A new Cosmological Study Approach with a Volume Limited X-ray Cluster Sample

The application of galaxy clusters in constraining cosmological models iscurrently mostly limited by our uncertain knowledge of scaling relations ofobservables and cluster mass. Most scaling relation studies are based on Xrayflux limited samples which are biased. In AO10 we proposed to take a newapproach with a study of an unbiased volumelimited sample. From this approachand a comparison of both types of samples we will get many new insights into thecluster property statistics. All requested targets have been observed in AO10,but virgul 37 per cent of the observing time has been severly affected by flares.Since we require good data for the full sample, we are requesting thereobservation of 26 clusters for a total of 302 ks not to miss our original goal. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]