Needlet thresholding methods in component separation
  Foreground components in the Cosmic Microwave Background (CMB) are sparse in
a needlet representation, due to their specific morphological features
(anisotropy, non-Gaussianity). This leads to the possibility of applying
needlet thresholding procedures as a component separation tool. In this work,
we develop algorithms based on different needlet-thresholding schemes and use
them as extensions of existing, well-known component separation techniques,
namely ILC and template-fitting. We test soft- and hard-thresholding schemes,
using different procedures to set the optimal threshold level. We find that
thresholding can be useful as a denoising tool for internal templates in
experiments with few frequency channels, in conditions of low signal-to-noise.
We also compare our method with other denoising techniques, showing that
thresholding achieves the best performance in terms of reconstruction accuracy
and data compression while preserving the map resolution. The best results in
our tests are in particular obtained when considering template-fitting in an
LSPE like experiment, especially for B-mode spectra.
