Unveiling deeply embedded sources by near-infrared polarimetric imaging

Near-infrared polarimetric images are presented for six molecular outflow s ources: IRAS 20050+2720, IRAS 20126+4104, IRAS 20188+3928, S233, AFGL 5180, and AFGL 6366S. All the regions are found to exhibit reflection nebulae an d to be associated with massive and clustered star formation. By inspecting polarimetric patterns in the nebulae, we have identified six deeply embedd ed sources (DESs) which illuminate circumstellar nebulosity but are not det ectable in wavelengths shorter than 2 mum While the DES in IRAS 20050 coinc ides with an infrared source in a previous, longer wavelength observation a nd the one in IRAS 20126 with a hot molecular core, the nature of the other newly discovered DESs is not known. From the compilation of the observatio ns of DESs over a large wavelength range, we suspect that the DESs possess characteristics similar to hot molecular cores and are likely to be in the preultracompact H nr region phase of massive star formation.