Optical and X-ray properties of galaxy clusters
Galaxy clusters are very useful astronomical tools; they are used as a means to study galaxy formation and evolution, large scale structure, but also as probes to constrain cosmological parameters. This work aims to explore some of the uses of galaxy clusters in cosmology by constructing an optically confirmed X-ray selected galaxy cluster catalogue and studying various aspects of galaxy clusters and their effect on cosmology. I introduce the theoretical background of this work, describing the current cosmological model, the properties, dynamics and use of galaxy clusters. I describe the main tools that were used to create the XMM Cluster Survey (XCS) DR2 cluster catalogue in the SDSS region and proceed with a thorough outline of the construction and properties of the clusters in the catalogue. The properties of these clusters, along with clusters from optical catalogues and clusters from simulations were studied further as a function of their environment. Possible differences in the properties, mass functions and luminosity-temperature relation of clusters in different environments show the influence of the latter on the formation and growth of galaxy clusters. Moreover, those differences can affect the results of cosmological studies that do not take into account this environmental selection effect. Finally, I study the rotation of the constituents of the galaxy clusters. Rotating cluster galaxy members can change the result of the calculation of the virial mass of the galaxy clusters that is used in many types of studies, amongst which is cosmology. A comparison of the rotation of the different constituents of the clusters give insight on their formation and the processes happening during their lifetime. I close with the conclusions of the studies of galaxy clusters and the future prospects of this work.