CONSTRAINT ON THE POLARIZATION OF ELECTRIC DIPOLE EMISSION FROM SPINNING DUST

Planck results have revealed that the electric dipole emission from polycyclic aromatic hydrocarbons (PAHs) is the most reliable explanation for the anomalous microwave emission that interferes with cosmic microwave background (CMB) radiation experiments. The emerging question is to what extent this emission component contaminates the polarized CMB radiation. We present constraints on polarized dust emission for the model of grain-size distribution and grain alignment that best fits the observed extinction and polarization curves. Two stars with a prominent polarization feature at lambda = 2175 angstrom-HD 197770 and HD 147933-4-are chosen for our study. For HD 197770, we find that the model with aligned silicate grains plus weakly aligned PAHs can successfully reproduce the 2175 angstrom polarization feature; in contrast, for HD 147933-4, we find that the alignment of only silicate grains can account for that feature. The alignment function of PAHs for the best-fit model to the HD 197770 data is used to constrain polarized spinning dust emission. We find that the degree of polarization of spinning dust emission is about 1.6% at frequency nu approximate to 3 GHz and declines to below 0.9% for nu > 20 GHz. We also predict the degree of polarization of thermal dust emission at 353 GHz to be P-em approximate to 11% and 14% for the lines of sight to the HD 197770 and HD 147933-4 stars, respectively.