Arcsecond resolution mapping of Sulfur Dioxide emission in the
  circumstellar envelope of VY Canis Majoris
  We report Submillimeter Array observations of SO2 emission in the
circumstellar envelope of the red supergiant VY CMa, 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 ~10^16 cm^-2 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 greater than at least
3x10^16 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/f_SO>1 and may suggest the role of localized
effects such as shocks in the production of SO2 in the circumstellar envelope.
