Cosmology with galaxy clusters

Clusters of galaxies are extremely sensitive to the underlying cosmology. In this project, this sensitivity will be exploited in two different ways: 1. The abundances of clusters: A significant large new data set of massive galaxy clusters from the ESA Planck mission will be exploited to derive new constraints on the evolution of cosmic structure as a function of redshift and on the cosmological parameters that govern this evolution. Since the Planck data do not carry any information about the distance s to these clusters, a large effort of follow-up observations using optical ground-based telescopes will be undertaken to secure reliable photometric or spectroscopic redshift data for all the clusters. Combined with additional follow-up weak gravitationa l lensing and X-ray observations, the scaling relations between cluster mass and baryonic observables will be derived, allowing the Planck cluster sample to be used for cosmological constraints. 2. The detailed structure of clusters: From detaile d strong and weak gravitational lensing measurements, the mass distribution can be derived for a set of clusters. Similar constraints on the mass distribution will be derived from simulated gravitational lensing observations of galaxy clusters based on N -body simulations in a range of alternative dark energy models. These models will then be tested by confronting the observations with the simulated lensing data.