Polarized Far-infrared and Submillimeter Emission from Interstellar Dust

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 λ & 100 μm, 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 λ > 100 μm, but for some models in which only silicate grains are spheroidal, the linear polarization increases from about 3% at 100 μm 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. Subject headings: radiation mechanisms: thermal — dust, extinction — infrared: ISM