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Snapshot of a magnetohydrodynamic disk wind traced by water maser observations


The formation of astrophysical objects of different nature, from black holes to gaseous giant planets, involves a disk–jet system, where the disk drives the mass accretion onto a central compact object and the jet is a fast collimated ejection along the disk rotation axis. Magnetohydrodynamic disk winds can provide the link between mass accretion and ejection, which is essential to ensure that the excess angular momentum is removed and accretion can proceed. However, until now, we have been lacking direct observational proof of disk winds. Here we present a direct view of the velocity field of a disk wind around a forming massive star. Achieving a very high spatial resolution of about 0.05 au, our water maser observations trace the velocities of individual streamlines emerging from the disk orbiting the forming star. We find that, at low elevation above the disk midplane, the flow co-rotates with its launch point in the disk, in agreement with magneto-centrifugal acceleration. Beyond the co-rotation point, the flow rises spiralling around the disk rotation axis along a helical magnetic field. We have performed (resistive-radiative-gravito-)magnetohydrodynamic simulations of the formation of a massive star and record the development of a magneto-centrifugally launched jet presenting many properties in agreement with our observations.

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Fig. 1: Previous NOEMA, JVLA and VLBA observations towards IRAS 21078+5211.
Fig. 2: Global VLBI observations of the 22 GHz water masers and 3D view of the proposed kinematical interpretation.
Fig. 3: The geometry of the spiral motion.
Fig. 4: The southwest spiral motion.
Fig. 5: The northeast spiral motions.
Fig. 6: The co-rotating north stream.

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Data availability

This article makes use of the following EVN data: GM077 (EVN project code). The calibrated datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Code availability

The custom parts of the code for producing the simulations and subsequent data analysis are not ready for public use, but they can be provided upon reasonable request. For the magnetohydrodynamics part of the software, we make use of the open-source code Pluto35,41. The implementation method of the employed radiation transport module (‘Makemake’) is publicly accessible38.


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We thank C. Fendt and D. Galli for useful discussion. A.O. acknowledges financial support from the Deutscher Akademischer Austauschdienst (DAAD), under the programme Research Grants - Doctoral Projects in Germany, and complementary financial support for the completion of the doctoral degree by the University of Costa Rica, as part of their scholarship programme for postgraduate studies in foreign institutions. H.B. acknowledges support from the European Research Council under the Horizon 2020 Framework Programme via the ERC Consolidator Grant CSF-648505. H.B. also acknowledges support from the Deutsche Forschungsgemeinschaft in the Collaborative Research Center (SFB 881) ‘The Milky Way System’ (subproject B1). R.K. acknowledges financial support via the Emmy Noether and Heisenberg Research Grants funded by the German Research Foundation (DFG) under grant numbers KU 2849/3 and 2849/9. The European VLBI Network is a joint facility of independent European, African, Asian and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code: GM077.

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Authors and Affiliations



L.M. led the project, analysis, discussion and drafted the manuscript. A.S., H.B. and R.K. commented on the manuscript and participated in the discussion. A.O. and R.K. performed the numerical jet simulations described in ‘Simulation snapshot of a forming massive star’ in Methods. A.O. performed the dynamical analysis of the simulations, compared the simulation results to the observations, and produced the illustrations of the magnetic-field lines and streamlines.

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Correspondence to Luca Moscadelli.

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Supplementary Information

Supplementary Figs. 1–7 and Discussion (with 3 distinct headings).

Supplementary Table 1

Table (in text format) listing the properties (label, Intensity, VLSR, right ascension and declination positional offsets) of the observed water masers.

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Moscadelli, L., Sanna, A., Beuther, H. et al. Snapshot of a magnetohydrodynamic disk wind traced by water maser observations. Nat Astron 6, 1068–1076 (2022).

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