{"id":"20bbeca7-394d-4bf8-9e7f-b86d3d7db91b","arxiv_id":"2504.19111","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Regularized maximum likelihood imaging reproduces all non-Keplerian features seen in CLEAN images of seven protoplanetary disks, supporting their physical reality as planet indicators.","lead":"Using a second, independent way of turning ALMA telescope signals into pictures, this paper re-imaged seven protoplanetary disks and found that the same wiggles in the gas motion appeared again. The agreement suggests these wiggles, possible signs of young planets, are real and not an artifact of the standard imaging method.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"For six of seven sources the CV hyperparameters were tuned on the NKF channel itself; only LkCa 15 tests channel independence, so the 'independent reproduction' of NKFs may be partly by construction.","rationale":"The reader's verdict is CONDITIONAL, and I agree. My review identifies the same weakest assumption but frames it as a potential circularity in hyperparameter selection. The LkCa 15 multi-channel CV (Section 3.2, Table 1) is a genuine strength and provides some evidence that hyperparameters are stable, and the public release of code and cubes is a plus. However, the paper's own workflow (Table 2) shows that for all seven sources the CV channel is a CLEAN-selected NKF channel, and the claim that this choice is immaterial for the other six sources is unsupported by per-source tests. This is the key load-bearing condition for the central claim of independent reproduction. A concrete counter-test — re-running CV on a non-NKF channel for one localized-kink source — would either confirm the robustness or show that the NKF reproduction depends on the tuning channel. I recommend keeping the CONDITIONAL verdict, with this test as a condition for full acceptance.","tokens_in":21465,"tokens_out":7043,"duration_ms":71413,"concrete_test":"For at least one of the six non-LkCa 15 sources (e.g., AA Tau), repeat the full workflow with CV performed on a 12CO channel that does not contain the NKF — e.g., the counterpart channel at the same velocity offset on the opposite side of the line center, or the channel at v=7.0 km/s — and apply the resulting hyperparameters to the full cube. Then compare the RML image at v=7.8 km/s (NKF channel) with the original RML image: measure the NKF significance (e.g., residual after subtracting an azimuthally symmetric disk model, or a matched-filter SNR in the kink region) under both hyperparameter sets. If the NKF survives with comparable significance, the reproduction is robust to CV channel choice; if it weakens or disappears, the central claim is undercut.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 3.2 (Table 2) shows that for each of the seven sources the hyperparameters were obtained by 10-fold CV on a single 12CO channel. For the five sources with localized NKFs, that channel was explicitly chosen as one where the NKF is visible in the fiducial CLEAN images ('we used one of the channels where the NKF is visible'); for the two large-arc sources a representative NKF channel was also selected. The claim that this choice is immaterial rests entirely on the LkCa 15 experiment (Table 1), in which five channels across three lines and two continuum states were tested. No analogous channel-independence test is presented for AA Tau, HD 135344B, J1604, J1615, J1842, or SY Cha — and Table 2 shows source-to-source hyperparameter variation, so the LkCa 15 result cannot be assumed to transfer. The central claim that RML images 'independently' reproduce the NKFs is therefore load-bearing on an extrapolation: for six sources, the RML images of the very channels where NKFs are asserted were produced with regularizers selected on those same channels. If the CV-optimal hyperparameters on a non-NKF channel had been different (e.g., stronger TSV that smooths the kink), the NKF might not persist in the RML image. The RML fit itself is not circular, but the hyperparameter selection is informed by the feature under test, weakening the claim of independence. A quantitative, blinded comparison is also absent, but the channel-selection issue is the more specific vulnerability.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents regularized maximum likelihood (RML) imaging of 12CO J=3-2, 13CO J=3-2, and CS J=7-6 ALMA observations of seven protoplanetary disks from the exoALMA large program, using the open-source MPoL package with entropy, sparsity, and total squared variation regularization. Hyperparameters are chosen via 10-fold random-cell cross-validation on a single representative 12CO channel per source, following a more extensive CV stability test on LkCa 15. The authors compare the RML image cubes to the fiducial CLEAN cubes and claim that the RML images independently reproduce all non-Keplerian features, as well as broadly reproducing emission surfaces and temperature profiles. They also discuss resolution and noise properties of RML images and release the cubes and imaging scripts publicly.","tokens_in":21788,"tokens_out":10234,"duration_ms":93065,"significance":"If the central claim holds, the paper provides an important methodological cross-check for the exoALMA planet-detection program: agreement between two independent imaging approaches strengthens confidence that NKFs are real. The work is a valuable extension of RML imaging to multi-channel spectral-line data cubes, and the CV stability study on LkCa 15 is a genuine methodological contribution. The public release of data products and scripts is also a credit to the authors. However, the strength of the 'independent reproduction' claim is currently limited by the channel-selection procedure and by the absence of quantitative feature-significance testing, so the paper's main conclusion is not yet fully supported.","major_comments":[{"comment":"The CV hyperparameters for each source were obtained from a single 12CO J=3-2 channel chosen because the NKF is visible in the fiducial CLEAN images (AA Tau v=7.9, HD 135344B v=6.6, J1604 v=4.5, J1615 v=3.7, J1842 v=5.1, LkCa 15 v=6.9, SY Cha v=3.6). The claim that this channel choice is immaterial rests entirely on the LkCa 15 experiment in Table 1, in which five channels across three lines and two continuum-subtraction states were tested. Table 2 shows that the CV-optimal hyperparameters vary between sources (e.g., lambda_TSV from 5e-5 to 5e-4), so the LkCa 15 result cannot be assumed to transfer to the other six sources. For those six sources, the RML image of the very channel where the NKF is asserted was produced with regularizers selected on that same channel. The RML fit is not directly circular, because CV scores predictive power on withheld visibilities rather than matching the NKF, but the hyperparameter selection is nonetheless conditioned on the feature under test. If a non-NKF channel had yielded different CV-optimal hyperparameters (e.g., stronger TSV that smooths the kink), the claimed independent reproduction could be an artifact of the tuning channel. Please extend the channel-independence test to at least one non-NKF channel per source, or perform a blinded version in which the tuning channel is chosen without reference to the CLEAN NKF location, and report whether the NKF persists.","section":"3.2 (Table 2)"},{"comment":"The central claim that RML images 'independently and consistently reproduce' all NKFs is supported only by side-by-side visual inspection. There is no quantitative metric for feature presence or significance: no SNR of the kink in the RML image, no residual after subtracting a Keplerian model, no cross-correlation or mask-overlap statistic between CLEAN and RML feature maps, and no noise model for the RML images. The discussion in Section 5.1 shows that sparsity regularization suppresses background RMS by nearly two orders of magnitude (0.043 vs 3.953 mJy/beam in Figure 11) and that this suppression is spatially non-uniform, so visual agreement alone is not a sufficient statistical basis for the conclusion that 'the agreement between the two sets of independently synthesized image products suggests that these features are real' (Section 6). In addition, the sample was pre-selected because CLEAN showed NKFs, so the test is not blind. I recommend adding a quantitative feature-comparison metric, a null test (e.g., RML imaging of a source without NKFs or an injection-recovery of synthetic kinks), and explicit noise/uncertainty estimates before drawing the conclusion about the reality of the features.","section":"4 (Figures 2-9) and 6"}],"minor_comments":[{"comment":"The caption contains a typo: 'Botton' should be 'Bottom'.","section":"Table 1"},{"comment":"The text contains two typos: 'shame characteristic tapered power-law shape' should read 'same characteristic tapered power-law shape', and 'difference difference' should read 'difference'.","section":"5.2"},{"comment":"Section 5.1 refers to 'the native RML image of J1824', but the source in Figure 10 and the rest of the text is J1842. Also, the beam sizes listed as '0.5, 0.15, and 0.30' in Section 5.2 are presumably '0.05, 0.15, and 0.30'.","section":"5.1/5.2"},{"comment":"Several companion papers are cited as 'ApJL, TBD' (Teague et al. 2025; Loomis et al. 2025; Galloway-Sprietsma et al. 2025; Pinte et al. 2025). Since the manuscript's conclusions rely on Pinte et al. (2025) for the interpretation of the NKFs, the final version should include updated citations or clearly state their status.","section":"References"},{"comment":"The RML emission surfaces extend up to ~200 au further and the RML temperatures are systematically ~5 K lower (up to 13 K) than the CLEAN-based values. The paper leaves the cause unresolved; please either provide a quantitative explanation or explicitly flag this as a limitation in the conclusions, since the second conclusion bullet currently states these profiles are reproduced.","section":"5.2"}],"recommendation":"major_revision","confidential_remarks":"The paper is a useful contribution and the authors are careful in many ways, but the headline claim of independent verification needs strengthening. I recommend requiring the channel-independence test on additional sources and a quantitative feature metric before final acceptance. Also, since several key companion papers are cited as 'TBD', please confirm in the cover letter that they are available to the editor."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThe paper does what it sets out to do: RML images from MPoL reproduce the non-Keplerian features seen in the CLEAN images of all seven exoALMA disks. That is a useful result for the program, and it is the first systematic multi-channel RML application to disk gas. The more novel finding is that CV-chosen hyperparameters transfer across channels, molecular lines, and continuum-subtraction states, at least where tested. That is practically important because full-cube CV would be computationally prohibitive.\n\nWhere the paper is soft: the 'independent verification' language is a bit strong. For six of the seven sources, the hyperparameters were tuned by CV on a channel where the NKF is visible in the CLEAN images. The authors argue the choice of channel should not matter, and they demonstrate that on LkCa 15, but not on the other sources. So the reproduction of the NKF is not strictly independent of the feature under test. It is not circular in the narrow sense – the image is a direct fit to visibilities, and the CLEAN image only enters through total-flux normalization and source/channel selection – but the hyperparameters are informed by the very kink they are used to verify. That is a legitimate caveat.\n\nSecond, all comparisons are visual. There is no quantitative significance estimate for the NKFs in the RML images, and the noise statistics are complicated by sparsity regularization, which suppresses background to near zero. A simple injection-recovery test or a residual-based detection metric on a couple of sources would have strengthened the central verification claim considerably.\n\nThe emission-surface and temperature comparisons are a genuine addition, and the authors handle the known offsets honestly. Releasing the full cubes and scripts is exactly right.\n\nWho should read this: anyone using NKFs as planet indicators in ALMA data, and anyone who wants a workable CV protocol for RML cubes. The paper deserves peer review. In review, I would ask for either a channel-independence test on one or two more sources or a rewording of the 'independent reproduction' conclusion to reflect that hyperparameters were chosen on representative channels, with only LkCa 15 directly testing channel invariance.","headline":"A credible RML verification of CLEAN-detected non-Keplerian features, though the hyperparameter tuning is partly informed by the features under test and the comparison is visual.","tokens_in":22495,"tokens_out":3593,"would_cite":true,"duration_ms":35048,"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":"Re-imaging seven exoALMA disks with regularized maximum likelihood reproduces every non-Keplerian feature seen in CLEAN images, suggesting the features are real and strengthening the case that some reveal young planets.","keywords":["protoplanetary disks","non-Keplerian features","regularized maximum likelihood imaging","ALMA","image reconstruction","cross-validation hyperparameters","disk kinematics","planet signatures"],"falsifier":"Run the same 10-fold random-cell cross-validation independently on every velocity channel of the LkCa 15 12CO J=3-2 cube, including at least one channel far from the non-Keplerian feature (e.g., v = 4.8 km/s), and compare the optimal $(\\lambda_{\\rm ent}, \\lambda_{\\rm TSV}, \\lambda_{\\rm spa})$ values channel by channel. If the non-Keplerian feature appears or disappears in images made with channel-by-channel tuning compared with the single-channel-tuned settings, the transferability claim fails.","tokens_in":21298,"feed_emoji":"🔭","tokens_out":10941,"duration_ms":94656,"temperature":0.7,"pith_summary":"This paper asks whether the faint kinks and twists seen in the standard CLEAN images of seven exoALMA protoplanetary disks — the so-called non-Keplerian features, or NKFs — would survive a completely different imaging method. It re-images the same calibrated ALMA visibility data with regularized maximum likelihood (RML), which solves pixel-by-pixel for the image that best fits the data while paying penalties for smoothness, sparsity, and entropy. In all seven disks, the RML images independently reproduce every NKF seen in CLEAN, including compact planet-like kinks in AA Tau, J1615, J1842, LkCa 15, and SY Cha and large-scale arcs in HD 135344B and J1604. Using LkCa 15 as the test case, the paper also finds that hyperparameters chosen by cross-validation on a single representative velocity channel carry over to all channels of all three molecular lines and to both continuum-subtracted and non-continuum-subtracted data. If these results hold, the exoALMA features are not artifacts of one algorithm, and multi-channel RML imaging becomes practical for large surveys.","feed_headline":"Second imaging method confirms seven disks' non-Keplerian features","feed_subtitle":"The RML maps match CLEAN maps, boosting confidence these kinks are real disk flows, not artifacts.","key_machinery":"The load-bearing mechanism is the RML loss function, $L(I) = L_{\\rm nll}(I) + \\lambda_{\\rm ent} L_{\\rm ent}(I) + \\lambda_{\\rm spa} L_{\\rm spa}(I) + \\lambda_{\\rm TSV} L_{\\rm TSV}(I)$, where $L_{\\rm nll}$ is the negative log likelihood (half the chi-squared between model and gridded visibilities), $L_{\\rm ent}$ is a maximum-entropy term that keeps pixels positive and uniform, $L_{\\rm spa}$ is an L1 sparsity penalty that drives faint background pixels to zero, and $L_{\\rm TSV}$ is total squared variation that favors piecewise-smooth structure. The hyperparameters $\\lambda_{\\rm ent}$, $\\lambda_{\\rm spa}$, and $\\lambda_{\\rm TSV}$ are set by 10-fold random-cell cross-validation: the gridded visibility cells are split into training and testing sets, the image is fit to the training cells, and the predictive score on the withheld cells selects the best values. The paper's practical result is that this tuning needs to happen only once per source, on one representative velocity channel, and the same settings then produce the full image cube for every molecular line and continuum-subtraction state.","core_discovery":"The central claim is that regularized maximum likelihood (RML) imaging, applied to the same calibrated ALMA visibilities, independently and consistently reproduces the non-Keplerian features that appear in the fiducial CLEAN images of all seven disks studied, and that this agreement is evidence the features are real rather than products of a specific deconvolution procedure. The compact kink-like NKFs in AA Tau, J1615, J1842, LkCa 15, and SY Cha, and the large-scale arcs in HD 135344B and J1604, are recovered in the 12CO J=3-2 RML cubes across multiple adjacent channels. The RML cubes also agree with CLEAN on general emission morphology in 13CO J=3-2 and CS J=7-6, while differing in detail: sparsity regularization suppresses background noise by nearly two orders of magnitude, RML emission surfaces extend further in radius (sometimes by more than 200 au), and brightness temperatures come out systematically lower by roughly 5 K. The paper presents this agreement as a strengthening of the planet-related interpretations of these features made elsewhere in the exoALMA program.","pith_inferences":["A direct test of the paper's transferability claim would be to run the same cross-validation on every channel of one full LkCa 15 cube; if optimal hyperparameters shift enough to change feature morphology, single-channel tuning would need qualification.","Because sparsity regularization suppresses background noise far below the thermal noise floor, significance estimates computed from RML images should use a regularization-aware noise model rather than the standard CLEAN-style blank-region RMS.","The same regularization machinery could be pointed in reverse: super-resolved RML imaging of disks without obvious NKFs might expose kinematic perturbations too faint for CLEAN, a search the paper itself lists as future work.","If RML and CLEAN systematically agree on morphology but disagree on absolute temperature, then disk temperature measurements should carry an imaging-systematic term that simulations with known temperature fields could calibrate."],"forward_implications":["The non-Keplerian features in all seven disks can be treated as real kinematic structure rather than deconvolution artifacts, which strengthens the planet-mass and location constraints derived from them in the companion analysis.","RML image cubes become a practical cross-check for ALMA disk surveys: one cross-validation run per source is enough to synthesize a full cube, so the computational cost no longer scales with the number of velocity channels.","Emission surfaces and temperature profiles measured from RML cubes reach larger radii and lower noise than CLEAN, but the systematic roughly 5 K temperature offset means absolute disk temperatures are imaging-dependent and should not be mixed across products without calibration.","For high-sensitivity ALMA data with good $(u,v)$ coverage, a combination of TSV and sparsity regularization (entropy often set to zero) is a reliable default configuration for similar imaging programs."],"supporting_citations":[{"why":"Supplies the planet-mass interpretation of the non-Keplerian features that this paper's RML agreement is meant to corroborate.","marker":"Pinte et al. 2025"},{"why":"Establishes the RML workflow and random-cell cross-validation procedure that this paper extends to multi-channel cubes.","marker":"Zawadzki et al. 2023"},{"why":"Introduces the total squared variation regularizer used in the loss function.","marker":"Kuramochi et al. 2018"},{"why":"Documents the calibration and CLEAN imaging that produced the fiducial images against which the RML images are compared.","marker":"Loomis et al. 2025"},{"why":"Defines the exoALMA sample and the non-Keplerian feature search that motivates this study.","marker":"Teague et al. 2025"},{"why":"Demonstrated practical RML imaging on ALMA protoplanetary disk data, establishing the viability of the method for this data type.","marker":"Cárcamo et al. 2018"},{"why":"Recommends using multiple image synthesis techniques for kinematic planet detection, the principle this paper executes.","marker":"Disk Dynamics Collaboration et al. 2020"}],"fun_headline_variants":["RML imaging independently reproduces seven disks' non-Keplerian features","CLEAN and RML agree: seven disks show real non-Keplerian flows","Independent RML maps confirm non-Keplerian features in seven disks","RML verification boosts confidence in compact kinks and large arcs","Seven disks' non-Keplerian features survive independent imaging method"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that cross-validation on a single representative velocity channel per source — chosen by eye and often containing the non-Keplerian feature — yields hyperparameters that are valid for every other channel, molecular line, and continuum-subtraction state, a generalization tested thoroughly only on LkCa 15.","fun_headline_variants_meta":{"raw":{"variants":["RML imaging independently reproduces seven disks' non-Keplerian features","CLEAN and RML agree: seven disks show real non-Keplerian flows","Independent RML maps confirm non-Keplerian features in seven disks","RML verification boosts confidence in compact kinks and large arcs","Seven disks' non-Keplerian features survive independent imaging method"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000312,"raw_usage":{"total_tokens":1857,"prompt_tokens":1106,"completion_tokens":751,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":722,"completion_tokens_details":{"reasoning_tokens":653}},"tokens_in":722,"tokens_out":751,"duration_ms":6356,"temperature":1.0,"reasoning_tokens":653,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T06:00:52.372777+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same 10-fold random-cell cross-validation independently on every velocity channel of the LkCa 15 12CO J=3-2 cube, including at least one channel far from the non-Keplerian feature (e.g., v = 4.8 km/s), and compare the optimal $(\\lambda_{\\rm ent}, \\lambda_{\\rm TSV}, \\lambda_{\\rm spa})$ values channel by channel. If the non-Keplerian feature appears or disappears in images made with channel-by-channel tuning compared with the single-channel-tuned settings, the transferability claim fails.","supporting_citations":[{"cited_title":"2025, , TBD","cited_arxiv_id":null,"evidence_quote":"Supplies the planet-mass interpretation of the non-Keplerian features that this paper's RML agreement is meant to corroborate."},{"cited_title":"Benisty , M","cited_arxiv_id":null,"evidence_quote":"Documents the calibration and CLEAN imaging that produced the fiducial images against which the RML images are compared."}],"review_version":1}