Near-infrared Polarimetry of the Massive Young Star W33A in the Godzilla Nebula: Detection of Linear and Circular Polarization

Abstract We have performed the first near-infrared linear and circular imaging polarimetry of the massive W33A star-forming region. Large linear polarization is detected in the very red and extended (∼1 pc projected length) infrared nebulae with a centrosymmetric pattern, suggesting that the IR nebula associated with W33A is the reflection nebula illuminated by the W33A IR source. There is a <10,000 au-scale polarization disk in the vicinity of W33A, probably corresponding to a large pseudodisk. Similar to the other young stars, the circular polarization (CP) image shows a quadrupolar structure around the W33A IR source. However, its degrees are smaller than those previously reported for massive stars. The detection of CP suggests that the origin of CP around young stars is not simple but can be a combination of several causes.