According to Einstein's theory of general relativity the light of an object is deflected by a mass in its foreground. The deflections can be very weak or so strong that they are visible by eye... Show moreAccording to Einstein's theory of general relativity the light of an object is deflected by a mass in its foreground. The deflections can be very weak or so strong that they are visible by eye yielding strangely distorted arcs or even multiple images of the same source. Measurements of strong or weak lensing let us infer the total mass of the light-deflecting object which is an important cosmological observable. In this thesis we employ gravitational lensing to measure key cosmological observables, such as dark matter and dark energy. Instead of observing the effects of gravitational lensing around single galaxies or galaxy clusters, the Universe itself can be used as a lens: light travelling to us through the cosmic large-scale structure is also weakly lensed by it. Measuring this effect at different cosmic times allows us to infer the evolution of structure in the cosmic web. Hence, we can study how that is affected by dark energy or massive neutrinos. A key result of this thesis is that we find a lower amplitude for the clustering of matter at fixed matter density than that inferred from the most recent measurements of the cosmic microwave background radiation by the Planck satellite. Show less
Galaxy clusters are the largest reservoirs of matter in the Universe, and as such are unique laboratories to understand the connection between dark and luminous, 'normal' matter. We use... Show more Galaxy clusters are the largest reservoirs of matter in the Universe, and as such are unique laboratories to understand the connection between dark and luminous, 'normal' matter. We use several techniques and galaxy cluster samples to study this connection from various angles. In particular, we try to understand how does the motion of galaxies within clusters relate to their luminous mass content; how do the shapes of galaxies respond to the strong gravitational potential of their host cluster (analogous to tidal waves produced by the Earth-Moon gravitational interaction), and how much of their total mass are galaxies able to retain once they fall under the influence of their host cluster, in connection with the same interactions. Our results provide important information for models of galaxy formation and evolution, particularly their dark matter content, and for studies trying to link observations of galaxy clusters to the overall properties of the Universe such as its total matter content. Show less
