An Examination of Galactic Polarization with Application to the Planck
  TB Correlation
  Angular power spectra computed from Planck HFI 353 GHz intensity and
polarization maps produce a TB correlation that can be approximated by a power
law. Whether the observed TB correlation is an induced systematic feature or a
physical property of Galactic dust emission is of interest both for
cosmological and Galactic studies. We investigate the large angular scale E-
and B-mode morphology of microwave polarized thermal dust emission, and relate
it to physical quantities of polarization angle and polarization fraction. We
use empirical models of polarized dust to show that dust polarization angle is
a key factor in producing the TB correlation. A small sample of both simulated
and observed polarization angle maps are combined with 353 GHz intensity and
dust polarization fraction to produce a suite of maps from which we compute TB
and EB. Model realizations that produce a positive TB correlation are common
and can result from large-scale (>5 degree) structure in the polarization
angle. The TB correlation appears robust to introduction of individual
intensity, polarization angle and polarization fraction model components that
are independent of the 353 GHz observations. We conclude that the observed TB
correlation is likely the result of large-scale Galactic dust polarization
properties.
