Near-Infrared Imaging Polarimetry of S106 Cluster-Forming Region with SIRPOL

We present the results of wide-field JHKs polarimetry toward the HII region S106 using the IRSF (Infrared Survey Facility) telescope. Our polarimetry data revealed an extended (up to ~ 5') polarized nebula over S106. We confirmed the position of the illuminating source of most of the nebula as consistent with S106 IRS4 through an analysis of polarization vectors. The bright portion of the polarized intensity is consistent with the red wing component of the molecular gas. Diffuse polarized intensity emission is distributed along the north--south molecular gas lanes. We found the interaction region between the radiation from S106 IRS4 and the dense gas. In addition, we also discovered two small polarization nebulae, SIRN1 and SIRN2, associated with a young stellar objects (YSO). Aperture polarimetry of point-like sources in this region was carried out for the first time. The regional magnetic field structures were derived using point-like source aperture polarimetry, and the magnetic field structure position angle around the cluster region in S106 was found to be ~ 120$\arcdeg$. The magnetic fields in the cluster region, however, have three type position angles: ~ 20$\arcdeg$, ~ 80$\arcdeg$, and ~ 120$\arcdeg$. The present magnetic field structures are consistent with results obtained by submillimeter continuum observations. We found that the magnetic field direction in the dense gas region is not consistent with that of the low density gas region.