Outflows from luminous young stellar objects: An infrared polarimetric study

We present near-infrared imaging polarimetry of three regions of massive star formation, G192.16-3.82, Cep A, and W42. In W42 we have discovered a new bipolar nebula located at the far side of the H II region behind the visible cluster of exciting stars. The axis of this new nebula is aligned with the magnetic field threading the entire cluster region. Polarization in the bipolar outflow nebulosity associated with G192.16 is consistent with a single illuminating source, too faint to be detected at 2 μm. Polarization in the reflection nebulosity associated with Cep A requires more than one illuminating source, although HW 2 is clearly dominant. In all three objects, the magnetic field in the outflow at distances greater than ∼0.2 pc is radial. In G192. 16 the magnetic field geometry closer than ∼0.2 pc to the embedded star appears chaotic. For G192.16 the outflow is not aligned with the surrounding magnetic field, which lies in the Galactic plane. In Cep A, the outflow axis could be interpreted as being aligned with the Galactic plane, but the magnetic field threading the region is not. Only in the case of W42 is the magnetic field threading the H II region aligned with the mean field in the surrounding Galactic plane.