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arxiv: 2606.11908 · v1 · pith:6MFF33A7new · submitted 2026-06-10 · 🌌 astro-ph.SR · astro-ph.GA

Protostellar Outflows at the EarliesT Stages (POETS). IX. Magnetohydrodynamic disk winds traced by SO and SO₂ in luminous protostars

L. Moscadelli , H. Beuther , A. Sanna , M.T. Beltr\'an , C. Gieser , Th. Henning , P.D. Klaassen , R. Kuiper
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S. Leurini T. M\"oller A. Palau R. E. Pudritz \'A S\'anchez-Monge D. Semenov J.S. Urquhart H. Zinnecker
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Pith reviewed 2026-06-27 08:28 UTC · model grok-4.3

classification 🌌 astro-ph.SR astro-ph.GA
keywords magnetohydrodynamic disk windsprotostellar outflowsSO emissionmassive young stellar objectsKeplerian rotationshock chemistryIRAS21078+5211G035.02+0.35
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The pith

SO emission patterns in two massive protostars indicate a rotating wind launched magneto-centrifugally from the disk surface.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines millimeter observations of molecular lines in two luminous young stellar objects to characterize their protostellar winds at scales of 100 to 1000 au. The spatial distribution and velocity gradients of SO and SO2 align with expectations for a wind that rotates and is launched by magnetic forces from the accretion disk. Position-velocity diagrams show Keplerian-like rotation, and comparisons with shock chemistry models account for why different molecules appear at different distances from the axis. This supports an extended magnetohydrodynamic disk wind model over a compact X-wind scenario for explaining the observations in both sources.

Core claim

In IRAS21078+5211 the molecular emissions lie along the radio jet axis with transverse Vlsr gradients and SO PV plots consistent with Keplerian rotation, while SO2 traces high-velocity gas near the axis and other species extend farther out. In G035.02+0.35 the molecules follow the disk major axis with Keplerian PV profiles and only SO extends outside the disk. In both cases the SO kinematics match a magneto-centrifugally launched rotating wind from the YSO disk, and shock models explain the radial extents via a radially extended MHD DW rather than a compact X-wind.

What carries the argument

Magneto-centrifugally launched rotating disk wind, traced by SO spatial and velocity distributions and tested against shock chemistry models for molecule formation and excitation.

If this is right

  • The different radial extensions of SO, SO2, CH3CN and CH3OH arise from their formation in shocks at varying distances within an extended disk wind.
  • The lack of most molecules except SO in one source's wind is consistent with the same extended MHD DW structure.
  • The transverse velocity gradients directly reflect the rotation of the launched wind material.
  • Similar wind signatures appear in both studied YSOs despite differences in their disk versus jet alignments.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Disk winds may remove angular momentum over larger radial ranges than compact launch models allow in massive star formation.
  • Multi-molecule mapping could distinguish wind structures across a wider sample of protostars.
  • Refined shock models incorporating wind density profiles might predict additional observable tracers.

Load-bearing premise

The transverse velocity gradients and Keplerian position-velocity plots arise directly from a magneto-centrifugally launched wind originating at the disk surface.

What would settle it

If observations at higher angular resolution reveal velocity patterns inconsistent with Keplerian rotation in the SO-emitting gas, or if X-wind models can reproduce the observed molecular radial extents without an extended wind component.

Figures

Figures reproduced from arXiv: 2606.11908 by A. Palau, \'A S\'anchez-Monge, A. Sanna, C. Gieser, D. Semenov, H. Beuther, H. Zinnecker, J.S. Urquhart, L. Moscadelli, M.T. Beltr\'an, P.D. Klaassen, R. E. Pudritz, R. Kuiper, S. Leurini, Th. Henning, T. M\"oller.

Figure 1
Figure 1. Figure 1: Rotating wind in IRAS 21078+5211 (panel a) and G035.02+0.35 (panel b). In both panels, the grayscale and color maps in the upper and lower plots correspond to the velocity-integrated emission and intensity-weighted velocity, respectively, of the SO 65– 54 line. The green color represents VLSR close to the systemic velocity. (Panel a) The level contours of the grayscale filled-contours map in the upper plot… view at source ↗
Figure 2
Figure 2. Figure 2: Structure and kinematics of the IRAS 21078 [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Structure and kinematics of the G035.02+0.35 disk in molecular tracers. Each of the four panels presents the maps of the velocity-integrated emission (upper plot) and intensity-weighted velocity (lower plot) for a specific molecular line, as labeled. The level contours of the grayscale filled-contours maps in the upper plots are 5%, 15%, and from 30% to 80% in steps of 10% of the map peak. The thick green … view at source ↗
Figure 4
Figure 4. Figure 4: Gas kinematics in IRAS 21078+5211. Each of the four panels presents the PV plot along the cut at PA = 140◦ (marked by the dashed black line in Figs. 1 and 2) of the molecular line specified above the panel. PV plots are shown with color maps and white contours, with contour levels ranging from |Imin| /2 to Imax at steps of |Imin| /2, where Imin and Imax are the mini￾mum and maximum of the map, respectively… view at source ↗
read the original abstract

We investigate two massive young stellar objects (YSOs), IRAS21078+5211 and G035.02+0.35, where evidence for magnetohydrodynamic (MHD) disk winds (DWs) has been obtained at scales of 10-100 au through measurements of the 22GHz water maser velocity distribution within the Protostellar Outflows at the EarliesT Stages (POETS) survey. We employ IRAM Northern Extended Millimeter Array and archival Atacama Large Millimeter Array observations of IRAS21078+5211 and G035.02+0.35, respectively, to study kinematics and physical conditions of the corresponding protostellar winds on scales of 100-1000 au using the same molecular tracers. In IRAS21078+5211, the emissions of several molecules, particularly SO, SO2, CH3CN and CH3OH, are distributed along the axis of the radio jet, and present a LSR velocity (Vlsr) gradient transversal to the jet axis. Position-velocity (PV) plots of the SO lines show patterns consistent with Keplerian rotation. The SO2 emission comes from high velocity gas flowing close to the jet axis, while CH3CN and CH3OH present larger radial extension than the S-bearing species. In G035.02+0.35, the same molecules are instead distributed along the major axis of the rotating disk, and their Vlsr gradients consistently trace the disk rotation. The corresponding PV plots present Keplerian profiles. SO is the only molecular species whose emission extends well outside the disk. In both YSOs, the spatial and velocity distributions of SO are consistent with a rotating wind magneto-centrifugally launched from the YSO disk. The comparison with models of molecule formation and excitation in shocks indicates that the different radial extension of the molecular species observed in the protostellar wind of IRAS21078+5211, as well as the lack of molecules, except SO, in the G035.02+0.35's wind, can be explained in terms of a radially extended MHD DW, rather than a compact X-wind.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript presents IRAM NOEMA and archival ALMA observations of SO, SO2, CH3CN, and CH3OH toward two luminous YSOs (IRAS21078+5211 and G035.02+0.35). It reports transverse V_LSR gradients and Keplerian-like PV diagrams for SO, argues that these trace a magneto-centrifugally launched rotating disk wind on 100-1000 au scales, and concludes that the differing radial extents of the species (and the absence of most molecules in the G035.02+0.35 wind) are explained by shock-chemistry models for a radially extended MHD disk wind rather than a compact X-wind.

Significance. If the kinematic interpretation and model comparison hold, the work would extend the POETS water-maser evidence for MHD disk winds to larger scales using thermal molecular lines and provide a potential observational discriminator between extended disk-wind and X-wind scenarios via chemistry. The multi-tracer approach and direct comparison to shock models are strengths that could be impactful for massive-star formation studies.

major comments (2)
  1. [kinematics section for IRAS21078+5211] Abstract and the section on IRAS21078+5211 kinematics: the claim that SO PV plots are 'consistent with Keplerian rotation' and trace a magneto-centrifugally launched wind is load-bearing, yet the text presents only qualitative patterns without reported best-fit rotation-curve parameters, residuals, or formal comparison to the expected MHD wind velocity field (e.g., no χ^{2} values or parameter uncertainties).
  2. [model comparison section] The section comparing to shock-chemistry models: the manuscript states that the models explain the radial extents of SO/SO2 versus CH3CN/CH3OH without additional wind-structure parameters, but does not demonstrate that the models were run with parameters fixed solely from the observed MHD DW geometry or that alternative (X-wind) geometries were quantitatively ruled out; this is the weakest step in distinguishing the two scenarios.
minor comments (2)
  1. [abstract] Abstract: no mention of observed transitions, beam sizes, or rms noise levels; these details should be added for completeness.
  2. [figures] Figure captions and text: ensure consistent use of V_LSR versus Vlsr and explicit labeling of velocity gradient directions and units on all PV diagrams.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed report. The comments highlight areas where the kinematic and model-comparison sections can be strengthened with additional quantitative detail. We address each point below and will incorporate revisions accordingly.

read point-by-point responses

  1. Referee: [kinematics section for IRAS21078+5211] Abstract and the section on IRAS21078+5211 kinematics: the claim that SO PV plots are 'consistent with Keplerian rotation' and trace a magneto-centrifugally launched wind is load-bearing, yet the text presents only qualitative patterns without reported best-fit rotation-curve parameters, residuals, or formal comparison to the expected MHD wind velocity field (e.g., no χ² values or parameter uncertainties).

    Authors: We agree that the kinematic interpretation is central and that the current presentation relies on qualitative assessment of the PV diagrams. In the revised manuscript we will add least-squares fits to the SO position-velocity data, reporting the best-fit rotation-curve parameters, residuals, and formal uncertainties. These will be compared directly to the expected velocity field of a magneto-centrifugal disk wind, including χ² statistics where appropriate. This addition will make the supporting evidence for the claimed rotation explicit. revision: yes

  2. Referee: [model comparison section] The section comparing to shock-chemistry models: the manuscript states that the models explain the radial extents of SO/SO2 versus CH3CN/CH3OH without additional wind-structure parameters, but does not demonstrate that the models were run with parameters fixed solely from the observed MHD DW geometry or that alternative (X-wind) geometries were quantitatively ruled out; this is the weakest step in distinguishing the two scenarios.

    Authors: We acknowledge that the model-comparison section would benefit from greater transparency on parameter choices and on the quantitative distinction from an X-wind geometry. In the revision we will (i) tabulate the exact shock-chemistry model inputs and show they are taken directly from the observed disk-wind geometry (radius, velocity, density) without additional free parameters, and (ii) present a side-by-side comparison of predicted radial extents for both the extended MHD disk-wind and compact X-wind cases, including a brief discussion of why the latter is disfavored by the data. We note that a fully exhaustive statistical exclusion of every X-wind variant lies beyond the scope of the present observations, but the revised text will make the existing model constraints explicit. revision: yes

Circularity Check

0 steps flagged

Derivation chain is self-contained with no circular reductions

full rationale

The paper's claims rest on direct observational data (Vlsr gradients, PV plots of SO/SO2/CH3CN/CH3OH) and qualitative comparison to independent shock-chemistry models for radial extents. The POETS water-maser reference supplies prior context at smaller scales but is not load-bearing for the new 100-1000 au conclusions or the distinction from X-winds. No self-definitional loops, fitted inputs renamed as predictions, or ansatzes smuggled via self-citation appear in the provided text. The derivation remains externally falsifiable against the cited models and does not reduce to its own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

Only the abstract is available; no explicit free parameters, invented entities, or ad-hoc axioms are stated. The interpretation assumes standard Keplerian rotation and standard shock-chemistry models from the literature.

axioms (2)
  • domain assumption Position-velocity diagrams showing linear or Keplerian patterns trace rotation in a disk or wind launched from a disk.
    Invoked when interpreting PV plots of SO lines as consistent with Keplerian rotation in both sources.
  • domain assumption Shock-chemistry and excitation models from the literature accurately predict the observed radial extents of SO, SO2, CH3CN and CH3OH in protostellar winds.
    Used to conclude that the data favor a radially extended MHD DW over a compact X-wind.

pith-pipeline@v0.9.1-grok · 6046 in / 1519 out tokens · 20187 ms · 2026-06-27T08:28:36.650551+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

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Reference graph

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