An Extended Search for Circularly Polarized Infrared Radiation from the OMC-1 Region of Orion

Abstract

We present new observations of circular polarization (CP) at 2.2 m in the Orion (OMC-1) molecular cloud. Our results extend a previously published study of the region.We show that the degree of CP correlates spatially with the molecular cloud and appears to be generally very low in regions dominated by H ii.We detect a feature with 3%–5% CP that extends approximately 60" to the southwest of the BN/IRc2 region. Although the morphology of the observed CP is broadly consistent with a model in which radiation from a central source (probably IRc2) is scattered by aligned spheroidal grains, we conclude that dichroic extinction in the foreground molecular cloud also plays a major role in its production. Implications of our results for the hypothesis that CP radiation imposes chiral asymmetry upon prebiotic organicmolecules in protoplanetary disks are discussed.Mechanisms invoked to explain the observed CP in the near infrared can also produce CP in the range of ultraviolet wavelengths capable of chiral selection by photolysis; however, the polarized flux is likely to be of limited spatial extent and to have lower percentage CP compared with the infrared.