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arxiv: 2606.30763 · v1 · pith:WBQGQ5MFnew · submitted 2026-06-29 · 🌌 astro-ph.GA · astro-ph.IM

A SHARP Look at Quenching and Bulge-Disk Growth in Massive Galaxies at Cosmic Noon

Chiara Mancini , Adriana Gargiulo , Alvio Renzini , Emanuele Daddi , Stefano Zibetti , Fabio R. Ditrani , Anna R. Gallazzi , Susanna Bisogni
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Paolo Franzetti Giustina Vietri Louis Gabarra Fabrizio Gentile Marcella Longhetti Marco Scodeggio
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Pith reviewed 2026-07-01 02:04 UTC · model grok-4.3

classification 🌌 astro-ph.GA astro-ph.IM
keywords galaxy quenchingbulge-disk decompositionintegral field spectroscopycosmic noonmassive galaxiesstar formation historiesionized gasfeedback outflows
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The pith

The SHARP-VESPER IFS will enable the first simultaneous bulge-disk decomposition of stellar populations plus spatially resolved ionised gas mapping in massive galaxies at 2.2<z<3.5.

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

The paper argues that the physical link between bulge growth and the shutdown of star formation in massive galaxies remains unclear because existing data lack the resolution and sensitivity to separate components at cosmic noon. The SHARP-VESPER Integral-Field Spectrograph is presented as the tool that can close this gap through its combination of ELT sensitivity, 31-mas resolution, and 12-IFU multiplexing. With 15-hour exposures the instrument is expected to deliver sufficient signal-to-noise to extract independent star-formation histories, ages, metallicities, and alpha-enhancements for bulges and disks while mapping nebular lines and outflows on sub-kpc scales. These measurements would directly compare the timing of structural change and star-formation suppression, testing inside-out quenching and distinguishing fast versus slow pathways.

Core claim

The SHARP-VESPER IFS can, for the first time, combine bulge-disk decomposition of stellar populations with spatially resolved mapping of ionised gas in galaxies above 10^11 solar masses at redshifts 2.2 to 3.5. Typical 15-hour exposures are projected to reach S/N>15-20 on the continuum of inner bulges and outer disks and S/N>5 on [OII], H-beta, [OIII], and H-alpha lines on sub-kpc scales. The resulting data will reconstruct component-specific star-formation histories, ages, metallicities, and alpha-enhancements while tracing star formation, gas kinematics, and feedback-driven outflows, thereby testing whether quenching proceeds inside-out and linking structural transformation to feedback pro

What carries the argument

The SHARP-VESPER Integral-Field Spectrograph, which combines ELT-class sensitivity, 31-mas spatial resolution, broad near-IR wavelength coverage, and 12-IFU multiplexing to perform simultaneous stellar-population and gas analyses.

If this is right

  • Independent bulge and disk star-formation histories will reveal the relative timing of bulge assembly and star-formation suppression.
  • Spatially resolved gas kinematics and outflow maps will connect feedback processes to the structural transformation.
  • Component-specific ages and metallicities will distinguish fast and slow quenching pathways.
  • Comparison of inner versus outer regions will test whether quenching proceeds inside-out.
  • The programme targets systems on the main sequence shortly before quenching or already in the green valley.

Where Pith is reading between the lines

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

  • These resolved histories could supply direct timing constraints for AGN-feedback models that currently rely on integrated properties.
  • Efficient multiplexing would allow statistical samples of rare high-mass systems to be assembled in reasonable observing time.
  • The same data set could be cross-matched with lower-redshift integral-field surveys to trace the full evolutionary sequence of bulge growth and quenching.
  • If inside-out signatures are confirmed, models of disk instability and merger-driven bulge formation would need to incorporate differential quenching timescales across galaxy components.

Load-bearing premise

The assumption that 15-hour exposures will achieve the stated signal-to-noise ratios on both continuum and nebular lines rests on the instrument attaining its design sensitivity and resolution.

What would settle it

Direct measurement of delivered signal-to-noise ratios on real targets showing values below 15-20 per spectral resolution element on the continuum or below 5 on the nebular lines would falsify the feasibility claim for the planned decomposition and mapping.

Figures

Figures reproduced from arXiv: 2606.30763 by Adriana Gargiulo, Alvio Renzini, Anna R. Gallazzi, Chiara Mancini, Emanuele Daddi, Fabio R. Ditrani, Fabrizio Gentile, Giustina Vietri, Louis Gabarra, Marcella Longhetti, Marco Scodeggio, Paolo Franzetti, Stefano Zibetti, Susanna Bisogni.

Figure 1
Figure 1. Figure 1: Top: Position of our target galaxies at 2.2 < 𝑧phot < 3.5 on the 𝑀∗–SFR plane, compared to the star-forming MS, and its 2.5𝜎 scatter, from Schreiber et al. (2015) at the median redshift 𝑧 ∼ 2.5 (black solid and dashed lines). Grey filled circles show galaxies from the COSMOS-Web parent catalogue in the same redshift range. Our targets (black-edged circles, colour-coded by Sérsic index) comprise the brighte… view at source ↗
read the original abstract

The physical mechanisms that quench star formation in massive galaxies remain poorly understood. At cosmic noon (1<z<3), when star formation and AGN activity peak, galaxies rapidly evolve from star-forming disks into quiescent, bulge-dominated systems. While quenching correlates with stellar mass and bulge growth, the causal link between bulge assembly, star-formation suppression, and feedback processes remains unclear. Stellar population analysis from spatially resolved spectroscopy of galaxies caught during quenching is crucial to advance on this issue. We show that the SHARP-VESPER Integral-Field Spectrograph (IFS) can efficiently fill this gap by combining ELT-class sensitivity, 31 mas spatial resolution (>3x sharper than JWST) and broad near-IR wavelength coverage with 12-IFU multiplexing. This will enable, for the first time, a simultaneous bulge-disk decomposition of stellar populations and spatially resolved mapping of ionised gas in massive galaxies (log $M_*/M_{\odot}\geq 11$) at 2.2<z<3.5, targeting systems on the main sequence shortly before quenching or already in the green valley. With typical exposure times of 15 hr, we will obtain S/N>15-20 per spectral resolution element, on the inner bulge, and outer disk extracted spectral continuum, and S/N>5 for nebular lines ([OII], H$\beta$, [OIII], H$\alpha$) on sub-kpc scales. These observations will allow us to reconstruct independent bulge and disk star-formation histories, ages, metallicities, and $\alpha$-enhancements, while mapping spatially resolved star formation, gas kinematics, and feedback-driven outflows. By directly comparing the timing of bulge growth and star-formation suppression across galaxy components, this programme will test whether quenching proceeds inside-out, distinguish fast and slow quenching pathways, and link structural transformation to feedback processes in the most massive galaxies at cosmic noon.

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

1 major / 2 minor

Summary. The manuscript is an observing proposal for the SHARP-VESPER Integral-Field Spectrograph on the ELT. It claims that 15 hr exposures on massive galaxies (log M*/M⊙ ≥11) at 2.2<z<3.5 will deliver S/N>15-20 per spectral resolution element on bulge and disk continuum and S/N>5 on nebular lines, enabling the first simultaneous bulge-disk decomposition of stellar populations together with spatially resolved ionised-gas mapping to test inside-out quenching, distinguish fast/slow pathways, and link structural change to feedback.

Significance. If the instrument meets its stated design specifications for 31 mas resolution and sensitivity, the program would supply component-resolved star-formation histories, ages, metallicities, and gas kinematics for the transition population at cosmic noon, a capability not currently available and directly relevant to the open question of how bulge growth and star-formation suppression are causally connected.

major comments (1)
  1. [Abstract] Abstract: the claim that 15 hr exposures will achieve S/N>15-20 on the extracted bulge and disk continuum and S/N>5 on [OII], Hβ, [OIII], Hα is load-bearing for the entire science case yet is presented without any exposure-time calculation, sensitivity model, or reference to instrument performance data; this assumption is explicitly flagged in the proposal but remains unsubstantiated.
minor comments (2)
  1. The abstract defines cosmic noon as 1<z<3 but targets 2.2<z<3.5; a brief clarification of the adopted range would remove the minor inconsistency.
  2. The proposal would be strengthened by explicit citation of existing JWST IFS or ground-based studies of quenching at similar redshifts to quantify the unique gain from the proposed resolution and multiplexing.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their constructive review and positive evaluation of the scientific significance. We address the major comment below and will revise the manuscript to incorporate the requested substantiation.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the claim that 15 hr exposures will achieve S/N>15-20 on the extracted bulge and disk continuum and S/N>5 on [OII], Hβ, [OIII], Hα is load-bearing for the entire science case yet is presented without any exposure-time calculation, sensitivity model, or reference to instrument performance data; this assumption is explicitly flagged in the proposal but remains unsubstantiated.

    Authors: We agree that the S/N performance claims require explicit support. Although the proposal text flags the numbers as assumptions pending detailed modeling, the revised manuscript will add a dedicated methods subsection (or appendix) presenting the exposure-time calculations, the adopted sensitivity model for SHARP-VESPER, references to the instrument's 31 mas resolution and throughput specifications, and the resulting per-component S/N estimates for continuum and nebular lines. This will make the feasibility case fully transparent without altering the core science goals. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

The document is an observing proposal for future SHARP-VESPER IFS observations on the ELT. It contains no equations, derivations, parameter fitting, or data analysis. All statements are prospective claims about achievable S/N and science return conditional on instrument performance meeting design specs. No load-bearing step reduces a result to its own inputs by construction, self-citation, or renaming. The feasibility assumption is explicitly flagged as external and is not internally derived.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The proposal relies on standard domain assumptions from extragalactic astronomy and instrument performance claims; no free parameters, new axioms beyond those, or invented entities are introduced in the abstract.

axioms (2)
  • domain assumption Stellar population synthesis models can reliably extract ages, metallicities, alpha-enhancements, and star-formation histories from the extracted spectra.
    Invoked when stating that observations will allow reconstruction of independent bulge and disk star-formation histories.
  • ad hoc to paper The SHARP-VESPER instrument will deliver the stated 31 mas spatial resolution, sensitivity, and multiplexing as per its design specifications.
    Central to the feasibility and S/N claims in the abstract.

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