Submillimeter Polarization Spectrum in the Vela C Molecular Cloud

TL;DR

This study presents polarization measurements of the Vela C molecular cloud across multiple submillimeter wavelengths, revealing a flat polarization spectrum unaffected by local radiative conditions, supporting a model of a porous, uniformly heated cloud.

Contribution

First detailed polarization spectrum of Vela C across 250-850um, showing a flat profile and consistent with a porous, clumpy cloud model.

Findings

Polarization spectrum is relatively flat across observed wavelengths.

Spectrum does not show a minimum at 350um as in other clouds.

Polarization ratios align with a model of a porous, uniformly heated cloud.

Abstract

Polarization maps of the Vela C molecular cloud were obtained at 250, 350, and 500um during the 2012 flight of the balloon-borne telescope BLASTPol. These measurements are used in conjunction with 850um data from Planck to study the submillimeter spectrum of the polarization fraction for this cloud. The spectrum is relatively flat and does not exhibit a pronounced minimum at \lambda ~350um as suggested by previous measurements of other molecular clouds. The shape of the spectrum does not depend strongly on the radiative environment of the dust, as quantified by the column density or the dust temperature obtained from Herschel data. The polarization ratios observed in Vela C are consistent with a model of a porous clumpy molecular cloud being uniformly heated by the interstellar radiation field.