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 resultsextendapreviouslypublishedstudyoftheregion.WeshowthatthedegreeofCPcorrelatesspatiallywiththe molecularcloudandappearstobegenerallyverylowinregionsdominatedbyHii.Wedetectafeaturewith3%‐5% CP that extends approximately 60 00 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 asymmetryuponprebioticorganicmoleculesinprotoplanetarydisksarediscussed.Mechanismsinvokedtoexplain 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.