Slice from the 2dF survey with the largest voids indicated. The lack of large voids at small distances is a selection effect due to the survey selection window.
I was born on the 19th of Februari 1979 in Leiden, the Netherlands. After graduating from high-school in 1997, I started studying Astrophysics in Leiden. In 2002 I worked on a project with Huub Röttgering in Leiden. I worked on my 'Afstudeerskriptie' (Master's thesis) with Christian Fendt at the AIP in Germany and then obtained my Master's Degree under the supervision of Vincent Icke in Leiden on the 21st of January 2004. After finishing my study I was invited by Rachid Ouyed to work with him for a period of four months in his group for computational astrophysics in Calgary (Canada). At the moment I am doing a PhD with Volker Müller in the Cosmology group at the AIP.
My main research interest now involves the study of the environmental dependence of galaxy evolution.
Currently I am studying the dynamics of galaxy groups, in particular the formation and evolution of Fossil Groups - isolated giant elliptical galaxies surrounded by a halo of hot X-ray emitting gas. These systems were discovered in the 90ies and were thought to represent the end-stage for groups, where the brightest, most massive group members merge together and form a single elliptical galaxy. The lack of any bright companions for these systems, seems a puzzle at first glance. We show a dynamic picure of these systems: once the brightest group members merge, the group undergoes a 'fossil stage' in which the host galaxy is isolated. Renewed infall onto the group from the surrounding environment ends this stage, after which they appear as any other group. Our simulations suggest that the fact that we find these systems at all is related to the relatively early infall of the group members and that they have consequently merged efficiently onto the host. For more details see my Publications section.
Part of my work was devoted to studying the large-scale structures using redshift-surveys like the 2 Degree Field Galaxy Redshift Survey 2dFGRS, high resolution N-body simulations, and semi-analytical models on galaxy formation in Dark Matter halos. In particular we studied the distribution of large under-dense patches within the large scale distribution - so called voids - and the properties of their galaxy population. This was done using the 2dFGRS, for which we could study their properties like morphological types, colors, and star formation. They are particularly interesting to study how trends with environment behave out to extremely under-dense regions. So far they have been studied little, and might provide additional constraints for models of galaxy evolution. Our results show clearly how voids defined by fainter galaxies tend to be larger compared to the mean intergalaxy separation than those defined by bright galaxies, i.e. faint galaxies trace the distribution of bright galaxies. We have compared our results to mock catalogs constructed from simulated galaxies coupled to a semi-analytical prescription for galaxy evolution. A good agreement of these scaling relations is found in the models when the survey selection window is taken into account. However, when we consider fainter galaxies within voids, we find that the change in early-type fraction away from the void centers, is steeper in simulated voids than in our observed sample at fixed magnitude. This is due to the high predicted abundance of early type satellite galaxies in these models. For more details see my Publications section.
Slice from the 2dF survey with the largest voids indicated. The lack of large voids at small distances is a selection effect due to the survey selection window.
The aim of the project with Huub Röttgering was to use Wide Field
Imaging to search for protoclusters at high redshifts (z~3.1). Because
these systems are just forming, they emit a large amount of characteristic
Lyman-α radiation due to cooling of the gas in the dark matter potential
and the large amount of star formation going on in these regions. We created a
set of candidate sources that was used for a follow-up program to study these
in more detail.
One of my research interests is the theory of computational
Magnetohydrodynamics (MHD) especially with the application to so-called
jets (streams of plasma around a central Young Stellar Object
or a Black Hole). These magnificent phenomena are observed throughout the Universe, and are yet poorly understood. For more on these topics,
see for example the websites of Christian Fendt or Rachid
Ouyed.
My Master's Thesis was on the structure of jets around Black Holes.
We were especially interested how the stationary jet structure would look like
for a differentially rotating jet in the general relativistic
environment (i.e. Kerr metric) of a rotating Black Hole. The aim was
to calculate a consistent stable magnetic field structure, along which the
wind-equations can be calculated which in turn provides the particle
acceleration along the jet, or polarization of the emitted radiation.
In Calgary I continued working on jets, but then in the context of Star Formation. Using the ZEUSMP code we simulated an outflow around a high-mass YSO, to constrain the lifetime of the outflow. For more details see my Publications section.
My Publications here.
My C.V. can be found here.
Some interesting links.