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
anomalous microwave emission that interferes with cosmic microwave background
(CMB) radiation experiments. The emerging question is to what extent this
emission component contaminates to the polarized CMB radiation. We present
constraints on polarized dust emission for the model of grain size distribution
and grain alignment that best fits to observed extinction and polarization
curves. Two stars with a prominent polarization feature at wavelength 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; whereas, 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 employed to constrain polarized spinning dust emission. We find
that the degree of polarization of spinning dust emission is about 1.6 percent
at frequency ~ 3 GHz and declines to below 0.9 percent for frequency above 20
GHz. We also predict the degree of polarization of thermal dust emission at 353
GHz to be ~ 11 percent and 14 percent for the lines of sight to the HD 197770
and HD 147933-4 stars, respectively.
