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ALMA Reveals the Molecular Outflows in the Ejecta of VY Canis Majoris

Presentation #111.05 in the session Stellar Atmospheres, Winds.

Published onJun 29, 2022
ALMA Reveals the Molecular Outflows in the Ejecta of VY Canis Majoris

Extreme supergiant stars, or hypergiants, experience substantial, sporadic mass loss events that form complex envelope structures composed of arcs, clumps, and knots. The uniformity and regularity of mass loss also significantly modifies evolutionary time scales and affects the geometry of the resulting envelope. The red hypergiant VY CMa is one of the best examples of these types of stars. Previous studies in the infrared of VY CMa of dust emission have shown the presence of distinct arcs to the southwest (Arc 1, Arc 2), a NW arc, and other clumps and knots, many extending several arcseconds from the central star. Using ALMA, we imaged the envelope of VY CMa in multiple molecular lines at Band 6 (1 mm) with 0.25 arcsecond resolution and with the sensitivity to structures as large as 3-4 arcseconds. While some observations are still in progress, preliminary maps of SO, SiO, SO2 and PO has been obtained. From these data, an image of the global molecular outflow structure of VY CMa has been constructed on scales of 6-8 arcseconds. In particular, SO and SO2 emission appears to trace the striking morphology seen in the dust image of VY CMa, including the Arc 2, the NW Arc, among other features. PO, in contrast, is more confined to the inner envelope close to the star. These images will be presented, as well as other new data, and the implications for the evolution of massive stars will be discussed.

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