New insights into foreground analysis of the WMAP five-year data using
  FASTICA
  In this paper, we present a foreground analysis of the WMAP 5-year data using
the FASTICA algorithm, improving on the treatment of the WMAP 3-year data in
Bottino et al 2008. We revisit the nature of the free-free spectrum with the
emphasis on attempting to confirm or otherwise the spectral feature claimed in
Dobbler et al 2008b and explained in terms of spinning dust emission in the
warm ionised medium. With the application of different Galactic cuts, the index
is always flatter than the canonical value of 2.14 except for the Kp0 mask
which is steeper. Irrespective of this, we can not confirm the presence of any
feature in the free-free spectrum. We experiment with a more extensive approach
to the cleaning of the data, introduced in connection with the iterative
application of FASTICA. We confirm the presence of a residual foreground whose
spatial distribution is concentrated along the Galactic plane, with pronounced
emission near the Galactic center. This is consistent with the WMAP haze
detected in Finkbeiner 2004. Finally, we attempted to perform the same analysis
on full-sky maps. The code returns good results even for those regions where
the cross-talk among the components is high. However, slightly better results
in terms of the possibility of reconstructing a full-sky CMB map, are achieved
with a simultaneous analysis of both the five WMAP maps and foreground
templates. Nonetheless, some residuals are still present and detected in terms
of an excess in the CMB power spectrum, on small angular scales. Therefore, a
minimal mask for the brightest regions of the plane is necessary, and has been
defined.
