The Three-Dimensional Morphology of VY Canis Majoris. II. Polarimetry and the Line-of-Sight Distribution of the Ejecta

We use imaging polarimetry taken with the HST/ACS/HRC to explore the threedimensional structure of the circumstellar dust distribution around the redsupergiant VY Canis Majoris. The polarization vectors of the nebulositysurrounding VY CMa show a strong centro-symmetric pattern in all directionsexcept directly East and range from 10% - 80% in fractional polarization. Inregions that are optically thin, and therefore likely have only singlescattering, we use the fractional polarization and photometric color to locatethe physical position of the dust along the line-of-sight. Most of theindividual arc-like features and clumps seen in the intensity image are alsofeatures in the fractioanl polarization map. These features must be distinctgeometric objects. If they were just local density enhancements, the fractionalpolarization would not change so abruptly at the edge of the feature. Thelocation of these features in the ejecta of VY CMa using polarimetry provides adetermination of their 3D geometry independent of, but in close agreement with,the results from our study of their kinematics (Paper I).