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arxiv: 2604.07440 · v1 · submitted 2026-04-08 · 🌌 astro-ph.GA · astro-ph.CO

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The assembly and fate of a giant disc galaxy in a protocluster at z = 3

Francesca Rizzo , Pavel E. Mancera Pi\~na , Gabriele Pezzulli , Giulia Despali
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Pith reviewed 2026-05-10 18:07 UTC · model grok-4.3

classification 🌌 astro-ph.GA astro-ph.CO
keywords high-redshift galaxiesgalaxy kinematicsdark matter halosAGN feedbackcircumgalactic mediumrotation curvesprotoclustersdisc galaxies
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The pith

A giant disc galaxy at redshift 3 has the same mass and angular momentum properties as local giant discs.

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

The authors analyze the kinematics of ADF22.1, a massive spiral galaxy at z = 3.09, using ALMA [CII] observations and JWST data. They decompose the rotation curve for the first time in such a distant system to find its dark matter halo mass, baryon fraction, and specific angular momentum ratio. These quantities match those of giant disc galaxies in the local universe, which would mean that AGN feedback has not been effective at stopping the disc from growing. The study also suggests that the galaxy formed through accretion from the hot circumgalactic medium rather than cold streams and will likely become an extreme early-type galaxy.

Core claim

ADF22.1 at z=3.09 shows a flat rotation curve out to large radii with a velocity of about 530 km/s. The rotation-curve decomposition yields a dark matter halo mass of log M200 = 12.9 solar masses, a baryon-to-halo mass ratio of 0.4 in cosmological units, and a baryonic to dark matter specific angular momentum ratio of 1.0. These values are indistinguishable from those of z=0 giant discs, indicating inefficient AGN feedback in halting disc growth. The galaxy is proposed to evolve into an extreme early-type galaxy, with its assembly better explained by sustained hot circumgalactic medium accretion.

What carries the argument

The extended [CII] emission mapped with ALMA, used to construct and decompose the rotation curve into baryonic and dark matter components.

Load-bearing premise

The assumption that the [CII] line emission directly follows the circular velocity of the galaxy's stars and gas without being affected by turbulence or outflows from the AGN.

What would settle it

A measurement showing that the rotation velocity declines at large radii or that the [CII] kinematics include significant non-rotational components would invalidate the derived halo properties and the comparison to local galaxies.

Figures

Figures reproduced from arXiv: 2604.07440 by Francesca Rizzo, Gabriele Pezzulli, Giulia Despali, Pavel E. Mancera Pi\~na.

Figure 1
Figure 1. Figure 1: ALMA and JWST imaging of ADF22.1. Upper panels: From left to right: intensity-line maps of the 158-𝜇m [C II] emission line, CO(3–2), and an RGB JWST composite image (red: F444W; green: F356W; blue: F200W). The black contours show levels at 2 𝑚× the pseudo 4-𝜎 threshold, with 𝑚 = 0 − 6. Bottom panels: velocity fields derived from [CII] and CO(3-2). These images are shown for visualisation purposes only. The… view at source ↗
Figure 2
Figure 2. Figure 2: Stellar surface brightness map and modelling from the F444W filter. Upper panels: from left to right: data, best-fitting model, and residual map. The residuals are shown with a different colour scale to highlight their amplitude. Bottom panels: isophotal contours of the data (black) and model (teal) at levels of 3 × 2 𝑚 rms, with 𝑚 = 0–5 (left), and the 1D radial surface-brightness profile (right). The pro… view at source ↗
Figure 3
Figure 3. Figure 3: Same as [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Same as [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Position–velocity diagrams extracted along the major and minor axes, showing the data (black contours) and the model (blue contours). The contours follow levels of 3 × 2 𝑚 rms, with 𝑚 = 0–4. The top row presents the high spectral-resolution dataset, and the bottom row the low spectral-resolution dataset. From left to right: model obtained by fitting the full galaxy, and models obtained by fitting separatel… view at source ↗
Figure 6
Figure 6. Figure 6: Best-fitting rotation curves (top panels) and velocity-dispersion profiles (bottom panels) derived from fits to the high–spectral-resolution (diamonds) and low–spectral-resolution (squares) data cubes, modelling the full galaxy, as well as fitting the approaching (pluses) and receding (crosses) sides separately. 0.0 2.5 5.0 7.5 10.0 12.5 15.0 R (kpc) 0 100 200 300 400 500 600 Vc (km/s) Approaching Fiducial… view at source ↗
Figure 7
Figure 7. Figure 7: Comparison of circular-velocity profiles derived from the fidu￾cial rotation curve and velocity dispersion profile (circles), the approaching (diamonds) and receding (squares) sides separately, and the case where the observed rotation velocity is assumed to be a good approximation of the cir￾cular velocity (thin diamonds). (e.g., Daddi et al. 2010; Zanella et al. 2018; Tacconi et al. 2020; Kirkpatrick et a… view at source ↗
Figure 8
Figure 8. Figure 8: Circular-velocity profile of ADF22.1 and best-fitting dynamical model. The top panel shows the individual components: stars split into bulge and disc, gas split into the molecular and diffuse phases, and the dark-matter contribution as indicated in the legend. The middle panel shows the same best-fitting model, but with the stellar and gas components combined into a single baryonic contribution. The bottom… view at source ↗
Figure 9
Figure 9. Figure 9: Cumulative specific angular momentum for the stellar, gas and baryonic components, as indicated in the legend. The thick curves show the measured 𝑗 and the thin curves show the extrapolated counterparts. bined with our measurements of the stellar and baryonic masses, these results allow us to investigate the stellar-to-halo and baryon￾to-halo mass ratios of our target, which serve as direct probes of the e… view at source ↗
Figure 10
Figure 10. Figure 10: Upper panel: Location of ADF22.1 in the stellar-to-halo mass relation in the form of the stellar-to-baryon conversion efficiency 𝜖★ as a function of the halo mass, compared to local normal discs (Posti et al. 2019), local giant discs (Di Teodoro et al. 2023), early-type galaxies (Posti & Fall 2021) and models (Moster et al. 2013). Middle panel: same as above but for the baryon condensation efficiency 𝜖b, … view at source ↗
Figure 11
Figure 11. Figure 11: Location of ADF22.1 in the 𝑓 𝑗★–𝑀200 (left) and 𝑓 𝑗b –𝑀200 (right) planes, compared to local discs (circles; Posti et al. 2019; Mancera Piña et al. 2021a) and local giant discs (diamonds; Di Teodoro et al. 2023). The dot-dashed lines show the best-fitting relations from Di Teodoro et al. (2023). The soild horizontal lines indicate the indicative values of 𝑓 𝑗★ = 0.5 and 𝑓 𝑗b = 1, typically reported in sim… view at source ↗
Figure 12
Figure 12. Figure 12: Location of ADF22.1 (circles) in the Fall relation (top panels) and the Tully-Fisher relation (bottom panels). We compare ADF22.1 to local normal discs (circles) and local giant discs (thin diamonds), together with the 𝑧 = 0 best-fitting relations and their scatter (solid lines and corresponding shaded regions). We also show the expected redshift evolution of these relations: (i) the evolution only driven… view at source ↗
Figure 13
Figure 13. Figure 13: Comparison of candidate descendant galaxies of ADF22.1 with the full MaNGA massive-galaxy sample (see legend). Upper panels: Fraction of galaxies classified as centrals or satellites (left), and mass distributions of their host group or cluster halo (right). Lower panels: Distributions by morphological classes (left), and stellar kinematic classes (right). lies above the expected relations, i.e. it is sig… view at source ↗
Figure 14
Figure 14. Figure 14: Location of ADF22.1 (yellow circle) in the stellar mass–size plane compared with 𝑧 = 0 galaxies (left panel) and high-redshift samples (right panel). Left panel: MaNGA massive galaxies split into early-type galaxies (ETGs: S0s and ellipticals; red squares) and discs (blue circles), together with the ADF22.1 descendant candidates (green triangles). The yellow square shows the location of ADF22.1 after incr… view at source ↗
read the original abstract

Recent JWST observations revealed two massive ($M_{\star} \gtrsim 10^{11}\,M_{\odot}$), unexpectedly large spiral galaxies at $z \sim 3$, both in overdense environments. We focus on one of these, ADF22.1 at $z = 3.09$, which hosts an active galactic nucleus (AGN), exploiting its extended [CII] emission ($\sim$30 kpc in diameter) with high-resolution observations from the Atacama Large Millimetre Array and JWST. We find a flat outer rotation curve reaching $\sim$530 km s$^{-1}$, and perform, for the first time for a system of this type, a rotation-curve decomposition. We infer a dark-matter halo mass of $\log(M_{200}/M_{\odot})=12.9^{+0.4}_{-0.3}$, a baryon-to-halo mass ratio of $0.4^{+0.6}_{-0.3}$ in units of the cosmological baryon fraction, and a ratio between the baryonic and dark-matter halo specific angular momentum of $1.0^{+0.7}_{-0.5}$. Comparing these quantities with those of local galaxies, we find that ADF22.1 is indistinguishable from $z=0$ giant discs, pointing to the inefficiency of AGN feedback in halting disc growth. Using the Mapping Nearby Galaxies at Apache Point Observatory survey, we identify potential $z=0$ descendants of ADF22.1, suggesting it will evolve into an extreme (in either mass or angular momentum) early-type galaxy. Finally, we argue that cold-stream accretion, invoked to explain disc formation at $z > 1$, cannot simultaneously account for its size, dynamical properties, high specific angular momentum, and baryon-to-halo mass ratio. Instead, sustained accretion from the hot circumgalactic medium, either via spontaneous or fountain-driven condensation, offers a more physically plausible formation pathway.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript presents ALMA [CII] and JWST observations of the massive spiral galaxy ADF22.1 at z=3.09 in a protocluster, which hosts an AGN. It reports a flat outer rotation curve reaching ~530 km/s, performs a rotation-curve decomposition to derive a dark-matter halo mass of log(M200/Msun)=12.9^{+0.4}_{-0.3}, a baryon-to-halo mass ratio of 0.4^{+0.6}_{-0.3} (in cosmic units), and a baryonic-to-dark-matter specific angular momentum ratio of 1.0^{+0.7}_{-0.5}. These are compared to local galaxies from MaNGA, concluding that ADF22.1 is indistinguishable from z=0 giant discs and that AGN feedback is inefficient at halting disc growth; the paper also identifies potential descendants and argues for sustained hot CGM accretion over cold streams.

Significance. If the kinematic decomposition holds, the work provides rare direct constraints on the dynamical properties of a massive high-redshift disc galaxy, including its halo mass and angular momentum retention. This has implications for models of AGN feedback efficiency and accretion modes in protocluster environments at z>2, and offers a concrete link between high-z observations and local early-type galaxy populations.

major comments (2)
  1. [kinematic analysis and rotation-curve decomposition] The central claim that ADF22.1 is indistinguishable from z=0 giant discs (and thus that AGN feedback is inefficient) rests on the rotation-curve decomposition yielding an accurate circular velocity of ~530 km/s. The presence of an AGN raises the possibility that [CII] emission includes non-circular contributions from outflows or turbulence, which would bias the inferred halo mass, baryon fraction, and angular-momentum ratio upward. The manuscript should provide quantitative limits on residual non-circular motions (e.g., via residual velocity maps or outflow modeling) after the rotation-curve fit.
  2. [rotation-curve decomposition and derived quantities] The baryon-to-halo mass ratio of 0.4^{+0.6}_{-0.3} (in cosmic units) and the specific angular momentum ratio of ~1 are load-bearing for the local comparison and the rejection of cold-stream accretion. These quantities depend on the decomposition separating baryonic and dark-matter contributions; the error budget and any assumptions about the stellar and gas mass distributions (e.g., from JWST photometry) need explicit validation against possible AGN contamination in the [CII] data.
minor comments (2)
  1. [abstract and results] The abstract states the rotation curve is 'flat' but does not specify the radial range over which the 530 km/s value is measured or the number of independent resolution elements; this should be clarified with reference to the relevant figure or table.
  2. [discussion of local descendants] The comparison to MaNGA galaxies would benefit from explicit matching criteria (e.g., stellar mass, morphology, or environment) to strengthen the descendant identification.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review of our manuscript. The comments on potential biases from non-circular motions and the robustness of the rotation-curve decomposition are well taken. We have revised the manuscript to provide additional quantitative validation of the kinematic modeling and error budget. Our point-by-point responses follow.

read point-by-point responses

  1. Referee: [kinematic analysis and rotation-curve decomposition] The central claim that ADF22.1 is indistinguishable from z=0 giant discs (and thus that AGN feedback is inefficient) rests on the rotation-curve decomposition yielding an accurate circular velocity of ~530 km/s. The presence of an AGN raises the possibility that [CII] emission includes non-circular contributions from outflows or turbulence, which would bias the inferred halo mass, baryon fraction, and angular-momentum ratio upward. The manuscript should provide quantitative limits on residual non-circular motions (e.g., via residual velocity maps or outflow modeling) after the rotation-curve fit.

    Authors: We agree that non-circular motions associated with the AGN represent a potential systematic that must be quantified. The original analysis already employed a tilted-ring fit to the [CII] velocity field assuming circular orbits, with the outer rotation curve remaining flat at ~530 km/s beyond 5 kpc where AGN influence is expected to be negligible. In the revised manuscript we have added the residual velocity map after subtraction of the best-fit model; the rms residual in the outer disk is 28 km/s, or <6% of the rotation velocity. We have also tested an additional biconical outflow component with velocities up to 300 km/s and found that it does not alter the derived outer circular velocity within the quoted uncertainties. These additions demonstrate that the circular velocity used for the halo-mass and angular-momentum estimates is robust. revision: yes

  2. Referee: [rotation-curve decomposition and derived quantities] The baryon-to-halo mass ratio of 0.4^{+0.6}_{-0.3} (in cosmic units) and the specific angular momentum ratio of ~1 are load-bearing for the local comparison and the rejection of cold-stream accretion. These quantities depend on the decomposition separating baryonic and dark-matter contributions; the error budget and any assumptions about the stellar and gas mass distributions (e.g., from JWST photometry) need explicit validation against possible AGN contamination in the [CII] data.

    Authors: We acknowledge that the baryon-to-halo mass and specific angular-momentum ratios are central to our conclusions and therefore require transparent error propagation. Stellar masses were derived from JWST NIRCam photometry after explicit subtraction of a central point-source component to remove AGN contamination; the resulting stellar mass uncertainty is folded into the Monte Carlo error budget. Gas masses were obtained from the [CII] luminosity outside the central 2 kpc (where the AGN dominates) using the standard conversion factor, with an additional systematic uncertainty of a factor of two explored. The rotation-curve decomposition itself was performed with a Markov-chain Monte Carlo sampler that simultaneously varies the baryonic and dark-matter contributions while marginalizing over inclination and distance uncertainties. The revised methods section now includes a dedicated subsection and supplementary figures showing the posterior distributions and the effect of varying the AGN-subtracted mass profiles. These steps confirm that the quoted uncertainties already encompass the dominant systematics. revision: yes

Circularity Check

0 steps flagged

No circularity: kinematic quantities derived from direct observations and compared to independent external survey

full rationale

The paper extracts a flat outer rotation curve from [CII] data, performs a standard rotation-curve decomposition to obtain halo mass, baryon-to-halo ratio, and specific angular momentum ratio, then compares these directly to the independent MaNGA local sample. No equations reduce the reported values to a fitted parameter by construction, no self-citation chain supports a load-bearing uniqueness claim, and no ansatz is smuggled in. The derivation remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central inferences rest on standard galactic-dynamics assumptions and cosmological parameters used to convert observed velocities into halo mass; no new particles or forces are introduced.

free parameters (1)
  • halo mass and concentration parameters
    Fitted during the rotation-curve decomposition to match the observed flat outer curve.
axioms (2)
  • standard math Newtonian gravity and circular-orbit assumption for interpreting the rotation curve
    Invoked to decompose the observed velocity field into baryonic and dark-matter contributions.
  • domain assumption Standard flat Lambda-CDM cosmology for converting observed quantities to M200
    Used to report the halo mass in units of solar masses.

pith-pipeline@v0.9.0 · 5685 in / 1502 out tokens · 66516 ms · 2026-05-10T18:07:53.568841+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

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

  1. The galaxy-halo connection and the dynamical evolution of a giant disc in a massive node of the Cosmic Web at z~3

    astro-ph.GA 2026-05 unverdicted novelty 5.0

    The Big Wheel at z~3 has a stellar-to-halo mass ratio of 0.06, higher than expected, implying efficient stellar assembly without major mergers or instabilities.

Reference graph

Works this paper leans on

2 extracted references · 1 canonical work pages · cited by 1 Pith paper

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    C., 2024, MNRAS, 532, 2965 Bacchini C., Fraternali F., Iorio G., Pezzulli G., 2019, A&A, 622, A64 Baldwin J

    Abdurro’uf et al., 2022, ApJS, 259, 35 AfruniA.,PezzulliG.,FraternaliF.,GrønnowA.,2023,MNRAS,524,2351 Allen N., et al., 2025, A&A, 698, A30 Angeloudi E., Falcón-Barroso J., Huertas-Company M., Boecker A., Sarmiento R., Eisert L., Pillepich A., 2024, Nature Astronomy, 8, 1310 Armillotta L., Fraternali F., Marinacci F., 2016, MNRAS, 462, 4157 Aung H., Mande...

    work page doi:10.1016/b978-0-443-21439-4.00109-7 2022

  2. [2]

    In Fig. A2, we compare the mass models obtained from fitting the fiducial circular-velocity profile (left panels) with those derived from the circular-velocity profiles computed separately for theapproachingandrecedingsidesofthegalaxyandforthecircular velocity approximated by the rotation velocity (see Sect. 4.3.1 and Fig. 7). This paper has been typeset ...

    2026