REVIEW 3 major objections 3 minor
No hidden monsters: Probing recently-quenched galaxies for obscured AGN with JWST-PRIMER MIRI and NIRCam
T0 review · 3 major / 3 minor · reviewed 2026-07-12 · grok-4.5
Pith's one-line read Massive recently-quenched galaxies show no mid-IR excess or hidden AGN above 1% Eddington
desk verdict Solid JWST mid-IR non-detection on massive PSBs; the <1% Eddington bound is useful but rests on unauditable template steps from the abstract alone. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
JWST/MIRI F770W and F1800W photometry combined with multi-band SED fitting and AGN/hot-dust template modelling that converts the absence of mid-IR excess into a quantitative upper bound on obscured accretion rate.
What would settle it
Deep mid-IR spectroscopy or higher-resolution MIRI imaging of the same massive PSBs that reveals either a clear AGN continuum/power-law or mid-IR luminosities requiring Eddington ratios above a few percent would overturn the claimed limit.
Extended reading notes
Core claim
Massive post-starburst galaxies (>10^10 M☉) at 1<z<2 exhibit no mid-infrared excess relative to the quiescent population; AGN template modelling therefore limits any dust-enshrouded AGN to Eddington ratios below 1 percent, so these systems show no excess AGN activity compared with older passive galaxies.
Load-bearing premise
The photometric post-starburst selection plus standard AGN and hot-dust templates correctly turn a non-detection of mid-IR excess into a firm upper limit on obscured black-hole growth, without missing heavily buried or non-standard SEDs.
Editorial extensions
If this is right
- Massive PSBs can be treated as free of significant ongoing obscured AGN activity once star formation has quenched.
- F770W–F1800W colour alone cleanly separates passive from star-forming systems at high stellar mass, offering a simple diagnostic for future surveys.
- Low-mass PSBs retain residual star formation that is visible at 18 μm, reinforcing a mass-dependent quenching pathway.
- Any AGN-driven quenching of massive galaxies must have finished before the post-starburst spectroscopic or photometric phase begins.
Reading between the lines
- If the mid-IR non-detection holds, models that require prolonged or delayed AGN feedback after quenching will need to operate below the 1 percent Eddington threshold or act only in shorter precursor phases.
- The clean F770W–F1800W passive locus may serve as a practical selection filter for large JWST or Roman samples when full SED fitting is impractical.
- A next test would be to stack the same massive PSBs in X-ray or radio to check whether any Compton-thick or radio-mode AGN remain invisible even to MIRI.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports a JWST/MIRI (F770W, F1800W) plus NIRCam/HST study of 65 photometrically selected post-starburst galaxies (PSBs) at 1<z<2 in PRIMER-UDS. High-mass PSBs (>10^10 M_⊙) show no mid-IR excess relative to the quiescent population, while low-mass PSBs exhibit enhanced 18 μm emission attributed to residual star formation. AGN/hot-dust template modelling is used to convert the massive-PSB non-detection into an upper bound of <1% Eddington ratio on any dust-enshrouded AGN. The F770W–F1800W colour is additionally presented as an effective passive versus star-forming diagnostic, especially at high mass. The abstract frames these results as evidence for mass-dependent quenching pathways and against excess obscured AGN activity in massive PSBs relative to older passives.
Significance. If the non-detection and the quantitative Eddington-ratio bound survive scrutiny of selection purity, control matching, and template systematics, the work supplies a timely mid-IR constraint on the role of obscured AGN in quenching at cosmic noon and a practical MIRI colour diagnostic. The mass-dependent dichotomy (no excess in massive PSBs; residual SF in low-mass systems) would be a useful observational input to quenching models. Strengths claimed in the abstract—deep JWST mid-IR imaging, a defined PSB sample, and an explicit population comparison—are observationally valuable if the methods fully support them.
major comments (3)
- The central quantitative claim—that any dust-enshrouded AGN in massive PSBs is limited to Eddington ratios <1%—rests on AGN/hot-dust template modelling of the MIRI non-excess. From the abstract alone this conversion cannot be audited: template library, torus geometry/covering factor, bolometric corrections, mass-to-Eddington scaling, and the treatment of residual SF versus AGN are unspecified. Non-standard or Compton-thick SEDs, or SF/AGN mis-attribution, could loosen or invalidate the bound without contradicting a reported non-excess. This step is load-bearing and must be demonstrated with explicit assumptions, sensitivity tests, and alternative templates in the methods.
- Photometric PSB selection purity at 1<z<2 is load-bearing for both the non-excess result and the mass-dependent dichotomy. Contamination by dusty star-formers or older passives would bias the MIRI excess test and the comparison to the quiescent control. The manuscript needs a quantitative purity assessment (and, where possible, spectroscopic cross-checks) before the non-detection can be read as a firm constraint on obscured AGN in true PSBs.
- The claim of 'no excess infrared emission (consistent with the quiescent population)' and 'no evidence for excess AGN activity relative to older passive galaxies' requires a carefully mass- and redshift-matched control. Any residual mismatch in dust content, SFH, or selection function could mimic or mask an AGN mid-IR excess. The control construction and statistical comparison must be shown explicitly for the high-mass subsample that carries the main claim.
minor comments (3)
- The abstract would be strengthened by stating the high-mass versus low-mass sample sizes (N) that underlie the reported dichotomy.
- Clarify whether the <1% Eddington limit is a typical/population upper bound or applies object-by-object, and whether it is a hard 3σ-style limit or a modelling-dependent ceiling.
- The F770W–F1800W diagnostic claim is useful; a brief quantitative figure of merit (e.g. completeness/contamination relative to multi-band SED classification) would make the abstract claim more falsifiable.
Circularity Check
No circularity: observational non-detection paper; abstract-only review finds no self-definitional or fitted-as-prediction steps.
full rationale
This is an observational constraint paper using JWST-PRIMER MIRI/NIRCam photometry of photometrically selected PSBs. The central claim is a non-detection of mid-IR excess in massive PSBs relative to the quiescent population, converted via AGN template modelling into an Eddington-ratio upper bound (<1%). With only the abstract available, no equations, fitted parameters, self-citations, uniqueness theorems, or ansatzes can be audited for circular reduction. The result is not forced by construction from its inputs: non-excess is an empirical measurement against an external control sample, not a redefinition of the selection or a fitted quantity renamed as a prediction. Template modelling and photometric PSB selection introduce standard modelling assumptions (correctness risk, not circularity). No self-definitional loops, no fitted-input-called-prediction, no load-bearing self-citation chain, and no renaming of a known result as a derivation are present in the available text. Score 0 is the honest finding for an abstract-only observational paper whose claim is grounded in external imaging rather than internal redefinition.
Assumptions & free parameters
free parameters (2)
- AGN template normalization / Eddington-ratio scaling
- Stellar-mass threshold 10^10 M_⊙
assumptions (3)
- domain assumption Photometric selection correctly identifies recently quenched post-starburst galaxies at 1<z<2 without large contamination by dusty star-formers or older passives.
- domain assumption Standard AGN and star-formation SED templates adequately describe mid-IR emission so that non-detection of excess limits obscured AGN power.
- domain assumption Hot dust mid-IR excess is a reliable tracer of either residual star formation or dust-enshrouded AGN in this redshift and mass range.
Cite this review
Pith. "Pith review of No hidden monsters: Probing recently-quenched galaxies for obscured AGN with JWST-PRIMER MIRI and NIRCam." pith.science (2026). https://pith.science/paper/JWHIU53R
@misc{pith2026260620800,
author = {Pith},
title = {Pith review of: No hidden monsters: Probing recently-quenched galaxies for obscured AGN with JWST-PRIMER MIRI and NIRCam},
year = {2026},
howpublished = {\url{https://pith.science/paper/JWHIU53R}},
note = {Machine review of arXiv:2606.20800}
}
abstract
We investigate the role of obscured active galactic nuclei (AGN) in recently quenched post-starburst galaxies (PSBs), using a sample of 65 photometrically selected PSBs in the PRIMER-UDS field at $1 < z < 2$. Combining JWST/MIRI 7.7 $\mu$m and 18 $\mu$m (F770W and F1800W) imaging with eight NIRCam and three HST/ACS bands, we probe hot dust emission to test for hidden AGN or dust-enshrouded star formation. We find strong differences between the low- and high-mass PSBs. Most high-mass PSBs ($ > 10^{10}\textrm{M}_\odot$) show no excess infrared emission (consistent with the quiescent population), indicating little or no dust-obscured activity, while low-mass PSBs display enhanced emission at 18 $\mu$m, which we attribute to residual star formation. AGN template modelling indicates that the absence of mid-IR excess in massive PSBs limits any dust-enshrouded AGN to Eddington ratios of $ < 1\%$. In addition, we show that the F770W--F1800W colour alone is a highly effective diagnostic for separating passive and star-forming galaxies, particularly at high stellar masses. Overall, our results provide further evidence for distinct quenching pathways within the PSB population, and confirm that massive PSBs show no evidence for excess AGN activity relative to older passive galaxies.
Figures
Figures from the paper (4 more)
Reviewed July 12, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.