Large-Scale Polarized Foreground Component Separation for Planck
  We use Bayesian component estimation methods to examine the prospects for
large-scale polarized map and cosmological parameter estimation with simulated
Planck data assuming simplified white noise properties. The sky signal is
parametrized as the sum of the CMB, synchrotron emission, and thermal dust
emission. The synchrotron and dust components are modelled as power-laws, with
a spatially varying spectral index for synchrotron and a uniform index for
dust. Using the Gibbs sampling technique, we estimate the linear polarisation Q
and U posterior amplitudes of the CMB, synchrotron and dust maps as well as the
two spectral indices in ~4 degree pixels. We use the recovered CMB map and its
covariance in an exact pixel likelihood algorithm to estimate the optical depth
to reionization tau, the tensor-to-scalar ratio r, and to construct conditional
likelihood slices for the EE and BB spectra. Given our foreground model, we
find sigma(tau)~0.004 for tau=0.1, sigma(r)~0.03 for a model with r=0.1, and a
95% upper limit of r<0.02 for r=0.0.
