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Feeding or Fleeing: The Impact of Enhanced Early Black Hole Growth on Circumgalactic Clumps at $z > 6$

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Floor van Donkelaar, Lucas Tortora, Debora Sijacki

Astrophysics of Galaxies · Submitted 29 Oct 2026 · 300 references

Pith's verdict: An honest, well-tested two-run comparison showing that the super-Eddington model package produces outward-moving, metal-rich CGM clumps; the causal attribution to the blow-out specifically is the one claim the paper cannot isolate.

T0 · AI review

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CitationDebora Sijacki, Floor van Donkelaar, Lucas Tortora. "Feeding or Fleeing: The Impact of Enhanced Early Black Hole Growth on Circumgalactic Clumps at $z > 6$." arXiv:2610.39692 (2026). https://pith.science/paper/Y7ZBNSMU
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The paper

The paper claims

This paper argues that enhanced early black hole growth drives an AGN blow-out that ejects dense, metal-enriched, relatively cool gas clumps outward through the circumgalactic medium, some beyond the virial radius.

The reading

Two zoom-in simulations of the same massive halo at $z > 6$ — one with standard Eddington-limited black hole growth (Fable) and one with enhanced early growth through earlier seeding and mildly super-Eddington accretion (Fable-SE) — spawn dense circumgalactic clumps of similar mass, size and stellar content, but with very different chemistry and motion. The paper's claim is that the stronger active-galactic-nucleus (AGN) blow-out phase at $z \lesssim 7$ in Fable-SE is accompanied by a population of metal-enriched clumps moving outward through the halo: below $z = 7$, 43 per cent of clump detections are metal-rich versus 9 per cent in Fable, and among stellar candidates born during the blow-out, 31 per cent migrate outward versus 14 per cent, with 52 tracked systems crossing from inside to outside the virial radius (the radius enclosing 200 times the cosmic critical density, roughly 85 kpc here) against none in Fable. The outward-moving systems stay relatively cool and dense and sit in disturbed, neutral-hydrogen-rich gas rather than inside resolved satellite galaxies, which the authors read as the AGN redistributing enriched material through the circumgalactic medium. Inward migration still dominates in both runs, so the paper's conclusion is that dense CGM structures around massive high-redshift galaxies trace both filamentary accretion and feedback-driven evolution: a clump found far from a galaxy does not necessarily have to have formed there. This matters because it connects early black hole growth to the baryon cycle and to the compact, offset, cluster-like structures JWST is finding at cosmic dawn.

What carries the argument

The argument runs on a comparison between two black hole growth recipes, with the clump census carried by a gas-overdensity finder and mesh-based tracking. Fable-SE differs from Fable in five coupled changes: black holes are seeded in haloes down to $10^9\,h^{-1}\,M_\odot$ instead of $5\times10^{10}\,h^{-1}\,M_\odot$; accretion is capped at $f_{\rm Edd} = 2$ instead of the Eddington limit; radio-mode feedback is switched off; the quasar-mode duty cycle is removed so feedback energy is injected continuously; and the quasar-mode coupling is lowered from 10 to 5 per cent. Together these yield the order-of-magnitude heavier black hole and the blow-out phase on which the interpretation rests. The clump population itself is defined by friends-of-friends grouping of gas cells with $\rho_{\rm gas}/\bar{\rho}_{\rm b} \geq 200$ in the annulus 25–105 kpc from the halo centre, requiring at least 16 cells, $M_{\rm gas} \geq 10^6\,M_\odot$, and $0.1 < R_{\rm half,gas} < 15$ kpc; stellar candidates are those clumps that contain stars or satisfy a dense-gas proxy ($n_{\rm H} \geq 0.1$ cm$^{-3}$). Radial tracks are built by matching shared moving-mesh cell identifiers between snapshots, and the net displacement $\Delta r = r_{\rm final} - r_{\rm birth}$ separates inward from outward migration. The blow-out phase itself is characterized in the companion paper Tortora et al. 2026; this paper's machinery measures what happens to dense CGM structures across it.

Extended reading notes

Core claim

On its own terms, the paper's discovery is that accelerating black hole growth in the first billion years changes not just how much gas the halo holds, but what its dense gas structures are made of and how they move. In Fable-SE the central black hole reaches $1.3\times10^{10}\,M_\odot$ by $z = 6$, ten times the fiducial value, and the halo passes through a strong AGN-driven blow-out phase at $z \lesssim 7$. During and after that phase the clump population diverges from Fable: clumps become roughly twice as abundant, the metal-rich fraction ($Z_{\rm gas} \geq 0.32\,Z_\odot$) climbs from 9 to 43 per cent, and a substantial minority of stellar candidates born at $z < 7$ migrate outward (31 per cent versus 14 per cent; 40 versus 5 per cent for clumps tracked over at least four snapshots). Fifty-two stellar-candidate tracks begin inside the virial radius and end outside it, while no Fable track does. The outward-moving Fable-SE clumps are not simply hot debris: their median cold gas fraction is 0.92 versus 0.23, their median gas temperature is $8.9\times10^4$ K versus $2.0\times10^6$ K, they remain dense, and most are not associated with resolved satellite galaxies. The authors conclude that strong early AGN activity redistributes dense, metal-enriched, relatively cool gas structures through the CGM, producing a 'fleeing' population alongside the dominant inward flow of filamentary gas.

Load-bearing premise

The causal story — that the strong AGN-driven blow-out phase, rather than some other aspect of the modified black hole model, produces the extra metal-rich and outward-moving clumps — rests on a comparison that changes five coupled parameters at once (earlier and more numerous seeding, $f_{\rm Edd} = 2$, radio mode off, no duty cycle, 5 per cent coupling) with no ablation run to isolate the blow-out, and the blow-out phase itself is characterized in an unpublished companion paper.

Editorial extensions

If this is right

  • Dense CGM structures around massive $z>6$ galaxies can have two distinct origins: low-metallicity clumps following filamentary infall toward the galaxy, and metal-enriched clumps displaced outward by AGN-driven outflows; a clump's current radius therefore does not reveal where it was born.
  • Strong early black hole growth does not merely empty the halo of cold gas; in Fable-SE it is associated with more numerous, denser, metal-enriched clumps in the CGM, including systems that cross outward beyond the virial radius (52 tracks versus none).
  • The outward-moving systems remain identifiable, relatively cool, dense and locally converging gas structures over the tracked interval, even though they are not strongly self-gravitating on the resolved kiloparsec scale; whether they survive, fragment, or fall back onto the galaxy remains open.
  • Observationally, the model implies metal absorption systems and possibly offset rest-frame UV emission around massive high-redshift galaxies and quasars arising from ejected clumps; the simulated candidates are larger and have lower stellar surface densities than resolved JWST clusters.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • My reading: because the five black hole parameter changes are coupled, the cleanest test of the blow-out attribution — a run that raises only the Eddington cap — is a natural next step the paper does not report, and the result of that run would decide whether 'enhanced growth' or 'the blow-out phase' is the right label for the driver.
  • My extension: if the trend generalizes beyond this single halo, feedback-driven outward clumps would add a third channel, alongside disc fragmentation and filament accretion, for populating the CGM with cluster-scale structures at cosmic dawn; the paper itself notes it studies only one halo, so the generalization is unproven.
  • My extension: because the authors acknowledge the CGM small-scale structure is not converged at their resolution, the natural follow-up is the same halo rerun at higher resolution with a shorter linking length; the two possible outcomes — the fleeing clumps fragment into compact bound clusters or dissolve as numerical overdensities — would respectively strengthen or weaken the link to JWST's compa
Original abstract

The circumgalactic medium (CGM) of massive high-redshift galaxies contains inflowing filamentary gas, recycled material, and feedback-driven outflows. We investigate the formation and evolution of dense CGM clumps in two cosmological zoom-in simulations of the same massive halo at $z > 6$: the fiducial Fable model and the modified Fable-SE model, which includes enhanced early black hole growth through mild super-Eddington accretion. We identify dense gas clumps in the CGM and follow their gas properties, stellar content, and radial evolution across cosmic time. At the resolution probed here, the two simulations show broadly similar distributions of clump gas mass, gas size and associated stellar mass. Instead, the clump populations differ mainly in their abundance, metallicity, and radial evolution. Fable-SE produces substantially more metal-enriched clumps, including an outward-moving population during the strong AGN-driven blow-out phase at $z \lesssim 7$. These systems are associated with disturbed HI-rich gas and relatively high gas densities, linking the increased prevalence of dense, metal-enriched CGM structures in Fable-SE to its stronger AGN-driven blow-out phase. Although inward migration dominates overall, Fable-SE also contains an outward-moving clump population during the blow-out phase, with some clumps moving beyond the virial radius. Our results therefore indicate that the distribution of dense CGM clumps around massive high-redshift galaxies reflects both filamentary accretion and feedback-driven CGM evolution, with strong early AGN activity associated with the outward migration of dense, metal-enriched gas structures containing relatively cool gas.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-10-30: 1 request, 7,145 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.40 · human participants 0.01 · controlled comparison 0.91 · randomized assignment 0.01 · states quantitative result 0.14 · compares with prior results 0.83 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

The circumgalactic medium (CGM) of massive high-redshift galaxies contains inflowing filamentary gas, recycled material, and feedback-driven outflows. We investigate the formation and evolution of dense CGM clumps in two cosmological zoom-in simulations of the same massive halo at $z > 6$: the fiducial Fable model and the modified Fable-SE model, which includes enhanced early black hole growth through mild super-Eddington accretion. We identify dense gas clumps in the CGM and follow their gas properties, stellar content, and radial evolution across cosmic time. At the resolution probed here, the two simulations show broadly similar distributions of clump gas mass, gas size and associated stellar mass. Instead, the clump populations differ mainly in their abundance, metallicity, and radial evolution. Fable-SE produces substantially more metal-enriched clumps, including an outward-moving population during the strong AGN-driven blow-out phase at $z \lesssim 7$. These systems are associated with disturbed HI-rich gas and relatively high gas densities, linking the increased prevalence of dense, metal-enriched CGM structures in Fable-SE to its stronger AGN-driven blow-out phase. Although inward migration dominates overall, Fable-SE also contains an outward-moving clump population during the blow-out phase, with some clumps moving beyond the virial radius. Our results therefore indicate that the distribution of dense CGM clumps around massive high-redshift galaxies reflects both filamentary accretion and feedback-driven CGM evolution, with strong early AGN activity associated with the outward migration of dense, metal-enriched gas structures containing relatively cool gas.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 The circumgalactic medium (CGM) of massive high-redshift galaxies contains inflowing filamentary gas, recycled material, and feedback-driven outflows. background 1.00 0.07 0.02 asserted 1.00
s1 We investigate the formation and evolution of dense CGM clumps in two cosmological zoom-in simulations of the same massive halo at $z > 6$: the fiducial Fable model and the modified Fable-SE model, which includes enhanced early black hole growth through mild super-Eddington accretion. contribution 0.61 0.94 0.03 asserted 0.94
s2 We identify dense gas clumps in the CGM and follow their gas properties, stellar content, and radial evolution across cosmic time. method 0.80 0.96 0.02 asserted 0.93
s3 At the resolution probed here, the two simulations show broadly similar distributions of clump gas mass, gas size and associated stellar mass. result 1.00 0.93 0.04 asserted 0.99
s4 Instead, the clump populations differ mainly in their abundance, metallicity, and radial evolution. result 1.00 0.91 0.10 asserted 1.00
s5 Fable-SE produces substantially more metal-enriched clumps, including an outward-moving population during the strong AGN-driven blow-out phase at $z \lesssim 7$. result 1.00 0.95 0.20 asserted 1.00
s6 These systems are associated with disturbed HI-rich gas and relatively high gas densities, linking the increased prevalence of dense, metal-enriched CGM structures in Fable-SE to its stronger AGN-driven blow-out phase. interpretation 0.82 0.91 0.15 asserted 0.96
s7 Although inward migration dominates overall, Fable-SE also contains an outward-moving clump population during the blow-out phase, with some clumps moving beyond the virial radius. result 1.00 0.93 0.09 asserted 1.00
s8 Our results therefore indicate that the distribution of dense CGM clumps around massive high-redshift galaxies reflects both filamentary accretion and feedback-driven CGM evolution, with strong early AGN activity associated with the outward migration of dense, metal-enriched gas structures containing relatively cool gas. interpretation 0.99 0.94 0.93 hedged possibility 0.94

What kind of paper the classifier reports this is: simulation study 1.00 · evidence from simulation or computation 1.00.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Metallicity-weighted gas density projections of FABLE (left) and FABLE-SE (right) at 𝑧 = 6.25. Each panel covers 220 × 220 physical kpc, with a line-of-sight depth of 220 physical kpc. The colour scale shows ⟨𝜌gas⟩𝑍 = ∫ 𝜌 2 gas𝑍 𝑑𝑙/ ∫ 𝜌gas𝑍 𝑑𝑙 (see also Tortora et al. 2026). The dashed squares indicate the 40 × 40 physical kpc regions shown in the enlarged insets. Red circles mark gas clumps containing stars that are tracked for at least five subsequent snapshots. 𝛼vir = 5𝜎 2 1D𝑅ap 𝐺𝑀gas(< 𝑅ap) , (5) where 𝑀gas(< 𝑅ap) is the gas mass enclosed within the aperture. To characteri
Figure 2. Redshift evolution of the relative abundance of CGM clumps in Fable-SE compared to Fable (left), the fraction of clumps classified as stellar candidates (middle), and the fraction of metal-rich clumps (right). We define metal-rich clumps as those with log10 (𝑍gas/𝑍⊙ ) ≥ −0.5. The horizontal dotted line in the left panel marks equal clump abundances. The grey shaded region indicates the strong AGN-driven blow-out phase at 𝑧 ≲ 7 in Fable-SE. affects only the estimated stellar properties of starless candidates and does not enter the stellar-candidate selection or gas-clump tracking.…
Figure 3. Distribution of gas clump properties in the Fable-SE (purple) and Fable (green) simulations. The panels show the distributions of gas mass, gas half-mass radius, gas surface density (Σgas), and gas metallicity. The shaded purple histograms highlight the metal-rich population in Fable-SE, defined by log10 (𝑍gas/𝑍⊙ ) ≥ −0.5. The shaded distributions are normalised to the total number of Fable-SE clumps, showing their contribution to the full population. 10 3 10 4 Rgas [pc] 10 7 10 8 10 9 10 10 Mgas [M ] aSE = 1.67, = 0.24dex aFABLE = 1.89, = 0.20dex FABLE-SE FABLE Metal-rich FABLE-SE…
Figure 4. The gas mass, 𝑀gas, as a function of gas half-mass radius, 𝑅gas. Grey hexagonal bins show the number density of Fable-SE clumps, with the corresponding colour scale indicated on the right. Black contours show the distribution of Fable clumps, while the purple shaded regions and dashed contours highlight the metal-rich population in Fable-SE, defined by log10 (𝑍gas/𝑍⊙ ) ≥ −0.5. The metal-rich contours are normalised to the peak density of that subset. Solid lines indicate the best-fitting power-law relations for the full Fable-SE (purple) and Fable (green) populations. The labels…
Figure 5. Distributions of stellar mass associated with gas-selected stellar candidates in Fable-SE (purple) and Fable (green). Solid lines show mea￾sured stellar masses for clumps containing stellar particles. Dotted lines show estimated stellar masses for starless candidates satisfying our dense-gas proxy, assuming 𝑀★,est = 0.05 𝑀gas. Both components are normalised to the to￾tal number of plotted stellar-candidate detections in each simulation. These masses refer to gas-selected clumps and need not correspond to individual stellar clusters. sent extended gas structures rather than…
Figure 6. Distribution of net radial migration, 𝑟final − 𝑟birth, for clumps tracked for at least two snapshots. The left panels show all gas clumps, while the right panels show the stellar-candidate sample. The top panels include all birth redshifts, while the bottom panels are restricted to 𝑧birth < 7. Violin plots and overplotted points show the distributions for Fable-SE and Fable, with the horizontal black line marking the mean. Positive values correspond to net outward migration and negative values to net inward migration. The 𝑓out values give the fraction of clumps with 𝑟final − 𝑟birth…
Figure 7. Gas surface density maps centred on the main galaxy for the Fable (top) and Fable-SE (bottom) simulations at different redshifts. Crosses mark stellar candidates, while line segments indicate their subsequent radial displacement over approximately 40 Myr, measured relative to the galaxy centre. Inward￾moving systems are shown in orange and outward-moving systems in red. While inward migration dominates in Fable, Fable-SE shows a larger population of outward-moving clumps, particularly at lower redshifts during the AGN-driven blow-out phase
Figure 8. Birth gas metallicity, log10 (𝑍gas,birth/𝑍⊙ ), as a function of birth radius, 𝑟birth, for the stellar candidates sample in the Fable-SE and Fable runs. Hexagons are colour-coded by the median net radial migration, 𝑟final − 𝑟birth, in each bin. Only clumps with lifetimes of at least two snapshots are included. 3.3.2 Gas properties of migrating clumps The previous sections showed that Fable-SE produces a larger pop￾ulation of outward-moving stellar candidates, particularly during the strong blow-out phase at 𝑧 ≲ 7. We now examine whether these systems remain associated with relatively…
Figure 9. Distributions of gas surface density, Σgas, and volume-weighted hydrogen number density, 𝑛H, for inward- and outward-moving stellar candidates in Fable (top) and Fable-SE (bottom). Filled histograms show inward-moving candidates, while solid outlines show outward-moving candidates. Gas properties are measured at the final identified snapshot. The histograms show the number of clumps per bin, without normalisation. Only candidates born at 𝑧birth < 7 and tracked for at least four snapshots are included. The samples contain 281 inward- and 15 outward-moving candidates in Fable,…
Figure 10. HI gas surface density maps centred on the main galaxy for the Fable (top) and Fable-SE (bottom) simulations, shown at different redshifts. Circles mark outward-moving stellar candidate clumps with lifetimes of at least four snapshots. Together, these results suggest that the outward-moving population in Fable-SE represents extended, relatively cool and dense gas struc￾tures embedded within the disturbed CGM. Although these systems are not resolved as compact stellar clusters, they may contain smaller, unresolved star-forming regions. However, our measurements do not establish…
Figure 11. Stellar surface density, Σ★, as a function of effective radius, 𝑅eff,★, for the stellar candidates sample. Contours show the distribution of simulated clumps in the Fable-SE (purple) and Fable (green) runs. Open circles show JWST clusters at 𝑧 > 6 from Claeyssens et al. (2023); Adamo et al. (2024); Fujimoto et al. (2025); Mowla et al. (2024); Messa et al. (2025). Grey dashed lines indicate constant stellar mass. moving Fable sample is small. Together with the disturbed HI mor￾phology surrounding the galaxy during the blow-out phase in Fable￾SE, this suggests that the stronger early…

Figures reproduced from arXiv:2610.39692 by the authors.

References

Discussion

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