Component separation in CMB observations
  In these proceedings, we discuss the extraction, in WMAP 5 year data, of a
clean CMB map, of foreground emission (dominated by emission of the
interstellar medium of our galaxy), and of the tiny signal from Sunyaev
Zel'dovich effect in the direction of known galaxy clusters. The implementation
of an Internal Linear Combination method locally in both pixel and harmonic
space, with the use of a decomposition of WMAP maps onto a frame of spherical
needlets, permits to extract a full sky CMB map, with good accuracy even in
regions close to the galactic plane. Proper subtraction of this estimated CMB
from WMAP original observations provides us with CMB-free foreground maps,
which can be used for the analysis of the emission of the galactic interstellar
medium and for detecting and measuring emissions from compact sources. Finally,
while the Sunyaev-Zel'dovich cannot be detected for individual clusters in WMAP
data, due to lack of spatial resolution and sensitivity, a stacking analysis of
tentative detections towards a number of known ROSAT clusters permits to detect
the SZ effect in WMAP data and measure how the SZ flux scales with cluster mass
and X-ray luminosity.
