A minimal power-spectrum-based moment expansion for CMB B-mode searches

Understand

The characterization and modeling of polarized foregrounds has become a critical issue in the quest for primordial $B$-modes.

• A typical method to proceed is to factorize and parametrize the spectral properties of foregrounds and their scale dependence (i.e.
• assuming that foreground spectra are well described everywhere by their sky average).
• Since in reality foreground properties vary across the Galaxy, this assumption leads to inaccuracies in the model that manifest themselves as biases in the final cosmological parameters (in this case the tensor-to-scalar ratio $r$).