measured, and the paper's own Fig. 2 shows the headline ~4x luminosity boost is a direct function of the chosen alpha_high.

free parameters (4)
  • alpha_high = -1.6 (maximum high-mass IMF slope)
    Sets the most top-heavy IMF allowed (Eq. 2). Chosen in §2.2.1 to balance a boost in young-population far-UV luminosity against a decline after ~100 Myr — i.e., selected to produce a large UV brightening.
  • gamma = 0.65 (sigmoid width)
    Width of the density-IMF transition in Eq. 2; chosen from analyses of several L=50 cMpc m6 test simulations evolved to z=5 (§2.2.1).
  • n_H,pivot = 30 cm^-3
    Pivot natal gas density of the sigmoid; sets which gas densities become top-heavy and therefore what fraction of high-z star formation is UV-boosted. Chosen from L=50 cMpc test runs (§2.2.1).
  • f_E = 2 x 10^51 erg per CCSN
    Fixed energy per CCSN in the variable-IMF model, adopted so that top-heavy populations inject roughly the same CCSN energy per stellar mass formed as the fiducial COLIBRE model, whose f_E varies 0.3-4.0 with pressure.
axioms (6)
  • domain assumption All stars with 8 < m/M_sun < 100 are CCSN progenitors injecting ~10^51 erg each; no 'dark deaths' for any of these stars.
    Invoked in the §1 footnote and throughout (Figs. 2-3, §2.2.1); the paper cites Smartt et al. 2009, Heger & Woosley 2010, and Sukhbold et al. 2016 noting this is debated.
  • domain assumption Stars more massive than 40 M_sun do not enrich the ISM with metals or dust.
    Stated in §2.1 and §2.4 ('We assume that stars more massive than 40 M_sun do not enrich their surroundings'); suppresses the metal/dust yields of the most massive stars, which are more numerous in top-heavy IMFs.
  • ad hoc to paper Early (non-explosive) stellar feedback — radiation pressure, winds, HII photoheating — is evaluated with a fixed Chabrier IMF at all times, regardless of the variable IMF.
    Acknowledged in §2.2: 'the energy injection rates in the early stellar feedback model are pre-tabulated, and self-consistently adjusting them... would require a significant change to the code.' A top-heavy IMF would increase ionising photon output and feedback.
  • domain assumption Nebular line and continuum emission is computed with a fixed ionisation parameter log10 U = -2, independent of the IMF.
    §2.4.1; the paper notes a self-consistent approach would couple U to IMF variations, and that U affects the UV continuum slope.
  • ad hoc to paper Only the high-mass slope of the IMF varies; pivot mass, low-mass slope, and mass limits are fixed (0.1-100 M_sun).
    §2.2: 'We do not explore other methods of varying the IMF here for simplicity'; Barber et al. 2018 showed slope and pivot-mass variations give similar results.
  • domain assumption Binary stellar evolution and binary-driven emission are omitted because FSPS binary mode is restricted to a Salpeter IMF.
    §2.4; the paper notes binaries likely matter more for top-heavy IMFs given the high binary fraction of massive stars.

pith-pipeline@v1.3.0-alltime-deepseek · 48527 in / 20634 out tokens · 177793 ms · 2026-08-01T21:02:51.370155+00:00 · methodology

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read the original abstract

JWST surveys reveal a greater space density of high-redshift UV-bright galaxies than predicted by conventional galaxy formation models. We present results from a $L=100$ cMpc cosmological simulation evolved to $z=5$ with a variation of the COLIBRE galaxy formation model that adopts a density-dependent stellar initial mass function (IMF), such that stellar populations formed from dense gas are born with a top-heavy IMF. Crucially, heavy element and dust yields, and supernova feedback energetics, are self-consistently adjusted to the changing IMF. We model UV/optical emission (including nebular emission) from galaxies and its attenuation by dust. By allowing a significant fraction of high-redshift star formation to proceed with a top-heavy IMF, the rest-frame far-UV luminosities of early galaxies are elevated by up to a factor of $\simeq4$ with respect to the fiducial COLIBRE L100m6 simulation, which assumes a universal Chabrier IMF. This enables the formation of galaxies with observed brightness up to $M_{\rm UV} \simeq -20$ at $z=15$ (c.f. $M_{\rm UV} \simeq -18.5$ in the fiducial simulation), illustrating the potential of star formation with a top-heavy IMF to alleviate tensions with JWST data. Later, the boost in far-UV emission is partly offset by attenuation due to increased dust surface densities from i) additional dust grain ejection from core-collapse supernovae and ii) efficient grain growth promoted by more metal-rich interstellar gas. The simulation reproduces the $z=5$ galaxy stellar mass function and rest-frame optical luminosity function with comparable accuracy to the fiducial simulation, and both simulations exhibit UV continuum slopes that are consistent with JWST observations.

Figures

Figures reproduced from arXiv: 2607.16404 by Alejandro Ben\'itez-Llambay, Alexander J. Richings, Andrea Gebek, Anna Durrant, Carlos S. Frenk, Cedric G. Lacey, Evgenii Chaikin, Filip Hu\v{s}ko, Joop Schaye, Maarten Baes, Matthew R. Bate, Matthieu Schaller, Nick Andreadis, Renske Smit, Robert A. Crain, Robert J. McGibbon, Shengdong Lu, Sylvia Ploeckinger.

Figure 1
Figure 1. Figure 1: Common functional forms of the stellar initial mass function (IMF) shown for the mass range 0.1 < 𝑚★ < 100 M⊙ and normalised such that each IMF integrates to 1 M⊙: those of Salpeter (1955, red) and Kroupa (2001, blue); note that the Chabrier (2003) IMF is not shown because it is indistinguishable over this mass range from that of Kroupa (2001). The black curve corresponds to the most top-heavy IMF used in … view at source ↗
Figure 2
Figure 2. Figure 2: Top: The far-UV luminosity of a simple stellar population (SSP) with solar metallicity (𝑍 = 0.0134) at ages (1, 10, 100) Myr (red, cyan and green curves, respectively), as a function of the high-mass slope of the IMF (𝛼, parameterised as Eq. 1), normalised by the far-UV luminosity of a coeval SSP with a Kroupa (2001) IMF. Middle: the mass fraction (black dashed curve) and number (black dotted curve) of the… view at source ↗
Figure 3
Figure 3. Figure 3: Evolution of the following properties of SSPs with Kroupa IMF (red curves) and the most top-heavy IMF used in our model (cyan curves), of solar metallicity (𝑍 = 0.0134) and initial mass 1 M⊙: i) the far-UV luminosity, ii) the UV half-luminosity mass (the mass of the star above, or below, which half of the far-UV luminosity is produced), iii) the mass of the SSP remaining in stars and remnants (solid curves… view at source ↗
Figure 4
Figure 4. Figure 4: Face-on (top) and edge-on (bottom) mock images using JWST NIRCam filters of the most massive galaxy at 𝑧 = 7 in the fiducial COL￾IBRE L100m6 simulation, 𝑀star = 3.8 × 1010 M⊙, SFR = 125.5 M⊙yr−1 , 𝑀dust = 8.0 × 107 M⊙, 𝑅1/2,star = 0.35 pkpc. The images were created by post-processing the simulated galaxy using the radiative transfer code SKIRT. The left panels shows the galaxy in the absence of dust, right… view at source ↗
Figure 5
Figure 5. Figure 5: (Top) Galaxy stellar mass function and (bottom) median gas-phase oxygen abundance as a function of stellar mass, at 𝑧 = 5, of the fiducial and variable IMF simulations (see [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: The far-UV magnitude of central galaxies as a function of their stellar mass (left) and halo mass (right), in the fiducial (red curves) and variable IMF (cyan curves) simulations. The top, middle and bottom panels show the relation at 𝑧 = 5, 10, 15 respectively. Solid curves represent median dust-attenuated UV magnitudes, dashed curves represent dust-free (intrinsic) UV magnitudes, and thin lines are used … view at source ↗
Figure 7
Figure 7. Figure 7: Evolution of the dust-attenuated (solid curves) and intrinsic (dashed curves) rest-frame far-UV luminosity function (UVLF) of the L100m6 fiducial COLIBRE (red curves) and variable IMF (cyan curves) simulations from 𝑧 = 5 (top left) to 𝑧 = 15 (bottom right). Thin lines indicate where magnitude bins are sampled by fewer than 10 galaxies. Black and purple symbols represent observational data, detailed in §4.2… view at source ↗
Figure 8
Figure 8. Figure 8: shows the evolution of the cosmic far-UV luminosity density, 𝜌UV(𝑧), of the fiducial (red curves) and variable IMF (cyan curves) simulations. As in prior figures, dust-attenuated (intrinsic) UV lumi￾nosities are shown using solid (dashed) curves. The UV luminosity density is computed by summing the UV luminosity of all galaxies with magnitudes 𝑀UV < −18. While a fainter brightness thresh￾old of 𝑀UV < −17 i… view at source ↗
Figure 9
Figure 9. Figure 9: The median galaxy dust mass (top) and median galaxy-averaged dust surface density (bottom) as a function of galaxy stellar mass, shown for the fiducial (red) and variable IMF (cyan) simulations at 𝑧 = 5 (solid curves) and 𝑧 = 10 (dashed curves). Note that the inferred stellar mass estimates from observations assume a Solar neighbourhood IMF. Shaded regions denote the 10th to 90th percentile scatter. Thin l… view at source ↗
Figure 10
Figure 10. Figure 10: Correlations between the total UV attenuation of galaxies, 𝐴UV, and the galaxy-averaged dust surface density (left), the intrinsic UV magnitude of galaxies (middle), and attenuated UV magnitude of galaxies (right), in the fiducial (top row) and variable IMF (bottom row) simulations. Underlying two-dimensional histograms show the probability density of galaxies at 𝑧 = 5. Solid curves correspond to the medi… view at source ↗
Figure 11
Figure 11. Figure 11: The median UV continuum slope, 𝛽, as a function of stellar mass (left) and dust-attenuated UV magnitude (right), from the fiducial COLIBRE (red curves) and variable IMF (cyan curves) simulations. In the left panel, solid (dot-dashed) curves correspond to the dust-attenuated (intrinsic) continuum slope. Results are shown at 𝑧 = 5 in the left panel, and at 𝑧 = 5 (solid curves) and 𝑧 = 10 (dashed curves) in … view at source ↗

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Reference graph

Works this paper leans on

246 extracted references · 3 canonical work pages

  1. [1]

    , keywords =

    The impact of magnetic fields on the IMF in star-forming clouds near a supermassive black hole. , keywords =. doi:10.1051/0004-6361/201219628 , archivePrefix =. 1207.5657 , primaryClass =

    Pith/arXiv arXiv

  2. [2]

    arXiv e-prints , keywords =

    A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec 3-15. arXiv e-prints , keywords =

  3. [4]

    Results for a range of clump densities

    Dust survival rates in clumps passing through the Cas A reverse shock - I. Results for a range of clump densities. , keywords =. doi:10.1093/mnras/stz2399 , archivePrefix =. 1908.10875 , primaryClass =

    Pith/arXiv arXiv 1908

  4. [5]

    , keywords =

    Little Red Dots: An Abundant Population of Faint Active Galactic Nuclei at z 5 Revealed by the EIGER and FRESCO JWST Surveys. , keywords =. doi:10.3847/1538-4357/ad2345 , archivePrefix =. 2306.05448 , primaryClass =

    Pith/arXiv arXiv

  5. [6]

    The Journal of Open Source Software , keywords =

    swift-emulator: A Python package for emulation of simulated scaling relations. The Journal of Open Source Software , keywords =. doi:10.21105/joss.04240 , adsurl =

    doi:10.21105/joss.04240

  6. [7]

    , keywords =

    Cosmological N-body simulations with suppressed variance. , keywords =. doi:10.1093/mnrasl/slw098 , archivePrefix =. 1603.05253 , primaryClass =

    Pith/arXiv arXiv

  7. [8]

    , keywords =

    Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions. , keywords =. doi:10.3847/1538-4357/ab7cc9 , archivePrefix =. 1907.13130 , primaryClass =

    Pith/arXiv arXiv 1907

  8. [9]

    , keywords =

    Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies. , keywords =. doi:10.1093/mnras/stx1060 , archivePrefix =. 1705.00941 , primaryClass =

    Pith/arXiv arXiv

  9. [10]

    , keywords =

    Effects of grain growth mechanisms on the extinction curve and the metal depletion in the interstellar medium. , keywords =. doi:10.1093/mnras/stt1997 , archivePrefix =. 1310.4679 , primaryClass =

    Pith/arXiv arXiv

  10. [11]

    , keywords =

    A Long Time Ago in a Galaxy Far, Far Away: A Candidate z 12 Galaxy in Early JWST CEERS Imaging. , keywords =. doi:10.3847/2041-8213/ac966e , archivePrefix =. 2207.12474 , primaryClass =

    Pith/arXiv arXiv 2041

  11. [12]

    , keywords =

    The stellar mass function of quiescent and star-forming galaxies and its dependence on morphology in COSMOS-Web. , keywords =. doi:10.1051/0004-6361/202558022 , archivePrefix =. 2511.05259 , primaryClass =

    arXiv

  12. [13]

    arXiv e-prints , keywords =

    Reinterpreting the puzzling properties of z>6 galaxies within a variable IMF framework. arXiv e-prints , keywords =. doi:10.48550/arXiv.2603.22405 , archivePrefix =. 2603.22405 , primaryClass =

    doi:10.48550/arxiv.2603.22405

  13. [14]

    arXiv e-prints , keywords =

    Direct Evidence for Stellar Initial Mass Function Variation in the Milky Way. arXiv e-prints , keywords =. doi:10.48550/arXiv.2603.23594 , archivePrefix =. 2603.23594 , primaryClass =

    work page doi:10.48550/arxiv.2603.23594

  14. [15]

    , keywords =

    An upper limit to the energy of gamma-ray bursts indicates that GRBs/SNe are powered by magnetars. , keywords =. doi:10.1093/mnras/stu1124 , archivePrefix =. 1406.1209 , primaryClass =

    Pith/arXiv arXiv

  15. [16]

    , keywords =

    In a hot bubble: why does superbubble feedback work, but isolated supernovae do not?. , keywords =. doi:10.1093/mnras/stu1307 , archivePrefix =. 1402.6695 , primaryClass =

    Pith/arXiv arXiv

  16. [17]

    , keywords =

    Comparing models for IMF variation across cosmological time in Milky Way-like galaxies. , keywords =. doi:10.1093/mnras/stx2067 , archivePrefix =. 1702.04431 , primaryClass =

    Pith/arXiv arXiv

  17. [18]

    , keywords =

    On the shape and evolution of a cosmic-ray-regulated galaxy-wide stellar initial mass function. , keywords =. doi:10.1093/mnras/sty1768 , archivePrefix =. 1807.01319 , primaryClass =

    Pith/arXiv arXiv

  18. [19]

    , keywords =

    Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time. , keywords =. doi:10.1038/s41586-018-0196-x , archivePrefix =. 1806.01280 , primaryClass =

    Pith/arXiv arXiv

  19. [20]

    , keywords =

    Star formation in the outskirts of DDO 154: a top-light IMF in a nearly dormant disc. , keywords =. doi:10.1093/mnras/sty1006 , archivePrefix =. 1804.07072 , primaryClass =

    Pith/arXiv arXiv

  20. [22]

    , keywords =

    The importance of black hole repositioning for galaxy formation simulations. , keywords =. doi:10.1093/mnras/stac1339 , archivePrefix =. 2109.01489 , primaryClass =

    Pith/arXiv arXiv

  21. [23]

    , keywords =

    Bondi-Hoyle Accretion in a Turbulent Medium. , keywords =. doi:10.1086/498844 , archivePrefix =. astro-ph/0510410 , primaryClass =

    Pith/arXiv arXiv

  22. [24]

    , keywords =

    Spurious heating of stellar motions in simulated galactic discs by dark matter halo particles. , keywords =. doi:10.1093/mnras/stab2770 , archivePrefix =. 2105.03561 , primaryClass =

    Pith/arXiv arXiv

  23. [25]

    Galaxy formation as a function of large-scale environment

    Galaxies-intergalactic medium interaction calculation - I. Galaxy formation as a function of large-scale environment. , keywords =. doi:10.1111/j.1365-2966.2009.15402.x , archivePrefix =. 0906.4350 , primaryClass =

    arXiv 2009

  24. [26]

    Environmental dependence of high-redshift galaxy evolution

    First Light And Reionization Epoch Simulations (FLARES) - I. Environmental dependence of high-redshift galaxy evolution. , keywords =. doi:10.1093/mnras/staa3360 , archivePrefix =. 2004.07283 , primaryClass =

    Pith/arXiv arXiv 2004

  25. [27]

    , keywords =

    Predictions for deep galaxy surveys with JWST from CDM. , keywords =. doi:10.1093/mnras/stx2897 , archivePrefix =. 1702.02146 , primaryClass =

    Pith/arXiv arXiv

  26. [28]

    , keywords =

    A unified multiwavelength model of galaxy formation. , keywords =. doi:10.1093/mnras/stw1888 , archivePrefix =. 1509.08473 , primaryClass =

    Pith/arXiv arXiv

  27. [29]

    , keywords =

    The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys. , keywords =. doi:10.1093/mnras/stad2419 , archivePrefix =. 2306.04024 , primaryClass =

    Pith/arXiv arXiv

  28. [30]

    , keywords =

    Galaxy and Mass Assembly (GAMA): the star formation rate dependence of the stellar initial mass function. , keywords =. doi:10.1111/j.1365-2966.2011.18800.x , archivePrefix =. 1104.2379 , primaryClass =

    arXiv 2011

  29. [31]

    , keywords =

    Variations of the initial mass function in semi-analytical models. , keywords =. doi:10.1093/mnras/stu1078 , archivePrefix =. 1405.7699 , primaryClass =

    Pith/arXiv arXiv

  30. [32]

    , keywords =

    Simulating a metallicity-dependent initial mass function: consequences for feedback and chemical abundances. , keywords =. doi:10.1093/mnras/sty2688 , archivePrefix =. 1710.04222 , primaryClass =

    Pith/arXiv arXiv

  31. [33]

    , keywords =

    Can the faint submillimetre galaxies be explained in the cold dark matter model?. , keywords =. doi:10.1111/j.1365-2966.2004.08553.x , archivePrefix =. astro-ph/0406069 , primaryClass =

    arXiv 2004

  32. [34]

    The Stellar Initial Mass Function (38th Herstmonceux Conference) , year = 1998, editor =

    Overview: The Initial Mass Function in Galaxies. The Stellar Initial Mass Function (38th Herstmonceux Conference) , year = 1998, editor =

    1998

  33. [35]

    , keywords =

    Reconciling M/L Ratios Across Cosmic Time: a Concordance IMF for Massive Galaxies. , keywords =. doi:10.3847/2041-8213/ad77b8 , archivePrefix =. 2407.06281 , primaryClass =

    Pith/arXiv arXiv 2041

  34. [36]

    arXiv e-prints , keywords =

    Bottom-heavy initial mass functions reveal hidden mass in early galaxies. arXiv e-prints , keywords =. doi:10.48550/arXiv.2601.20864 , archivePrefix =. 2601.20864 , primaryClass =

    doi:10.48550/arxiv.2601.20864

  35. [37]

    , year = 1997, month = may, volume =

    On the Stellar Population and Star-Forming History of the Orion Nebula Cluster. , year = 1997, month = may, volume =. doi:10.1086/118389 , adsurl =

    doi:10.1086/118389 1997

  36. [38]

    , keywords =

    The Initial Mass Function and Massive Star Evolution in the OB Associations of the Northern Milky Way. , keywords =. doi:10.1086/176474 , adsurl =

    work page doi:10.1086/176474

  37. [39]

    , keywords =

    Starburst Modeling of M82: Test Case for a Biased Initial Mass Function. , keywords =. doi:10.1086/172904 , adsurl =

    work page doi:10.1086/172904

  38. [40]

    , keywords =

    The Stellar Initial Mass Function. , keywords =

  39. [41]

    arXiv e-prints , keywords =

    MEGATRON: Reproducing the Diversity of High-Redshift Galaxy Spectra with Cosmological Radiation Hydrodynamics Simulations. arXiv e-prints , keywords =. doi:10.48550/arXiv.2510.05201 , archivePrefix =. 2510.05201 , primaryClass =

    doi:10.48550/arxiv.2510.05201

  40. [42]

    and Michel-Dansac, Leo and Ocvirk, Pierre , journal =

    Katz, Harley and Rosdahl, Joki and Kimm, Taysun and Blaizot, Jeremy and Choustikov, Nicholas and Farcy, Marion and Garel, Thibault and Haehnelt, Martin G. and Michel-Dansac, Leo and Ocvirk, Pierre , journal =. The. doi:10.21105/astro.2309.03269 , year =

    Pith/arXiv arXiv

  41. [43]

    , keywords =

    The Initial Mass Function of Early-Type Galaxies. , keywords =. doi:10.1088/0004-637X/709/2/1195 , archivePrefix =. 0911.3392 , primaryClass =

    Pith/arXiv arXiv

  42. [44]

    The Stellar Initial Mass Function in Early-type Galaxies From Absorption Line Spectroscopy. II. Results. , keywords =. doi:10.1088/0004-637X/760/1/71 , archivePrefix =. 1205.6473 , primaryClass =

    Pith/arXiv arXiv

  43. [45]

    , keywords =

    SPIDER VIII - constraints on the stellar initial mass function of early-type galaxies from a variety of spectral features. , keywords =. doi:10.1093/mnras/stt943 , archivePrefix =. 1305.2273 , primaryClass =

    Pith/arXiv arXiv

  44. [46]

    Calibrated, cosmological hydrodynamical simulations with variable

    Barber, Christopher and Crain, Robert A and Schaye, Joop , journal=. Calibrated, cosmological hydrodynamical simulations with variable. 2018 , publisher=

    2018

  45. [47]

    Calibrated, cosmological hydrodynamical simulations with variable

    Barber, Christopher and Schaye, Joop and Crain, Robert A , journal=. Calibrated, cosmological hydrodynamical simulations with variable. 2019 , publisher=

    2019

  46. [48]

    , author=

    The luminosity function and stellar evolution. , author=. Astrophysical Journal, vol. 121, p. 161 , volume=

  47. [49]

    Monthly Notices of the Royal Astronomical Society , volume=

    On the variation of the initial mass function , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2001 , publisher=

    2001

  48. [50]

    Publications of the Astronomical Society of the Pacific , volume=

    Galactic Stellar and Substellar Initial Mass Function , author=. Publications of the Astronomical Society of the Pacific , volume=. 2003 , publisher=

    2003

  49. [51]

    Annual Review of Astronomy and Astrophysics , volume=

    Evidence for initial mass function variation in massive early-type galaxies , author=. Annual Review of Astronomy and Astrophysics , volume=. 2020 , publisher=

    2020

  50. [52]

    Chemical evolution of elliptical galaxies with a variable

    Yan, Zhiqiang and Jerabkova, Tereza and Kroupa, Pavel and Vazdekis, Alejandro , journal=. Chemical evolution of elliptical galaxies with a variable. 2019 , publisher=

    2019

  51. [53]

    Stellar mass functions and implications for a variable

    Bernardi, M and Sheth, RK and Fischer, JL and Meert, A and Chae, KH and Dominguez-Sanchez, H and Huertas-Company, M and Shankar, F and Vikram, V , journal=. Stellar mass functions and implications for a variable. 2018 , publisher=

    2018

  52. [54]

    Implications of a variable

    Clauwens, Bart and Schaye, Joop and Franx, Marijn , journal=. Implications of a variable. 2016 , publisher=

    2016

  53. [55]

    An assessment of the evidence from

    Clauwens, Bart and Schaye, Joop and Franx, Marijn , journal=. An assessment of the evidence from. 2015 , publisher=

    2015

  54. [56]

    Monthly Notices of the Royal Astronomical Society , volume=

    The chemical evolution of galaxies with a variable integrated galactic initial mass function , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2015 , publisher=

    2015

  55. [57]

    Monthly Notices of the Royal Astronomical Society , volume=

    Initial mass function variability from the integrated light of diverse stellar systems , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2023 , publisher=

    2023

  56. [58]

    Nature , volume=

    Systematic variation of the stellar initial mass function in early-type galaxies , author=. Nature , volume=. 2012 , publisher=

    2012

  57. [59]

    Cappellari, Michele and Scott, Nicholas and Alatalo, Katherine and Blitz, Leo and Bois, Maxime and Bournaud, Fr. The. Monthly Notices of the Royal Astronomical Society , volume=. 2013 , publisher=

    2013

  58. [60]

    Stress testing

    Boylan-Kolchin, Michael , journal=. Stress testing. 2023 , publisher=

    2023

  59. [61]

    Monthly Notices of the Royal Astronomical Society , volume=

    Nebular dominated galaxies: insights into the stellar initial mass function at high redshift , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2024 , publisher=

    2024

  60. [62]

    Schaye, Joop and Crain, Robert A and Bower, Richard G and Furlong, Michelle and Schaller, Matthieu and Theuns, Tom and Dalla Vecchia, Claudio and Frenk, Carlos S and McCarthy, IG and Helly, John C and others , journal=. The. 2015 , publisher=

    2015

  61. [63]

    Crain, Robert A and Schaye, Joop and Bower, Richard G and Furlong, Michelle and Schaller, Matthieu and Theuns, Tom and Dalla Vecchia, Claudio and Frenk, Carlos S and McCarthy, Ian G and Helly, John C and others , journal=. The. 2015 , publisher=

    2015

  62. [64]

    Simulating galaxy formation with the

    Pillepich, Annalisa and Springel, Volker and Nelson, Dylan and Genel, Shy and Naiman, Jill and Pakmor, R. Simulating galaxy formation with the. Monthly Notices of the Royal Astronomical Society , volume=. 2018 , publisher=

    2018

  63. [65]

    Monthly Notices of the Royal Astronomical Society , volume=

    First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2019 , publisher=

    2019

  64. [66]

    Monthly Notices of the Royal Astronomical Society , volume=

    SIMBA: Cosmological simulations with black hole growth and feedback , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2019 , publisher=

    2019

  65. [67]

    Monthly Notices of the Royal Astronomical Society , volume=

    Dancing in the dark: galactic properties trace spin swings along the cosmic web , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2014 , publisher=

    2014

  66. [68]

    Annual Review of Astronomy and Astrophysics , volume=

    A universal stellar initial mass function? A critical look at variations , author=. Annual Review of Astronomy and Astrophysics , volume=. 2010 , publisher=

    2010

  67. [69]

    The Astrophysical Journal Letters , volume=

    Mart. The Astrophysical Journal Letters , volume=. 2015 , publisher=

    2015

  68. [70]

    The Astrophysical Journal , volume=

    The evolution of the elemental abundances in the gas and dust phases of the galaxy , author=. The Astrophysical Journal , volume=. 1998 , publisher=

    1998

  69. [71]

    Cappellari, Michele and McDermid, Richard M and Alatalo, Katherine and Blitz, Leo and Bois, Maxime and Bournaud, Fr. The. Monthly Notices of the Royal Astronomical Society , volume=. 2013 , publisher=

    2013

  70. [72]

    Monthly Notices of the Royal Astronomical Society , volume=

    Tests of subgrid models for star formation using simulations of isolated disc galaxies , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2024 , publisher=

    2024

  71. [73]

    Colours and luminosities of z= 0.1 galaxies in the

    Trayford, James W and Theuns, Tom and Bower, Richard G and Schaye, Joop and Furlong, Michelle and Schaller, Matthieu and Frenk, Carlos S and Crain, Robert A and Vecchia, Claudio Dalla and McCarthy, Ian G , journal=. Colours and luminosities of z= 0.1 galaxies in the. 2015 , publisher=

    2015

  72. [74]

    Monthly Notices of the Royal Astronomical Society , volume=

    Stellar population synthesis at the resolution of 2003 , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2003 , publisher=

    2003

  73. [75]

    The propagation of uncertainties in stellar population synthesis modeling. I. The relevance of uncertain aspects of stellar evolution and the initial mass function to the derived physical properties of galaxies , author=. The Astrophysical Journal , volume=. 2009 , publisher=

    2009

  74. [76]

    The astrophysical journal , volume=

    The global Schmidt law in star-forming galaxies , author=. The astrophysical journal , volume=. 1998 , publisher=

    1998

  75. [77]

    Nature , volume=

    Spectroscopic confirmation of two luminous galaxies at a redshift of 14 , author=. Nature , volume=. 2024 , publisher=

    2024

  76. [78]

    Monthly Notices of the Royal Astronomical Society , volume=

    A comparison of pre-existing CDM predictions with the abundance of JWST galaxies at high redshift , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2025 , publisher=

    2025

  77. [79]

    Monthly Notices of the Royal Astronomical Society , volume=

    Schaller, Matthieu and Borrow, Josh and Draper, Peter W and Ivkovic, Mladen and McAlpine, Stuart and Vandenbroucke, Bert and Bah. Monthly Notices of the Royal Astronomical Society , volume=. 2024 , publisher=

    2024

  78. [80]

    2022 , publisher=

    Borrow, Josh and Schaller, Matthieu and Bower, Richard G and Schaye, Joop , journal=. 2022 , publisher=

    2022

  79. [81]

    Higher order initial conditions for mixed baryon--

    Hahn, Oliver and Rampf, Cornelius and Uhlemann, Cora , journal=. Higher order initial conditions for mixed baryon--. 2021 , publisher=

    2021

  80. [82]

    Monthly Notices of the Royal Astronomical Society , volume=

    Higher order initial conditions with massive neutrinos , author=. Monthly Notices of the Royal Astronomical Society , volume=. 2022 , publisher=

    2022

Showing first 80 references.