Submillimeter Polarization Spectrum of the Carina Nebula

TL;DR

This study measures the submillimeter polarization spectrum of the Carina Nebula, finding it to be flat across multiple wavelengths, which challenges previous models suggesting a minimum near 350 μm and aligns with recent observations of other molecular clouds.

Contribution

First measurement of the polarization spectrum of the Carina Nebula across 250, 350, and 500 μm, revealing a flat spectrum inconsistent with earlier ground-based findings.

Findings

The polarization spectrum is flat within ±15% across the observed wavelengths.

No evidence of a minimum near 350 μm in the polarization spectrum.

The spectrum shape is independent of dust temperature and optical depth.

Abstract

Linear polarization maps of the Carina Nebula were obtained at 250, 350, and 500 $\mu$m during the 2012 flight of the BLASTPol balloon-borne telescope. These measurements are combined with Planck 850 $\mu$m data in order to produce a submillimeter spectrum of the polarization fraction of the dust emission, averaged over the cloud. This spectrum is flat to within $\pm$15% (relative to the 350 $\mu$m polarization fraction). In particular, there is no evidence for a pronounced minimum of the spectrum near 350 $\mu$m, as suggested by previous ground-based measurements of other molecular clouds. This result of a flat polarization spectrum in Carina is consistent with recently-published BLASTPol measurements of the Vela C molecular cloud, and also agrees with a published model for an externally-illuminated, dense molecular cloud by Bethell and collaborators. The shape of the spectrum in Carina does not show any dependence on the radiative environment of the dust, as quantified by the Planck-derived dust temperature or dust optical depth at 353 GHz.