The molecular envelope around the red supergiant VY CMa

Abstract

We present millimeter interferometric observations of the molecular envelope around the red supergiant VY Cma with the Submillimeter Array (SMA). The high angular resolution (<2”) allows us to derive the structure of the envelope as observed in the 1.3 mm continuum, ¹ ²CO(2–1), ¹ ³O(2–1), and SO(6₅ –5₄ lines emission. The circumstellar envelope is resolved into three components: (1) a dense, compact, and dusty central component, embedded in (2) a more diffuse and extended envelope, and (3) a high-velocity component. We construct a simple model, consisting of a spherically symmetric slowly expanding envelope and bipolar outflows with a wide opening angle (~120 ̊) viewed close to the line of sight (i =15 ̊). Our model can explain the main features of the SMA data and previous single-dish

CO multiline observations. An episode of enhanced mass loss along the bipolar direction is inferred from our modeling. The SMA data provide a better understanding of the complicated morphology seen in the optical /IR high-resolution observations.