Polarized Microwave Radiation from Dust

Abstract

Observations of cosmic microwave background in the range 10-90 GHz have revealed an anomalous foreground component well correlated with 12 μm, 60 μm and 100 μm emission from interstellar dust. As the recent cross-correlation analysis of WHAM Hα maps with the Tenerife 10 and 15 GHz maps supports an earlier conclusion that the emission does not arise from free-free radiation, the interstellar dust origin of it is left as the only suspect. Two competing models of this emission exist. The more favored at the moment is the spinning dust model, the other is the model that uses grains with strong magnetic response. In the spinning dust model the emission arises from rapid rotation of ultrasmall grains that have dipole moments, while in the other model magnetic grains emit due to thermal vibrations of magnetic dipoles. Both models predict the emission to be partially polarized and this emission can seriously interfere with the CMB polarization measurements. We discuss observational signatures that can be used to distinguish and eventually filter out the polarized component of the microwave dust radiation.