Young stars are associated with prominent outflows of molecular gas1,2. The ejection of gas is believed to remove angular momentum from the protostellar system, permitting young stars to grow by the accretion of material from the protostellar disk2. The underlying mechanism for outflow ejection is not yet understood2, but is believed to be closely linked to the protostellar disk3. Various models have been proposed to explain the outflows, differing mainly in the region where acceleration of material takes place: close to the protostar itself (‘X-wind’4,5, or stellar wind6), in a larger region throughout the protostellar disk (disk wind7,8,9), or at the interface between the two10. Outflow launching regions have so far been probed only by indirect extrapolation11,12,13 because of observational limits. Here we report resolved images of carbon monoxide towards the outflow associated with the TMC1A protostellar system. These data show that gas is ejected from a region extending up to a radial distance of 25 astronomical units from the central protostar, and that angular momentum is removed from an extended region of the disk. This demonstrates that the outflowing gas is launched by an extended disk wind from a Keplerian disk.
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We thank M. Bizzarro and L. Kristensen for suggestions that improved the paper. This research was supported by the Swedish Research Council through contract 637-2013-472 (to P.B.). M.H.D.v.d.W. and J.K.J. acknowledge support by a Lundbeck Foundation Junior Group Leader Fellowship as well as the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 646908) through ERC Consolidator Grant ‘S4F’. The Centre for Star and Planet Formation is funded by the Danish National Research Foundation. D.H. is funded by the Deutsche Forschungsgemeinschaft Schwerpunktprogramm (DFG SPP 1385) ‘The First 10 Million Years of the Solar System—A Planetary Materials Approach’. We also thank the staff at the Nordic ALMA Regional Centre node for assistance with the preparation and calibration of the data. D.H. thanks Leiden Observatory for providing the computing facilities. This paper makes use of ALMA data (see Methods section ‘Data availability’). ALMA is a partnership of the ESO (representing its member states), the NSF (USA) and NINS (Japan), together with the NRC (Canada), the NSC and ASIAA (Taiwan), and the KASI (South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by the ESO, AUI/NRAO and NAOJ.
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Nature Astronomy (2017)