{"id":"e6d21ace-bcad-400a-90f8-924581e8b09a","arxiv_id":"2506.15178","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"A search for Type II supernovae in two post-starburst galaxy samples finds zero events, implying their star formation rates are below 0.8 solar masses per year at 95% confidence.","lead":"The authors found no Type II supernovae inside two samples of post-starburst galaxies, galaxies whose star formation ceased about a billion years ago. From this absence they set a 95% upper limit of 0.8 solar masses per year on any residual star formation, tighter than earlier radio limits.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Survey completeness and effective exposure time assumption not validated; the 0.8 M_sun/yr limit may be too strong if galaxies were not observed for the full 7-year baseline.","rationale":"The paper's central claim is the 95% upper limit on current SFR in PSGs of <0.8 M_sun/yr. The statistical binomial calculation for the upper limit on the SN fraction is standard, and the conversion via k=0.0070 M_sun^-1 and T=7 years yields a per-galaxy SFR limit of about 0.8-0.9 M_sun/yr, consistent with the quoted value. The main vulnerability is the implicit assumption that the ZTF BTS observed every galaxy in the samples for the entire 7-year baseline. The paper's citation of Fremling et al. (2020) supports completeness for transients that ZTF detects, but not continuous temporal monitoring of specific galaxies. Type II SNe are visible for only weeks; missing a galaxy during its SN's visibility window would cause a false zero detection, artificially lowering the SFR limit. The paper provides no control-time calculation, no galaxy positions, and no exposure-time analysis. This is a load-bearing issue because the limit scales linearly with 1/T_eff: if the effective exposure is 2 years, the limit rises to about 2.8 M_sun/yr, above the previous radio limit of 1.6 M_sun/yr, undercutting the paper's improvement. This is exactly the concern the reader flagged as the weakest assumption. We therefore agree with the reader's CONDITIONAL verdict: the claim is plausible but requires verification of the survey coverage before it can be accepted. A concrete test is to compute the actual ZTF exposure time per galaxy and recalculate the limit; if the recalculated limit remains below about 1 M_sun/yr, the claim is supported, otherwise it should be relaxed.","tokens_in":3566,"tokens_out":12235,"duration_ms":119583,"concrete_test":"For each galaxy in the Melnick & De Propris (2013) and Alatalo et al. (2016) samples, compute the effective ZTF exposure time T_i using the public ZTF observing schedule and footprint (e.g., via the ZTF forced-photometry server or the survey's public exposure archive). Sum the T_i and recompute the 95% upper limit on the per-galaxy SFR using S < 3/(k * sum_i T_i) or a more exact binomial treatment that accounts for each galaxy's own T_i. Compare the resulting limit to the quoted 0.8 M_sun/yr; if the exposure-time-weighted limit exceeds about 1.6 M_sun/yr, the central claim is not supported and the paper should be revised.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim (95% upper limit SFR < 0.8 M_sun/yr) depends on treating the Zwicky Transient Facility Bright Transient Survey as having observed every target galaxy for the full T=7 years. Section 2 cites BTS completeness to z=0.05 (Fremling et al. 2020, Fig. 4), but that completeness refers to spectroscopic classification of transients that are discovered, not to continuous temporal monitoring of any particular galaxy. ZTF has weather, cadence, and sky-footprint gaps, and a Type II supernova is visible for only a few weeks. If a galaxy is observed with a duty cycle of 50%, the effective time is 3.5 years, raising the SFR limit to about 1.6 M_sun/yr (comparable to the old radio limit of Nielsen et al. 2012); with 20% duty cycle the limit becomes about 4 M_sun/yr, which would no longer support the conclusion that star formation has completely ceased. The paper provides no control-time or visibility calculation, no list of galaxy positions, and no cross-match details, so the T=7 year baseline is an unsupported assumption that is load-bearing for the headline limit.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the absence of Type II supernovae in two samples of post-starburst galaxies (65 galaxies from Melnick & De Propris 2013 and 246 from Alatalo et al. 2016) using the Zwicky Transient Facility Bright Transient Survey over a nominal 7-year baseline. From the zero detections, the authors derive binomial 95% upper limits on the supernova fraction and then convert these into upper limits on the current star formation rate, quoting SFR < 0.8 M_sun/yr for the Melnick & De Propris sample and < 0.3 M_sun/yr for the Alatalo et al. sample. They conclude that star formation in these galaxies has completely ceased, consistent with earlier radio limits. The paper is a short RNAAS-style research note.","tokens_in":3783,"tokens_out":4528,"duration_ms":47276,"significance":"The method is conceptually attractive: a non-detection of core-collapse supernovae directly probes recent massive-star formation, complementing radio and emission-line limits. The zero-event counts and binomial upper limits are simple and would be credible if the survey completeness and exposure-time assumptions are valid. However, as written, the manuscript does not establish those assumptions, and the conversion from the binomial limit to the quoted SFR is not shown. If the missing technical steps are supplied and the assumptions are validated, the result would be a useful independent constraint on residual star formation in post-starburst galaxies. The paper also benefits from comparing to existing literature (Nielsen et al. 2012; Ma et al. 2025), which provides context, but the current presentation leaves the central quantitative claim unsupported.","major_comments":[{"comment":"The derivation from the binomial upper limits (0.04 and 0.01) to the quoted volumetric star formation rate densities (< 0.06 and < 0.02 M_sun yr^-1 Mpc^-3) and then to per-galaxy SFR limits (< 0.8 and < 0.3 M_sun yr^-1) is not shown. The text gives no galaxy stellar masses, no survey volume, no selection function, and no equation linking the supernova fraction to the SFR. Without these details, the headline numbers are not reproducible and the conclusion cannot be verified. This is a load-bearing gap because the abstract's central claim depends on this conversion.","section":"Section 3, binomial-to-SFR conversion"},{"comment":"The assumption that the ZTF Bright Transient Survey provides 7 years of complete monitoring for every galaxy in both samples is not justified. The cited completeness of BTS to z = 0.05 (Fremling et al. 2020, Fig. 4) refers to spectroscopic classification of discovered transients, not to continuous temporal coverage of any particular galaxy. The manuscript does not demonstrate that all galaxies in the Melnick & De Propris and Alatalo et al. samples lie at z < 0.05, nor does it provide the effective ZTF control time per galaxy. With realistic cadence gaps, the effective exposure is shorter than 7 years; for example, a 50% duty cycle would roughly double the quoted SFR limit to ~1.6 M_sun/yr, comparable to the radio limit, and a 20% duty cycle would raise it to ~4 M_sun/yr, which would no longer support the claim that star formation has completely ceased.","section":"Section 2, completeness and exposure time"},{"comment":"The formula 'SNuM(M0) = N / T * M_RSS * 1 / 0 * sum_i M_i^(RSSM+1)' is garbled and undefined. The quantity RSSM is not defined in the formula, the summation index and range are unclear, and the units printed immediately after the formula ('SN(100 yr^-1 (10^10 M_sun)^-1)') are mangled. As written, the expression cannot be checked or applied, so the two quoted SNuM upper limits (< 0.008 and < 0.0004) are unsupported. The authors should provide the correct equation, with all variables defined, or cite the exact numbered equation from Ma et al. (2025).","section":"Section 3, SNuM formula"},{"comment":"The statement that 'star formation in these objects has completely ceased' is stronger than the analysis justifies. A 95% upper limit of 0.8 M_sun/yr is an upper bound, not a measurement of zero star formation; it is consistent with low-level ongoing star formation. The manuscript also does not propagate systematic uncertainties in the IMF normalization, the assumed supernova rate per unit star formation, or the completeness corrections. The conclusion should be softened to state that the current star formation rate is constrained to be very low, unless additional evidence is provided to rule out values below the quoted limit.","section":"Section 3, conclusion"}],"minor_comments":[{"comment":"The sentence beginning 'respectively. which is in good agreement' has a lowercase 'which' after a period; it should be 'This is in good agreement' or similar.","section":"Section 3, text after the SFR limits"},{"comment":"The line 'SNuM(M0) =< 0.0004 Alatalo et al . 2016' contains a typographical error: it should read 'SNuM(M0) < 0.0004' to be consistent with the other limit.","section":"Section 3, SNuM upper limit formatting"},{"comment":"The constant k = 0.0070 M_sun^-1 in the equation after 'SNR_CC = k * SFH' is stated without derivation or citation; while the Salpeter IMF is mentioned, the reader cannot easily verify the normalization or the mass limits. A brief explanation or reference to a standard calculation would help.","section":"Section 3, IMF conversion factor"},{"comment":"The manuscript does not state the redshift distribution, stellar mass range, or volume spanned by the two samples. At minimum, the mean redshift and mean stellar mass should be reported, since these enter the volumetric rate conversion and the comparison with the Ma et al. (2025) rates.","section":"Section 2, sample properties"},{"comment":"The figure caption is incomplete in the manuscript text: it ends with 'Error bars from X. Ma et al. (2025) are omitted.' without a full sentence describing the plotted points and limits. The caption should be self-contained for the reader.","section":"Figure 1 caption"}],"recommendation":"major_revision","confidential_remarks":"This is a research note submitted to RNAAS, so the level of detail is intentionally brief. However, the missing exposure-time validation and the unreproducible SFR conversion are not merely presentation issues; they affect the validity of the central claim. If the authors can supply the galaxy redshift/coverage information and a clear derivation, the paper could become a useful contribution. I would not recommend rejection at this stage, but the revision must address the load-bearing points listed above."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This is a short RNAAS note with a zero-detection argument: no Type II SNe in 65 + 246 local post-starburst galaxies, giving a 95% upper limit on SFR of <0.8 and <0.3 M_sun/yr. The idea is sound, and the limit is genuinely tighter than the old radio stack limit of <1.6 from Nielsen et al. (2012). The paper deserves credit for using a fresh tracer and for putting a number on quiescence.\n\nWhat is new is narrow: applying the ZTF BTS completeness to these two PSG samples. The binomial limit itself is standard, and the result is only as good as the assumptions. My main concern is the effective exposure time. The paper uses T=7 years (the BTS duration) for every galaxy, but BTS is a rolling survey with weather, cadence, and footprint gaps. A Type II SN is bright for only weeks. If each galaxy is actually monitored with a duty cycle of 50%, the limit roughly doubles to ~1.6 M_sun/yr, which is the same as the old radio limit; at 20% it becomes ~4 M_sun/yr and the conclusion collapses. No visibility/control-time calculation is given, and no galaxy positions or cross-match details are shown. This is a load-bearing assumption, not a nitpick.\n\nThere are also transparency gaps. The SNuM formula in Section 3 is garbled and undefined; I could not reproduce how '<0.008' and '=<0.0004' were obtained. The steps from the binomial fraction to the volumetric SFR and the per-galaxy SFR are not shown. The samples are not demonstrated to lie entirely at z<0.05, where BTS completeness is claimed. Finally, 'completely ceased' is too strong for an upper limit of 0.8 M_sun/yr; it is low, but not zero.\n\nWere these fixed, the paper would be a useful addition to the quenching literature. As is, the central number is not yet trustworthy. For a research note, the omissions are too large. I would not reject the idea. I would send it to a referee who knows BTS completeness, and ask the authors to add a control-time estimate, show the conversion arithmetic, justify the redshift range, and soften the claim.","headline":"A sensible zero-detection SFR limit that is probably too strong because the assumed survey exposure time and the conversion details are not justified.","tokens_in":4327,"tokens_out":3599,"would_cite":false,"duration_ms":35191,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"No Type II supernovae appear in 311 nearby post-starburst galaxies over seven years, yielding a 95% upper limit of 0.8 solar masses per year on current star formation and the conclusion that star formation has stopped.","keywords":["post-starburst galaxies","Type II supernovae","star formation rates","galaxy quenching","supernova rates","green valley galaxies","null detection"],"falsifier":"A spectroscopically confirmed Type II supernova whose position and redshift match any galaxy in either of the two post-starburst samples, with an explosion date inside the seven-year survey window, would overturn the zero-detection result; recomputing the limit with the actual per-galaxy exposure time would test whether the 0.8 solar-mass-per-year bound is secure.","tokens_in":3350,"feed_emoji":"💥","tokens_out":15251,"duration_ms":139782,"temperature":0.7,"pith_summary":"Post-starburst galaxies are galaxies whose optical spectra are dominated by A-type stars, a sign that a recent burst of star formation was abruptly halted roughly a billion years ago. This paper asks whether any star formation is still happening in them, using Type II supernovae—explosions of stars heavier than about eight solar masses—as a tracer of star formation over the last 50 million years. The authors search the seven-year Zwicky Transient Facility Bright Transient Survey for supernovae inside the standard Petrosian radii of 311 nearby post-starburst galaxies and find none. From zero detections they derive a 95% confidence upper limit of $0.8\\,M_\\odot\\,{\\rm yr}^{-1}$ on the current star formation rate in the optically selected sample and $0.3\\,M_\\odot\\,{\\rm yr}^{-1}$ in the younger 'shocked' sample, concluding that star formation in these galaxies has completely ceased. This sharpens the earlier radio-based limit and matters because these galaxies often contain large gas reservoirs that, in principle, could still fuel star formation.","feed_headline":"Zero supernovae cap star formation at 0.8 solar masses per year","feed_subtitle":"A seven-year survey found no exploding massive stars in 311 galaxies, confirming their star formation has shut off.","key_machinery":"The central machinery is the Type II supernova rate used as a star-formation clock. Type II supernovae are the explosions of stars with initial masses greater than about $8\\,M_\\odot$, and they occur within roughly 50 million years of their formation, so their occurrence rate traces recent star formation. The paper counts supernovae inside each galaxy's Petrosian radius (the standard aperture defined by SDSS photometry) using the Bright Transient Survey, which spectroscopically classifies all transients and is complete for Type II supernovae to $z=0.05$. With zero events in $N$ galaxies over a $T=7$ year baseline, the binomial distribution supplies the 95% upper limit on the supernova fraction, and the conversion ${\\rm SN}_{\\rm CC}=k\\times{\\rm SFH}$, with $k=0.0070\\,M_\\odot^{-1}$ derived from the Salpeter mass function, turns that count into a star-formation-rate limit. A rate-size slope of $-0.25$ is adopted to express the same null result as a volumetric supernova rate.","core_discovery":"On the paper's own terms, the discovery is a null detection with teeth: in 65 galaxies from the optically selected sample and 246 galaxies from the younger shock-selected sample, no Type II supernova is found within the Petrosian radius over the seven-year survey, which is complete for these supernovae to $z<0.05$. Treating the counts with the binomial distribution gives a 95% upper limit to the supernova fraction of 0.04 and 0.01 for the two samples. Converting through the relation ${\\rm SN}_{\\rm CC}=k\\times{\\rm SFH}$ with $k=0.0070\\,M_\\odot^{-1}$ (from a Salpeter initial mass function) yields ${\\rm SFR}<0.8\\,M_\\odot\\,{\\rm yr}^{-1}$ and ${\\rm SFR}<0.3\\,M_\\odot\\,{\\rm yr}^{-1}$ respectively. The authors conclude that star formation in post-starburst galaxies has completely ceased, that the limits agree with the 1.4 GHz stacked upper limit of $1.6\\,M_\\odot\\,{\\rm yr}^{-1}$, and that any residual radio emission is more likely from weak active galactic nuclei than from ongoing star formation.","pith_inferences":["A natural extension the paper does not pursue is to stack all 311 galaxies together, which would push the combined zero-count limit lower and could distinguish 'fully quenched' from 'still forming stars at a rate of a few hundredths of a solar mass per year.'","Because Type II supernovae trace only stars above about eight solar masses, the result leaves open the possibility of very low-level star formation producing only low-mass stars; deep ultraviolet imaging or nebular-line stacking would test that separately.","The same method could be applied to other green-valley populations or to a time-resolved sample of post-starburst galaxies of different ages, mapping how quickly star formation shuts off after a burst."],"forward_implications":["The current star formation rate in the optically selected post-starburst sample is below $0.8\\,M_\\odot\\,{\\rm yr}^{-1}$ at 95% confidence, and below $0.3\\,M_\\odot\\,{\\rm yr}^{-1}$ in the younger shock-selected sample.","Despite the molecular gas reservoirs previously found in many post-starburst galaxies, these galaxies are not forming massive stars at an observable rate, so the gas is not being converted into stars in any simple way.","The new limits agree with and sharpen the earlier 1.4 GHz radio upper limit, ruling out star formation as the main source of the residual radio emission in favor of weak active galactic nuclei.","The upper limits are comparable to those for elliptical galaxies, placing post-starburst galaxies among the most quiescent galaxy populations at low redshift."],"supporting_citations":[{"why":"Supplies the Bright Transient Survey data and the completeness statement for Type II supernovae to $z=0.05$ that underlies the null detection.","marker":"C. Fremling et al. (2020)"},{"why":"Provides the optically selected post-starburst sample of 65 galaxies in which zero supernovae are found.","marker":"J. Melnick & R. De Propris (2013)"},{"why":"Provides the younger shock-selected sample of 246 post-starburst galaxies in which zero supernovae are found.","marker":"K. Alatalo et al. (2016)"},{"why":"Supplies the functional conversion between core-collapse supernova rate and star formation history, along with the volumetric rates of other Hubble types used for comparison.","marker":"X. Ma et al. (2025)"},{"why":"Provides the 1.4 GHz stacked upper limit of 1.6 solar masses per year against which the new supernova-based limit is compared.","marker":"D. M. Nielsen et al. (2012)"},{"why":"Supplies the rate-size slope adopted for converting the null supernova count to a volumetric supernova rate.","marker":"W. Li et al. (2011)"},{"why":"Provides the SDSS photometric system and Petrosian radii used to set the supernova search aperture.","marker":"D. G. York et al. (2000)"}],"fun_headline_variants":["No Type II supernovae in post-starbursts caps star formation at 0.8 solar masses/yr","Zero supernovae in 311 galaxies confirm post-starburst star formation shutoff","No supernovae in post-starbursts: star formation below 0.8 solar masses/yr","No supernovae in post-starbursts: star formation ceased"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The argument assumes the seven-year sky survey caught every exploding massive star in these galaxies; if some were missed because they were too faint, dust-hidden, outside the chosen aperture, or observed for less than seven years, the true star-formation limit would be weaker.","fun_headline_variants_meta":{"raw":{"variants":["No Type II supernovae in post-starbursts caps star formation at 0.8 solar masses/yr","Zero supernovae in 311 galaxies confirm post-starburst star formation shutoff","No supernovae in post-starbursts: star formation below 0.8 solar masses/yr","No supernovae in post-starbursts: star formation ceased"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001796,"raw_usage":{"total_tokens":7049,"prompt_tokens":893,"completion_tokens":6156,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":509,"completion_tokens_details":{"reasoning_tokens":6058}},"tokens_in":509,"tokens_out":6156,"duration_ms":42732,"temperature":1.0,"reasoning_tokens":6058,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T19:41:55.880163+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A spectroscopically confirmed Type II supernova whose position and redshift match any galaxy in either of the two post-starburst samples, with an explosion date inside the seven-year survey window, would overturn the zero-detection result; recomputing the limit with the actual per-galaxy exposure time would test whether the 0.8 solar-mass-per-year bound is secure.","supporting_citations":[{"cited_title":"2013, MNRAS, 431, 2034, doi: 10.1093/mnras/stt199","cited_arxiv_id":null,"evidence_quote":"Provides the optically selected post-starburst sample of 65 galaxies in which zero supernovae are found."}],"review_version":2}