|Dr. Tim Schrabback||SCHEDULED|
Argelander-Institut für Astronomie, Bonn
The Universe appears to be dominated by dark matter (driving the growth of structure) and dark energy (driving the late-time accelerated expansion). Together, these invisible components contribute to 95% of the cosmic energy budget. Yet, their physical nature is still unclear. A powerful tool to learn more about them is weak gravitational lensing: The light bundles of background galaxies get distorted while passing through the gravitational potential of foreground matter concentrations. These distortions can be measured statistically, allowing us to reconstruct the foreground mass distribution, weigh cosmological objects, and probe the cosmological growth of structure. In this talk I will summarise several observational studies, in which we employed weak lensing measurements aiming to test and constrain the cosmological model. This includes stacked measurements of the weak lensing signal around large samples of foreground galaxies, where we search for the expected signature of dark matter halo flattening. Weak lensing is also an essential ingredient for cosmological investigations based on the number counts of galaxy clusters, since it allows us to robustly constrain their absolute mass scale. In this context I will present results based on our weak lensing follow-up campaign for clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey. Finally, the statistics of the large-scale matter distribution can also be probed by correlating the distorted shapes of background galaxy pairs in high-resolution wide-area imaging surveys. As an example for such cosmological weak lensing measurements I will present some of our earlier results obtained using Hubble Space Telescope imaging, followed by an outlook into what will be possible with ESA's upcoming Euclid mission.