Polarimetric mapping of a new infrared reflection nebula GGD 27 IRS

Abstract

We report the discovery of an infrared reflection nebula GGD27 IRS, near the optical nebulosity GGD27. It shows a dumbbell-shaped structure with large degrees of polarization, up to 64%, in the K band. From the centrosymmetric pattern of the polarization vectors we identify the illuminating source of the nebula with IRS 2. A simple model based on single Rayleigh scattering at the surface of a paraboloidal shell gives good agreement with the observed radial dependence of both polarization and surface brightness. This model is in good agreement with the recently revealed shell structure of the CO bipolar flow. Small polarization and low surface brightness both east and west of IRS 2 indicate the presence of a disk of obscuring material elongated orthogonal to the extent of the nebula. We estimate the size, extinction, and mass of the disk to be 40" x 60", 75 mag and 200 Mo, respectively.