This section hasn't been updated for a while. Even so, the topics listed here are still part of my main research topics. The text in the description is, however, outdated and more developments have been made over the past years.
Click on the thumbnails on the right for larger, more descriptive images.
Quasar (macro) Lensing
The lensing of distant quasars allows to measure the Hubble constant. By modeling the lens mass distribution and comparing to measure time delays for the different images in a lensed quasar, it is possible to determine the Hubble Constant as well as the matter (light and dark) distribution. In order to correctly model the lens mass distribution it is very important to understand all of the objects that are affecting the lensing potential as well as to accurately understand the brightness of the lensed quasar.
It can happen that an image of a lensed quasar encounters its way another body of mass and gets re magnified again. In other words, quasar images may get additionally magnified by stars in the lensing galaxy. Due to the micro-arc second resolution action of microlensing and the relatively short time scales, quasar microlensing allows us to measure properties from the background quasar and the (micro) lensing objects. By coupling quasar microlensing light curves with microlensing computational simulations (magnification patterns), we can measure accretion disk sizes and profiles, projected velocities of the microlenses as well as masses for the microlensing object.
Even though historically galaxy-galaxy lensing is a far more common phenomenon that galaxy-quasar lensing, due to their easier detection, most of the efforts have been centered in the detection latter. Recently, however, due to the advent of large extragalactic surveys, galaxy-galaxy lenses have been actively sought for.
Large statistical samples of galaxy-galaxy lenses can provide insights on several modern astrophysical questions. For example, using a cosmological model, the configuration of the lensing induced multiple images and arcs of a background source and their relative fluxes can be used to study the mass profile of lensing galaxies and its evolution, including the measure of galactic substructure. On the other hand, the magnification induced by lensing allows the study of intrinsically faint and distant sources. Furthermore, statistical samples of strong lensing systems (arcs number density) can be used to test cosmological models.
Check out the RCS2 Galaxy Scale Lens Catalog
Restricted Access (at the moment)