Issue |
A&A
Volume 439, Number 3, September I 2005
|
|
---|---|---|
Page(s) | 901 - 912 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20040322 | |
Published online | 12 August 2005 |
Trouble for cluster parameter estimation from blind SZ surveys?
1
IAS – CNRS, Bâtiment 121, Université Paris Sud, 91405 Orsay, France e-mail: aghanim@ias.u-psud.fr
2
University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Received:
24
February
2004
Accepted:
9
March
2005
The Sunyaev-Zel'dovich (SZ) effect of galaxy clusters is a
tool to measure three quantities: Compton parameter, electron
temperature, and cluster peculiar velocity. However, a major
problem is non-removed contamination by astrophysical sources that
emit in the SZ frequencies. This includes interstellar dust emission,
infra-red (IR) galaxies, and radio sources in addition to primary
Cosmic Microwave Background (CMB) anisotropies. The three former
contaminations induce systematic shifts in the three SZ
parameters. In this study, we carefully estimated, both for a
large beam experiment (namely Planck Surveyor) and a small beam
experiment (ACT-like), the systematic errors that result if a fraction
of the expected levels of emission from dust, IR galaxies, and radio
sources remains non-removed. We found that the interstellar dust
emission is not a major contaminant for the SZ measurement.
Unfortunately, the IR and radio source-induced systematic errors may
be extremely large. In particular the intra-cluster temperature
and peculiar velocity will be determined inaccurately for Planck
and ACT-like experiments, if only the frequency dependences are used
for the cleaning. The Compton parameter is also affected by the
astrophysical contaminations. The systematic errors in this case were a
factor of 2 to 5 times larger than the expected statistical error-bar
for Planck. For the ACT-like experiment, the statistical error-bars
were larger than in the case of Planck by a factor of about 5, and
therefore the systematic shifts remain within about of the
statistical errors. We have thus shown that the systematic
errors due to contaminating astrophysical emissions can be
significantly larger than the statistical errors, which implies that
future SZ surveys aiming at measuring cluster temperatures and
peculiar velocities will not be able to do so on their own without
including additional information like cluster shapes or follow-up
observations.
Key words: cosmology: cosmic microwave background / galaxies: cluster: general
© ESO, 2005
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