ALMA Reveals Unexpected Structures in the Envelope of Hypergiant VY CMa

Massive RSG stars undergo intense mass loss on their late stages, showing complex non-isotropic envelopes with highly directional outflows. VY Canis Majoris (VY CMa) is one of the best examples of such massive stars, with an envelope that is dominated by arcs, clumps and knots. Using ALMA at Band 6 with ~1 and ~0.25-arcsecond resolution, combined with previous single-dish observations, VY CMa has been imaged in CO and HCN. From the combined data sets, all flux from the molecular envelope has been recovered, resulting in the first complete image of the ejecta on a maximum angular scale of 25 arcsecond. New, previously unrecognized large-scale structures have been discovered in CO and HCN emission, as well as previously known features such as Arcs1 and 2 and the NW Arc. The new structures exist as far as 8 arcseconds from the star, including a NE plume and an E arc. Additionally, images of ¹³CO and H¹³CN have been obtained to compare isotopic ratio variations. These data complement previous studies conducted on smaller spatial scales and provide the most complete portrait of the mass loss history of VY CMa to date.