Polarized Far-Infrared and Submillimeter Emission from Interstellar Dust

TL;DR

This paper models polarized far-infrared and submillimeter emission from nonspherical interstellar dust grains, showing how polarization varies with wavelength and dust composition, with implications for cosmic microwave background studies.

Contribution

It provides detailed predictions of dust polarization properties based on grain composition and shape, aiding interpretation of polarization observations.

Findings

Polarized emission exceeds 6% at wavelengths >100 microns for certain models.

Linear polarization can reach up to 15% at 1 mm in silicate-only models.

Model-dependent polarization variations can help distinguish dust compositions.

Abstract

Polarized far-infrared and submillimeter emission is calculated for models of nonspherical dust grains that are constrained to reproduce the observed wavelength-dependent extinction and polarization of starlight. For emission from regions where the magnetic field is perpendicular to the line-of-sight, the far-infrared emission is expected to have substantial linear polarization at wavelengths longer than 100 microns, but the degree of linear polarization, and its variation with wavelength, is model-dependent. Models in which the starlight polarization is produced by both amorphous silicate and graphite grains have linear polarizations between 6% and 10% at wavelengths longer than 100 microns, but for some models in which only silicate grains are spheroidal, the linear polarization increases from about 3% at 100 microns to about 15% at 1 mm. We briefly discuss the implications of these results for removal of the polarized dust emission from maps of the Cosmic Microwave Background, as well as the possibility of discriminating among interstellar dust models based on observations of far-infrared and submillimeter linear polarization.