{"id":"edf66214-431b-409b-8acc-62aae0e75454","arxiv_id":"2606.04084","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":7.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":2,"one_line_summary":"Self-regulating AGN jets in MHD simulations of cool-core clusters yield realistic FRI radio morphologies viewed along the jet axis and account for frequency-independent lobe extents via 1-50 μG fields allowing both young and old electrons to radiate.","lead":"Researchers performed magneto-hydrodynamical simulations of self-regulating AGN jets in an idealised Perseus-like cool-core cluster, evolving cosmic ray electrons along tracers with the Crest solver to generate mock radio observations. The work shows that feedback-regulated jets produce realistic FRI morphologies and explains why cluster-scale radio lobes can appear similar in extent across 150 MHz to 1.4 GHz frequencies.","discovery_kind":"unclear","skeptic_critique":{"model":"grok-4.3","headline":"Sub-grid CR acceleration + Crest Fokker-Planck on tracers may not yield observationally accurate synchrotron maps for the claimed FRI morphologies","rationale":"The reader correctly isolates the CR sub-grid + Crest step as the weakest link for the morphology claim. Because the abstract supplies no quantitative validation of that step against real radio data, the “realistic FRI” assertion remains unanchored; the stabilization result is less affected. This matches the reader’s weakest_assumption exactly, so the UNVERDICTED verdict is left unchanged.","tokens_in":1809,"tokens_out":409,"duration_ms":12644,"concrete_test":"Extract the simulated 150 MHz and 1.4 GHz surface-brightness maps for the self-regulated run; compute the median spectral index between those frequencies inside the lobes and the ratio of lobe extents at the two frequencies. Compare both quantities to published VLA/LOFAR maps of Perseus or similar cool-core FRI sources; a >30% mismatch in either metric indicates the sub-grid + Crest combination does not yet reproduce the claimed observational realism.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim requires that the mock radio images (viewed along the jet axis) genuinely reproduce observed FRI lobe structures and frequency-dependent extents. This rests on (1) the unspecified sub-grid prescription that injects and accelerates CR protons/electrons at the jet, and (2) the subsequent Lagrangian tracer evolution with Crest under the simulated B-fields (1-50 μG). No independent calibration or direct spectral-index/luminosity comparison to real Perseus FRI sources is described in the abstract; the contrast to “symmetrical lobes from fixed-power outbursts” therefore inherits any systematic bias in the CR injection or loss terms. If the sub-grid model over- or under-predicts the population of ~GeV electrons that radiate at 150 MHz–1.4 GHz, the reported morphological realism and the explanation for equal spatial extents at different frequencies both weaken.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript presents MHD simulations of an idealized Perseus-like cool-core cluster in which accretion-powered jets self-regulate via a sub-grid cosmic-ray acceleration model. Electron spectra are evolved along Lagrangian tracers with the Crest Fokker-Planck solver to generate mock synchrotron maps viewed along the jet axis; the central claims are that these self-regulated jets stabilize the core against cooling flows, produce realistic FRI and disturbed lobe morphologies (unlike symmetric lobes from fixed-power outbursts), and explain the observational fact of similar lobe extents at 150 MHz–1.4 GHz in the simulated 1–50 μG fields.","tokens_in":1996,"tokens_out":508,"duration_ms":16192,"significance":"If the mock radio images are shown to be quantitatively consistent with observations, the work would strengthen the case that self-regulated AGN feedback can simultaneously quench cooling flows and reproduce complex FRI structures. A clear strength is the self-consistent coupling of evolved magnetic fields with the Crest-evolved electron spectra, which directly addresses the frequency-extent puzzle without ad-hoc assumptions about electron populations.","major_comments":[{"comment":"Abstract: the headline claim that the simulations 'produce realistic Fanaroff-Riley I (FRI) and disturbed lobe morphologies' is load-bearing for the paper's main result, yet the abstract (and the provided summary) supplies no quantitative metrics such as lobe asymmetry indices, surface-brightness profiles, or direct spectral-index comparisons to observed Perseus FRI sources; without these, it is impossible to assess whether the sub-grid CR model plus Crest evolution actually reproduces the target morphologies.","section":"Abstract"},{"comment":"Abstract: the explanation that 'both freshly accelerated and hundreds-of-Myr-old electrons are able to contribute to the 150 MHz–1.4 GHz frequency range' in 1–50 μG fields rests on the accuracy of the unspecified sub-grid CR acceleration efficiency and the subsequent Fokker-Planck losses; no calibration, sensitivity tests, or comparison of predicted luminosities/spectral indices against real Perseus data are described, directly affecting the robustness of both the morphological and frequency-extent claims.","section":"Abstract"}],"minor_comments":[{"comment":"The term 'blazar configuration' for the line-of-sight viewing angle should be defined or replaced with a clearer description of the projection geometry.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for their constructive comments on our manuscript. We respond to each major comment below.","responses":[{"response":"We agree that the abstract's use of 'realistic' would be strengthened by quantitative metrics. The manuscript demonstrates the key physical result through direct comparison: self-regulated jets produce complex, disturbed lobe structures via deflection by cold gas, in contrast to the symmetric lobes from fixed-power outbursts. This qualitative distinction is shown in the figures and arises self-consistently from the simulation physics. We will revise the abstract to state that the simulations 'produce complex FRI-like and disturbed lobe morphologies' to more accurately reflect the nature of the comparison presented.","revision_made":"partial","referee_comment":"[Abstract] Abstract: the headline claim that the simulations 'produce realistic Fanaroff-Riley I (FRI) and disturbed lobe morphologies' is load-bearing for the paper's main result, yet the abstract (and the provided summary) supplies no quantitative metrics such as lobe asymmetry indices, surface-brightness profiles, or direct spectral-index comparisons to observed Perseus FRI sources; without these, it is impossible to assess whether the sub-grid CR model plus Crest evolution actually reproduces the target morphologies."},{"response":"The sub-grid cosmic-ray acceleration model, including the efficiency parameter, is fully specified in the methods section, with values drawn from standard AGN jet models. Magnetic fields are evolved self-consistently in the MHD simulation and reach 1–50 μG in the lobe regions. The Crest Fokker-Planck solver then evolves the electron spectra including all relevant losses. This setup directly shows that, for these B-field strengths, synchrotron frequencies in the 150 MHz–1.4 GHz range receive contributions from both young and old electrons. The simulation is idealized and not tuned to match specific Perseus luminosities or spectral indices; the goal is to illustrate the mechanism for frequency-independent extents. We will add a short paragraph in the revised manuscript discussing the model assumptions and parameter choices.","revision_made":"partial","referee_comment":"[Abstract] Abstract: the explanation that 'both freshly accelerated and hundreds-of-Myr-old electrons are able to contribute to the 150 MHz–1.4 GHz frequency range' in 1–50 μG fields rests on the accuracy of the unspecified sub-grid CR acceleration efficiency and the subsequent Fokker-Planck losses; no calibration, sensitivity tests, or comparison of predicted luminosities/spectral indices against real Perseus data are described, directly affecting the robustness of both the morphological and frequency-extent claims."}],"tokens_in":1542,"tokens_out":547,"duration_ms":25192,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main thing to know is that these simulations of a Perseus-like cool-core cluster show self-regulated AGN jets stabilizing the core while producing complex, deflected FRI-like radio lobes when viewed along the axis, in contrast to the symmetric structures from a single fixed-power outburst. They also account for the observed similar spatial extents at 150 MHz and 1.4 GHz because both fresh and aged electrons radiate in the 1-50 μG fields.\n\nWhat is new is the combination of accretion-responsive jet feedback with Lagrangian tracers running the Crest Fokker-Planck solver to evolve cosmic-ray electron spectra alongside the MHD fields. This produces the mock observations and highlights how cold gas deflects the light jets, so kpc-scale lobe shapes do not reveal small-scale black-hole or jet details.\n\nThe setup works well for demonstrating that contrast and for linking the magnetic-field and electron evolution to the frequency-independent extents. The method is a clear step past simpler fixed-power or single-outburst runs.\n\nThe soft spot is the sub-grid prescription that accelerates cosmic-ray protons and electrons at the jet. The morphological realism and the equal-extent claim both depend on whether that injection plus the subsequent losses accurately populate the ~GeV electrons that emit in the observed bands. The abstract supplies no quantitative spectral-index or luminosity matches to real Perseus sources, so the stress-test concern about the accuracy of the synchrotron maps stands. Without calibration or direct comparison metrics, the interpretation for observations stays provisional.\n\nThis is for people running or using AGN feedback simulations in clusters and for observers who want mock radio data. A reader focused on methodological advances in tracer-based CR evolution would find it useful. The work shows clear engagement with the modeling problem and deserves peer review to examine the sub-grid choices and any validation added in the full text.","headline":"Self-regulated jets here give disturbed FRI morphologies and explain equal lobe extents across frequencies via the tracer-evolved electrons, but the result rests on an uncalibrated sub-grid CR acceleration model.","tokens_in":2496,"tokens_out":446,"would_cite":false,"duration_ms":17717,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Self-regulated AGN jets in cool-core clusters produce realistic Fanaroff-Riley I radio morphologies and prevent cooling flows.","keywords":["AGN jets","cool-core galaxy clusters","Fanaroff-Riley I morphologies","cosmic ray electrons","radio synchrotron emission","self-regulated feedback","Fokker-Planck evolution"],"falsifier":"If multi-frequency radio maps of cool-core clusters like Perseus show symmetric lobes despite ongoing AGN activity, or if lobe spatial extents differ markedly between 150 MHz and 1.4 GHz in regions with 1-50 microGauss fields, the central claims would be challenged.","tokens_in":2723,"feed_emoji":"📡","tokens_out":855,"duration_ms":23485,"temperature":0.7,"pith_summary":"The paper uses magneto-hydrodynamical simulations of an idealized Perseus-like galaxy cluster where accretion powers low-density jets. These jets accelerate cosmic rays via a sub-grid model, and cosmic ray electron spectra are evolved along Lagrangian tracers with the Crest Fokker-Planck solver to generate synchrotron radio emission. The central result is that self-regulated jets stabilize the cluster core against cooling flows and yield complex, disturbed Fanaroff-Riley I lobe shapes. In contrast, a single fixed-power outburst produces only symmetrical lobes. Mock observations viewed along the jet axis still display complex structures because light jets are deflected by cold gas structures, and the model accounts for similar radio lobe extents across 150 MHz to 1.4 GHz frequencies in the simulated 1-50 microGauss magnetic fields.","feed_headline":"Self-regulated jets stabilize clusters and shape realistic radio lobes","feed_subtitle":"Simulations show accretion-powered jets deflect to create disturbed FRI structures while stopping cooling flows.","key_machinery":"Self-regulating accretion-powered low-density AGN jets with a sub-grid cosmic ray acceleration model, using the Crest Fokker-Planck solver to evolve electron spectra along Lagrangian tracers and compute radio synchrotron emission.","core_discovery":"Self-regulated AGN jets stabilize the cool-core cluster against cooling flows and produce realistic Fanaroff-Riley I (FRI) and disturbed lobe morphologies, in contrast to symmetrical lobe structures obtained with a single jet outburst of fixed power. Our mock radio observations are viewed in a blazar configuration - along the jet axis - and exhibit complex radio-emitting lobe structures despite this. This highlights the strong deflection of light jets by cold gas structures and suggests that small-scale black hole and jet properties cannot be inferred from kpc-scale FRI radio lobe morphologies. Combining self-consistently evolved magnetic fields and electron spectra enables us to explain a k","pith_inferences":["Jet deflection by cold gas structures may be a general process limiting what can be inferred about jet launching from large-scale radio maps.","The same simulation framework could be used to predict how radio morphologies evolve in clusters with different masses or dynamical states.","If the sub-grid cosmic ray model is accurate, these simulations provide a way to interpret upcoming wide-field radio surveys of galaxy clusters."],"forward_implications":["Self-regulated jets maintain thermal balance in the cluster core by responding to accretion rates.","Disturbed FRI morphologies arise primarily from jet deflection by cold gas rather than variations in jet power.","Small-scale properties of the central black hole and jets cannot be directly read from observed kpc-scale lobe shapes.","Both young and old cosmic ray electrons contribute to radio emission across 150 MHz to 1.4 GHz in typical cool-core magnetic fields."],"fun_headline_variants":["Self-regulated jets deflect to shape realistic FRI lobes","Cold gas deflects light jets forming complex radio lobes","Self-regulating AGN prevents cluster cooling with FRI structures","Blazar views reveal deflected cluster lobe morphologies"],"cache_read_input_tokens":64,"weakest_assumption_plain":"The sub-grid model used to accelerate cosmic ray protons and electrons by the jets, when combined with the Fokker-Planck evolution in Crest along Lagrangian tracers, produces radio synchrotron emission that accurately represents real observations.","fun_headline_variants_meta":{"raw":{"variants":["Self-regulated jets deflect to shape realistic FRI lobes","Cold gas deflects light jets forming complex radio lobes","Self-regulating AGN prevents cluster cooling with FRI structures","Blazar views reveal deflected cluster lobe morphologies"]},"model":"grok-4.3","cost_usd":0.005187,"raw_usage":{"total_tokens":2576,"prompt_tokens":787,"num_sources_used":0,"completion_tokens":58,"cost_in_usd_ticks":51874500,"prompt_tokens_details":{"text_tokens":787,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1731,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":787,"tokens_out":58,"duration_ms":10272,"temperature":1.0,"reasoning_tokens":1731,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-28T08:53:41.410212+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"If multi-frequency radio maps of cool-core clusters like Perseus show symmetric lobes despite ongoing AGN activity, or if lobe spatial extents differ markedly between 150 MHz and 1.4 GHz in regions with 1-50 microGauss fields, the central claims would be challenged.","supporting_citations":[],"review_version":1}