New Results on the Submillimeter Polarization Spectrum of the Orion Molecular Cloud

TL;DR

This study maps the polarization spectrum of the Orion Molecular Cloud at 350 and 450 microns, revealing variations in polarization ratios that inform dust grain properties and magnetic field structures.

Contribution

It provides new submillimeter polarization measurements of the Orion Molecular Cloud, highlighting wavelength-dependent polarization ratios and their spatial variations.

Findings

Polarization ratio ~1.3 in outer cloud regions

Ratio drops by a factor of 2 near KL nebula

Minimum polarization ratio occurs around 350 microns

Abstract

We have used the SHARP polarimeter at the Caltech Submillimeter Observatory to map the polarization at wavelengths of 350 and 450 micron in a ~2 x 3 arcmin region of the Orion Molecular Cloud. The map covers the brightest region of the OMC-1 ridge including the Kleinmann-Low (KL) nebula and the submillimeter source Orion-south. The ratio of 450-to-350 micron polarization is ~ 1.3 +/- 0.3 in the outer parts of the cloud and drops by a factor of 2 towards KL. The outer cloud ratio is consistent with measurements in other clouds at similar wavelengths and confirms previous measurements placing the minimum of the polarization ratio in dusty molecular clouds at a wavelength ~ 350 micron.