{"id":"3ac6fe89-5851-4ee8-ad95-5d0ae83f8554","arxiv_id":"2506.20448","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":4,"one_line_summary":"ALMA CO(1-0), CO(2-1), and CO(3-2) maps of PKS 0023-26 reveal extreme molecular line ratios and gas depletion around the radio lobes, showing how jet feedback changes as the radio source grows.","lead":"New ALMA observations of the young radio galaxy PKS 0023-26 map three carbon monoxide transitions, showing that the radio jet's impact on cold gas shows up most clearly in molecular line ratios and gas distribution, not in gas motion. The data provide a concrete case of an active galactic nucleus affecting its host galaxy's fuel supply over several kiloparsecs.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Outer high-R32 region is not uniquely attributable to the jet cocoon; merger-induced turbulence is an equally viable alternative that the paper's own data cannot exclude.","rationale":"The reader's weakest_assumption identifies exactly this degeneracy, and the paper itself flags it and proposes the same control. The observational core—CO(1-0) non-detection at the core, R32 ~ 1 between the core and N lobe, gas wrapped around the lobe—is robust and well supported. I considered whether the luminous optical AGN could also explain the central line-ratio anomalies via radiation/X-ray heating, but the paper already discusses this possibility, and the reader's concern about the outer region is more load-bearing because it undercuts the largest-scale, most novel claim. No additional internal inconsistency was found. Therefore the CONDITIONAL verdict stands unchanged.","tokens_in":23029,"tokens_out":14183,"duration_ms":148888,"concrete_test":"Run a control ALMA program: observe 3–5 non-AGN major mergers at z≈0.3 with comparable stellar mass, gas fraction, and interaction stage in CO(1-0), CO(2-1), and CO(3-2) at matched resolution (~2 kpc), analyzed with the same pipeline. If R32 > 0.6 extends more than ~2 kpc from the nucleus in these non-AGN mergers, the cocoon interpretation for PKS 0023–26 is not unique and the paper's central interpretation must be revised to allow a dominant merger contribution.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's central physical inference—that the extended region of high CO excitation (R32 > 0.6) reaching ~2–5 kpc beyond the N lobe and perpendicular to the radio axis is produced by the expanding jet cocoon—depends on the assumption that the ongoing galaxy merger does not dominate the excitation there. The manuscript itself concedes this in Sect. 4.1: turbulence and dissipation as accreted gas settles 'might explain the region of enhanced excitation beyond the N lobe,' and the Conclusions describe that same region as 'difficult to reconcile' with the cocoon picture. The supporting evidence is spatial coincidence with the radio axis, but in a galaxy whose gas distribution is strongly asymmetric and unsettled due to the merger, this coincidence is not decisive. If merger-induced turbulence alone yields R32 > 0.6 over several kpc, then the multi-kpc cocoon claim—the most novel part of the paper—falls, even though the central kpc line-ratio anomalies and the gas depletion around the N lobe remain valid. The concern is causal attribution, not data quality.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents new ALMA CO(1-0) and CO(3-2) observations of the young radio galaxy PKS 0023−26 (z=0.32188), combined with the existing CO(2-1) data of Morganti et al. (2021). The data are matched in resolution and velocity binning, absorption is removed from the CO(1-0) cube via clean components, and the same source mask derived from the highest-S/N transition is applied to all three transitions to avoid S/N-dependent biases in line ratios. The main observational results are: (1) CO(1-0) is not detected at the radio core while CO(2-1) and CO(3-2) are bright there, implying R21 ≳ 1.9 in the central beam; (2) the CO(3-2) emission shows a broad central profile (FWZI ~600 km/s) and high velocity dispersion between the core and the northern lobe; (3) molecular gas is depleted at the northern lobe and appears wrapped around it; and (4) the R32 = I(3-2)/I(2-1) ratio peaks near 1.0–1.2 between the core and the N lobe and remains above 0.6 over a region extending up to ~5 kpc from the source, including an extension beyond the N lobe. The authors interpret the inner region as an AGN-driven outflow and the outer high-ratio gas as evidence of a jet cocoon inducing turbulence and enhanced excitation, while explicitly acknowledging that turbulence from the ongoing galaxy merger is a viable alternative for part of the outer region.","tokens_in":23197,"tokens_out":9782,"duration_ms":109040,"significance":"If the interpretation holds, the paper is a valuable demonstration that AGN feedback can be traced through molecular excitation and gas distribution, not only kinematics, on scales from the central kiloparsec to several kiloparsec, and that different feedback modes (ejective and preventative) can coexist in one source. The observational work is careful: the use of a common mask derived from the highest-S/N transition, the removal of absorption before imaging, and the quoting of extreme ratios against 3-sigma upper limits are all sound practices. The line ratios are measured rather than fitted, and the energetic estimates are explicitly parameterized with literature conversion factors and stated geometric assumptions. The paper also openly identifies the main degeneracy—merger-induced turbulence versus jet-cocoon excitation—and calls for non-AGN merger control observations. The central-kpc line-ratio anomalies and the gas depletion around the N lobe are robust; the multi-kpc cocoon interpretation is plausible but not uniquely established.","major_comments":[{"comment":"The most novel interpretation—that the extended R32 > 0.6 region reaching ~2–5 kpc beyond the N lobe and perpendicular to the radio axis is produced by the expanding jet cocoon—is not uniquely supported. The manuscript itself states in §4.1 that turbulence from accreted gas settling in the merger 'might explain the region of enhanced excitation beyond the N lobe' and in §5 that this region is 'difficult to reconcile' with the cocoon picture. Because the galaxy is demonstrably interacting (tidal tails, companions at similar redshift), spatial coincidence with the radio axis is not a decisive discriminator. If merger-driven turbulence alone produces R32 > 0.6 over several kpc, the multi-kpc cocoon claim falls, although the central-kpc anomalies and N-lobe depletion remain valid. Please either provide a quantitative test separating the mechanisms (e.g., comparison with tidal-tail morphology, modeling of merger-driven excitation, or a non-AGN merger control sample) or consistently downgrade the abstract and §3.3 to present the cocoon as one of several viable explanations.","section":"§4.1, §5, Fig. 8"},{"comment":"The R32 map is presented without an uncertainty map or an explicit significance threshold. The statements that R32 reaches 1.0–1.2 between the core and the N lobe and that R32 > 0.6 extends several kpc require a quantitative definition of which pixels are considered detected in both transitions. Please add noise-based confidence contours, or state the S/N threshold used to construct the ratio map and to define the R32 > 0.6 region; without this, the spatial extent of the high-excitation region cannot be assessed.","section":"§3.3, Fig. 8"}],"minor_comments":[{"comment":"The notation 'R21 /greaterorsimilar1.9' should be typeset as R21 ≳ 1.9.","section":"§3.3"},{"comment":"The object 'IC 5053' appears to be a typo for 'IC 5063' (compare §4.1).","section":"§4.3"},{"comment":"The phrase 'in a ways that can go beyond' should read 'in ways that can go beyond'.","section":"§4.3"},{"comment":"The three transitions have different maximum recoverable scales (4.7, 3.8, and 2.5 arcsec for CO(1-0), CO(2-1), and CO(3-2)); please comment on whether the shorter maximum recoverable scale of the CO(3-2) data affects the line-ratio measurements in the outer low-surface-brightness regions, noting that any missing CO(3-2) flux would bias R32 low, not high.","section":"Table 1, §2"},{"comment":"The companion paper (Siemiginowska et al. 2026) is cited as providing X-ray evidence for enhanced hot gas at the N lobe and the R32 peak; since it is listed as submitted, the supporting X-ray interpretation should be marked as preliminary.","section":"§4.1, References"},{"comment":"The phrase 'the latterly expanding cocoon' is unusual; consider 'the laterally expanding cocoon'.","section":"§4.1"}],"recommendation":"major_revision","confidential_remarks":"The data handling is of high quality and the observational facts are likely to be correct. My main concern is interpretational: the multi-kpc cocoon claim is presented in the abstract and Section 3.3 with more confidence than the paper's own caveats allow. If the authors can provide a quantitative discriminator, this would be a strong paper; otherwise it should be reframed. I also note that the companion Chandra paper could materially affect the interpretation, so the refereeing schedules of the two papers should be coordinated if possible."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The observational core here is in good shape. The new ALMA CO(1-0) and CO(3-2) data, combined with the earlier CO(2-1) cube, give the first resolved three-transition line-ratio maps for PKS 0023-26. The masking strategy (using the highest-S/N cube for all transitions) and the subtraction of absorption via clean components are exactly the kind of care that keeps line ratios from being S/N artifacts. The CO(1-0) non-detection at the core, with a lower limit of R21 > 1.9, is a clean and striking result. The reported R32 values of 1.0-1.2 along the jet axis and the gas wrapping around the northern lobe are also convincing as measurements. This is reproducible observational evidence, and the paper does not overclaim the data itself.\n\nWhere I agree with the stress-test note: the novel physical interpretation—that the high-R32 region extending 2-5 kpc beyond the N lobe and perpendicular to the jet is caused by the expanding jet cocoon—is not uniquely forced by the data. The galaxy is clearly in an ongoing merger, with tidal tails and unsettled gas. The authors themselves say in Sect. 4.1 that turbulence from accreted gas settling 'might explain the region of enhanced excitation beyond the N lobe,' and the Conclusions describe that outer region as 'difficult to reconcile' with the cocoon picture. That is an honest concession, and it means the most interesting claim is conditional. But the paper does the right thing by spelling out a testable discriminator: line-ratio studies of non-AGN mergers. If those show similar high R32 values, the cocoon interpretation for the outer region falls; if not, it gains support. The central-kpc anomalies and the lobe depletion stand regardless.\n\nThe energetics section is standard and properly caveated; the conclusion that only a small fraction of jet energy is transferred to the ISM is not load-bearing for the main result. My only minor gripe is that the abstract slightly overstates the cocoon case relative to the body of the paper, but that is a fixable wording issue.\n\nThis is a single-object study, so the significance is incremental rather than transformative. But it is honest, technically sound, and adds a useful datapoint to the growing sample of AGN where CO excitation is spatially resolved. I would send it to a serious referee and expect it to be publishable after minor revision, provided the interpretation stays as carefully hedged as it is in the discussion. I would not desk-reject it, and I would not demand new data; the condition the authors pose is clear and falsifiable.","headline":"Solid, careful ALMA line-ratio work on one radio galaxy; the central observational results hold up, but the multi-kpc cocoon interpretation is honestly flagged by the authors as not unique because of the ongoing merger.","tokens_in":23820,"tokens_out":1791,"would_cite":true,"duration_ms":23046,"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":"Extreme CO line ratios reveal where a radio jet is reshaping cold gas in PKS 0023-26.","keywords":["AGN feedback","cold molecular gas","CO line ratios","radio jets","young radio galaxies","jet-ISM interaction","molecular gas excitation","ALMA observations"],"falsifier":"Spatially resolve CO(1-0), CO(2-1), and CO(3-2) in gas-rich galaxy mergers that lack active nuclei; if regions with R32 > 0.6 extending about 2 to 5 kpc are found in such mergers, the cocoon interpretation for the outer high-excitation region of PKS 0023-26 would need to be abandoned in favour of merger turbulence.","tokens_in":22816,"feed_emoji":"🌌","tokens_out":6502,"duration_ms":63168,"temperature":0.7,"pith_summary":"This paper uses millimetre-wave observations of three carbon monoxide transitions (CO(1-0), CO(2-1), and CO(3-2)) to trace how the jet of a young radio galaxy, PKS 0023-26, affects its cold molecular gas from the nucleus out to several kiloparsecs. The authors establish that the jet's impact shows up in the excitation state and spatial distribution of the gas—extreme CO line ratios aligned with the radio axis, and an absence of CO(1-0) at the radio core—rather than only in gas kinematics, which are strongly disturbed only in the central kiloparsec. The gas appears wrapped around the northern radio lobe, suggesting a strong jet-cloud interaction has destroyed molecular clouds there, while a milder interaction with an expanding jet cocoon excites and stirs gas over larger scales. If this picture holds, AGN feedback can be diagnosed through molecular line ratios and gas distribution even where kinematics show little disturbance, and the energy transferred to the cold gas is a small fraction of the jet power.","feed_headline":"Jet's impact shows up in cold gas excitation, not just motion","feed_subtitle":"ALMA maps three CO transitions in PKS 0023-26, revealing jet effects from the core to several kiloparsecs.","key_machinery":"The central diagnostic is the set of brightness-temperature line ratios R21 and R32 built from three CO transitions observed at matched spatial and spectral resolution. These ratios trace molecular gas excitation and optical depth; extreme values mark gas heated or stirred by the jet and its expanding cocoon, letting the authors map jet influence independently of kinematics. The cocoon of shocked gas created by the jet-ISM interaction, predicted by simulations to expand perpendicular to the jet, provides the mechanism that carries the interpretation of high ratios several kiloparsecs away from the radio axis.","core_discovery":"The paper establishes that in PKS 0023-26, a powerful young radio galaxy, the radio jet modifies the cold molecular interstellar medium in ways that are clearly visible in CO excitation and morphology. The brightness-temperature ratio R32 (CO(3-2)/CO(2-1)) peaks at values of about 1.0 to 1.2 in the region between the core and the northern lobe, and the region with R32 > 0.6 extends roughly 2 to 5 kpc beyond the radio source, with R21 > 1.9 in the central beam where CO(1-0) is undetected. These ratios are far above those of normal star-forming galaxies (R21 around 0.6 and R32 between 0.2 and 0.6). The authors interpret the coincidence of the extreme ratios with the radio emission as evidence of jet-ISM interaction: a destructive interaction at the northern lobe depletes molecular gas there, while a slowly expanding cocoon of shocked gas drives turbulence and high excitation over a larger volume, including perpendicular to the jet. They conclude that AGN impact can be traced through line ratios and gas distribution as well as kinematics, and that most of the jet energy escapes the galaxy.","pith_inferences":["If the cocoon interpretation is correct, other young radio galaxies of similar power should show high R32 regions elongated perpendicular to their jet axes; a statistical study of resolved line ratios could test this pattern.","The paper's own merger caveat suggests a clean control: spatially resolved CO line-ratio imaging of gas-rich galaxy mergers without active nuclei would show whether high excitation regions beyond the radio source are unique to jet-ISM coupling or a generic merger phenomenon.","The non-detection of CO(1-0) at the core could point to X-ray or cosmic-ray heating suppressing low-J CO emission; deep observations of higher-J CO or isotopologues at high angular resolution could separate the heating mechanisms.","The measured low coupling efficiency implies that a full energy budget requires multi-phase measurements—hot X-ray gas, warm ionised gas, and cold molecular gas—rather than a single tracer, to quantify where jet energy is ultimately deposited."],"forward_implications":["Surveys of AGN feedback that rely only on gas kinematics will miss jet influence; spatially resolved mapping of multiple CO transitions is a complementary and sometimes more sensitive tracer.","In young radio galaxies one can expect a spatial stratification of feedback: ejective in the central kiloparsec, destructive at the radio lobes, and a milder, cocoon-driven enhancement of turbulence and excitation on multi-kiloparsec scales.","The small fraction of jet power transferred to the cold gas (kinetic power below about 0.05 percent of the jet power) suggests most of the energy escapes to the circumgalactic medium, so jets may affect galaxy halos more than host ISMs.","High CO excitation in regions oriented perpendicular to radio jets can serve as a signpost for a growing jet cocoon in gas-rich galaxies, extending the diagnostic beyond individual objects.","The coexistence of different interaction modes within one source implies that spatially resolving the full extent of the radio source is necessary to quantify AGN feedback reliably."],"supporting_citations":[{"why":"Supplied the CO(2-1) data and the earlier interpretation of the jet-gas interaction scenario that this paper extends with two additional transitions.","marker":"Morganti et al. (2021)"},{"why":"Simulations predicting the expanding cocoon of shocked gas perpendicular to the jet, used to interpret high line ratios outside the radio source.","marker":"Mukherjee et al. (2016)"},{"why":"Simulations of jet cocoon evolution and energy coupling, cited to support the claim that coupling efficiency declines as the jet breaks out.","marker":"Mukherjee et al. (2018a)"},{"why":"IC 5063 line-ratio study that established the CO excitation signature of jet-ISM interactions and provides the reference values for the ratios observed here.","marker":"Oosterloo et al. (2017)"},{"why":"Provides the typical R21 and R32 values for cold molecular gas in normal star-forming galaxies, the undisturbed reference against which the observed ratios are judged extreme.","marker":"Leroy et al. (2022)"},{"why":"Supplies typical R21 values of star-forming galaxies, supporting the claim that the central R21 > 1.9 is extreme.","marker":"den Brok et al. (2021)"},{"why":"Describes the radio morphology and the VLBI-detected compact component in the northern lobe used to interpret the CO absorption against it.","marker":"Tzioumis et al. (2002)"},{"why":"The cloud-shredding mechanism invoked to explain the depletion of molecular gas at the northern lobe through hydrodynamic instabilities.","marker":"Klein, McKee & Colella (1994)"}],"fun_headline_variants":["Jet's fierce touch alters CO line ratios, not just gas motion","Extreme CO ratios map jet's shock through cold gas","Jet reshapes cold gas: excitation marks the path","AGN jet's imprint seen in CO excitation, beyond motion","Cold gas reveals jet's hidden punch: extreme CO ratios"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the jet cocoon, not the ongoing galaxy merger, produces the high CO excitation beyond the northern lobe and perpendicular to the jet; if merger-driven turbulence alone can produce the same line ratios, the cocoon interpretation for the outer high-excitation region would be unsupported.","fun_headline_variants_meta":{"raw":{"variants":["Jet's fierce touch alters CO line ratios, not just gas motion","Extreme CO ratios map jet's shock through cold gas","Jet reshapes cold gas: excitation marks the path","AGN jet's imprint seen in CO excitation, beyond motion","Cold gas reveals jet's hidden punch: extreme CO ratios"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000711,"raw_usage":{"total_tokens":3312,"prompt_tokens":1168,"completion_tokens":2144,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":784,"completion_tokens_details":{"reasoning_tokens":2061}},"tokens_in":784,"tokens_out":2144,"duration_ms":15826,"temperature":1.0,"reasoning_tokens":2061,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T22:47:19.389095+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Spatially resolve CO(1-0), CO(2-1), and CO(3-2) in gas-rich galaxy mergers that lack active nuclei; if regions with R32 > 0.6 extending about 2 to 5 kpc are found in such mergers, the cocoon interpretation for the outer high-excitation region of PKS 0023-26 would need to be abandoned in favour of merger turbulence.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Describes the radio morphology and the VLBI-detected compact component in the northern lobe used to interpret the CO absorption against it."}],"review_version":1}