About Me


My main research interests are in observational cosmology. As we are entering the era of “precision cosmology”, our understanding of the major constituents of the universe are limited at best: the recent discovery that the expansion of the universe is accelerating due to an unknown field dubbed the “dark energy”, is arguably the most significant finding in cosmology of the last three decades. In addition, evidence for dark matter as another dominant component is overwhelming. Making sense of this rather unexpected universe is the focus of my research and the main aim is to make accurate measurements that help constrain and test theoretical models of dark matter and dark energy.

To do so, I use a technique called weak gravitational lensing to study the dark matter distribution in the universe. This relatively new technique uses the fact that intervening structures perturb the paths of photons emitted by distant galaxies: it is as if we are viewing these galaxies through a piece of glass with a spatially varying index of refraction. As a result the images of the galaxies appear slightly distorted, which allows us to map the distribution of dark matter directly! We can use these results to study the large scale mass distribution in the universe statistically, which is a powerful probe of cosmological parameters. We can also study massive objects such as clusters of galaxies or look at the properties of galaxies. What these projects have in common is that they require large amounts of (wide-field) imaging data, which are subsequently analysed to extract the tiny weak lensing signal. These data are not only used for lensing projects, but are also the starting point of various other studies.

My research is supported by the following institutions and funding agencies:

  Euclid KiDS  
  Leiden University ERC NWO NOVA CIFAR