CMB lensing reconstruction in the presence of diffuse polarized
  foregrounds
  The measurement and characterization of the lensing of the cosmic microwave
background (CMB) is key goal of the current and next generation of CMB
experiments. We perform a case study of a three-channel balloon-borne CMB
experiment observing the sky at (l,b)=(250deg,-38deg) and attaining a
sensitivity of 5.25 muK-arcmin with 8' angular resolution at 150 GHz, in order
to assess whether the effect of polarized Galactic dust is expected to be a
significant contaminant to the lensing signal reconstructed using the EB
quadratic estimator. We find that for our assumed dust model, polarization
fractions of about as low as a few percent may lead to a significant dust bias
to the lensing convergence power spectrum. We investigated a parametric
component separation method, proposed by Stompor et al. (2009), as well as a
template cleaning method, for mitigating the effect of this dust bias. The
template-based method recovers unbiased convergence power spectrum in all
polarization fraction cases we considered, while for the component separation
technique we find a dust contrast regime in which the accuracy of the profile
likelihood spectral index estimate breaks down, and in which external
information on the dust frequency scaling is needed. We propose a criterion for
putting a requirement on the accuracy with which the dust spectral index must
be estimated or constrained, and demonstrate that if this requirement is met,
then the dust bias can be removed.
