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Fig.:
The gas of the Coma galaxy cluster as it appears through the
Sunyaev-Zel'dovich Effect (colors) and in X-rays (contour lines).
Copyright: Planck image: ESA/ LFI & HFI Consortia;
ROSAT image: Max-Planck-Institut für extraterrestrische Physik;
Acknowledgment: Davide De Martin (ESA/Hubble)
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The SZE is the change of energy experienced by CMB photons as they
pass through the hot gas atmospheres of galaxy clusters on their way
to Earth. It imprints a characteristic signature on the CMB itself and
is thus a unique tool for detecting galaxy clusters, even at high
redshift. The nine frequency channels of Planck were carefully chosen
with this particular phenomenon very much in mind.
Planck discovered the SZ signal from the previously unknown
supercluster, which contains three clusters of galaxies. ESA's
XMM-Newton telescope pointed in that direction, confirmed the presence
of X-Rays from these three clusters of galaxies forming the
supercluster. The SZ-signal has possibly an additional component from
material betwen the clusters. This provides important clues about the
distribution of gas on very large cosmic scales.
Planck's primary goal is to capture the most ancient light of the
cosmos, the CMB. The satellite scans the sky in nine frequency
channels spanning the spectral range from 30 to 857 GHz. Such a broad
spectral coverage is not only critical for removing all sources of
contamination from the CMB, in order to deliver what will be the
sharpest image of the early Universe ever achieved - it also makes
Planck an excellent hunter of galaxy clusters by means of the
Sunyaev-Zel'dovich effect.
Links:
 ESA Press Release
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