The following document lists the file abstract/GSERRA_SZCLUST.abs
from catalogue VI/111.
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Zel'dovich and Sunyaev (1969, Sov Astron Let 6:387) predicted that the Cosmic Microwave Background at 2.7 K could be distorded when passing through the hot gas contained in galaxy clusters. The effect is potentially a very powerfull tool of observational cosmology and many attemps have been made to detect the effect (SZ effect). A few clusters have now been detected at centimeter and millimeter wavelengths (negative effect). A large fraction of these have been detected only recently, using bolometers arrays operated in the atmospheric windows with the CSO antenna (Lange et al. 1994 preprint). The PRONAOS-SPM balloon borne subm telescope, will aim at detecting the positive part of the distortion around 800 mu. This will allow to measure the peculiar velocities of clusters and help determine important cosmological parameters such as the Hubble constant. However, in this wavelength range, emission from the galaxies in the cluster are expected to be comparable or larger than the cosmological signal, and may mimic the SZ effect. Individual galaxies contributing significantly must therefore be identified, and their Submm flux be measured with sufficient accuracy to allow a precise subtraction. Due to its wide wavelength coverage and imaging capabilites, ISO will offer a unique opportunity to make these measurements toward clusters for which detection of the positive part is foreseen in the near future. We propose to observe several clusters with PHOT (90 and 180 um) and CAM (15 um). The data will allow to determine the galaxies emission and their distribution in the cluster, which are required to estimate their contribution in the SZ beam. The targets are gathered in 2 priority groups. In the 1st priority group are clusters for which a detection of the negative effect has been reported, and the measurement of the positive effect is scheduled. The second group consists in clusters selected as good candidates for trying a detection, on the basis of their X ray emitting properties.