2012ApJ...746...42F

We report Submillimeter Array observations of SO₂ emission in the circumstellar envelope (CSE) of the red supergiant VY Canis Majoris, with an angular resolution of ~1''. SO₂ emission appears in three distinct outflow regions surrounding the central continuum peak emission that is spatially unresolved. No bipolar structure is noted in the sources. A fourth source of SO₂ is identified as a spherical wind centered at the systemic velocity. We estimate the SO₂ column density and rotational temperature assuming local thermal equilibrium (LTE) as well as perform non-LTE radiative transfer analysis using RADEX. Column densities of SO₂ are found to be ∼10¹⁶/cm2 in the outflows and in the spherical wind. Comparison with existing maps of the two parent species OH and SO shows the SO₂ distribution to be consistent with that of OH. The abundance ratio f_SO2/f_SO is greater than unity for all radii larger than 3x10¹⁶ cm. SO₂ is distributed in fragmented clumps compared to SO, PN, and SiS molecules. These observations lend support to specific models of circumstellar chemistry that predict f_SO2_/fSO_ > 1 and may suggest the role of localized effects such as shocks in the production of SO₂ in the CSE.