Multi-wavelength studies of the luminous and dark mass profiles of galaxy-clusters in wide-field imaging surveys

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After the recent determination of the fundamental cosmological constants, a profound understanding of the dark and luminous matter distribution in the Universe is one of the key problems in modern cosmology. Hereby, clusters of galaxies provide well-defined laboratory environments to study the mass distribution and galaxy evolution over wide ranges of matter and galaxy densities. Today’s wide-field imaging cameras offer a unique opportunity to obtain large and statistically very well understood samples of clusters, with a selection based solely on their mass properties, using their weak gravitational lensing imprint on the shape of faint (background) galaxies. With the current proposal we ask for an extension of funding for a project aiming at exploiting these unique future data sets. Galaxy clusters will be selected on already available multi-colour data sets, a joint shear- and X-ray selection will be performed on deep multi-colour images pointing towards long XMM exposures, and a comparison of the efficiency of various cluster selection techniques will be performed. The galaxy population in the differently selected clusters will be compared; in particular, we will investigate whether shear-selected clusters have a particularly high mass-to-light ratio which would reveal a bias in ‘classical’ cluster selection methods. In addition, we will work on several technical aspects related to the data reduction and analysis of WFI data, in particular new methods for the inhomogeneous illumination and PSF corrections; these technical issues are an essential step for the full exploitation of future survey data, well beyond weak lensing applications.