The following document lists the file abstract/PANDREAN_SZ.abs
from catalogue VI/111.
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A ground-based observing campaign was devoted to the search for the Sunyaev- Zeldovich (SZ) effect towards X-ray ROSAT Clusters in the millimetric spectral domain. A double-channel photometer, explicitly built to search for this effect simultaneously at two wavelengths around the peak of the Cosmic Background Radiation spectrum (1.2 and 2 mm), was adapted at the focus of the SEST antenna and observed a few objects selected from the ROSAT Survey. Both the positive (1.2 mm) and the negative signal (2 mm) were detected towards the Cluster RXJ0658-5557. A signal at 1.2mm was also found for A2744. For the FIRST time there is a strong evidence for this important cosmological effect because both the enhancement and the decrement were detected on the SAME source. In order to assess the reliability of our findings further investigations of the nature of the detected signals mainly in the FIR and radio domains are mandatory. From optical pictures of the clusters it appears that the position of the X-ray emission, which was pointed with our instrument, does not correspond to any optical source. Are there other kinds of sources ? ISO offers the 'unique' opportunity to check this question because the only way to disentangle a source signal from that due to the SZ itself is represented by observations in the FIR domain where the SZ signal is negligible. In fact at all other wavelengths of interest (i.e. those available from the ground, 850um, 750um and at lambda>3mm) the SZ signal is either stronger or negative. A complementary aim of this work is to address issues to the question of the presence of cold dust in the intracluster medium. At present this point is not settled from observations and also theoretically it is not yet clear how dust can survive in extreme hot environments such as those of cluster centers. We therefore propose to map with ISO-PHOT three clusters A2744, RXJ0658-5557 and RXJ1347-1145, which are very good candidates from our mm observations and very strong ROSAT and ASCA sources. Note that even a null result will be extremely important because it will confirm the FIRST detection of the 'positive' signal of the SZ effect and will have important consequences on the presence of dust in intracluster media.