Our Galaxy is a prime example of a barred galaxy with a box/peanut bulge. In the last years, we have used NIR star counts to determine the three-dimensional structure of the Galactic bulge and bar. We are using N-body and Made-to-measure particle methods to study the dynamics of the Milky Way bar and bulge, and to determine the distribution of stellar mass and dark matter. We are also investigating the nuclear star cluster around the central black hole in the Galaxy. The possibility to study these components "star-by-star" makes our Milky Way an essential laboratory for understanding the evolutionary history of similar galaxies. [more]

Galaxies in a hierarchical universe are growing through accreting smaller systems. We study particularly the outer halos of massive galaxies to find signatures of this process, but also to characterize the kinematics, angular momentum, and dark matter in these halos, and to determine how they blend into their surroundings, the intracluster or intragroup light. We also host the website of the Planetary Nebula Spectrograph (PN.S) project; planetary nebulae are some of the best tracers to study the outermost regions of galaxies which are too faint for conventional spectroscopy. [more]

We have studied the spin-up of primordial bulges due to the interaction with bars, using N-body simulations to follow the growth of the bar and the formation of a box/peanut bulge. We then compared the resulting composite bulges with observations of nearby spiral galaxies and constructed dynamical models for the barred bulge of M31. We have further observed planetary nebulae in the Andromeda galaxy to image its disk and halo. [more]

With M2M methods it is possible to evolve an N-body system of particles towards a given target, which can be specified by observational data or model constraints. The technique is similar to an N-body method with variable weights (particle masses) which evolve according to the deviations between model and constraints. [more]