Infrared polarization in OMC-1 - Discovery of a molecular hydrogen reflection nebula

The polarization of the broadband continuum at K has been mapped in the core of the OMC-1 with high spatial resolution, and with lower resolution in a more extensive surrounding area. In addition, the first detailed polarization maps in the v = 1-0 S(1) transition from shocked molecular hydrogen were obtained. A self-consistent picture emerges in which IRc2 is the source of a bipolar outflow and the dominant source of continuum radiation from the cloud. The BN object most likely lies behind the flow. Dust grains outside the limit of the flow act to form a reflection nebula (this being the first reported observation of a molecular hydrogen reflection nebula).