Marcel Zemp

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We perform a series of simulations of a Galactic mass dark matter halo at different resolutions , our largest uses over three billion particles and has a mass resolution of 1000M ⊙. We quantify the structural properties of the inner dark matter distribution and study how they depend on numerical resolution. We can measure the density profile to a distance(More)
The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at several hundred parsecs from its centre. In a cuspy CDM halo the globulars would sink to the centre from their current positions within half a billion years. We show that this timing problem is even more severe when interactions between the globular clusters are taken(More)
In cold dark matter cosmological models, structures form and grow through the merging of smaller units. Numerical simulations have shown that such merging is incomplete; the inner cores of haloes survive and orbit as 'subhaloes' within their hosts. Here we report a simulation that resolves such substructure even in the very inner regions of the Galactic(More)
We present a new time-stepping criterion for N-body simulations that is based on the true dynamical time of a particle. This allows us to follow the orbits of particles correctly in all environments since it has better adaptivity than previous time-stepping criteria used in N-body simulations. Furthermore, it requires far fewer force evaluations in low(More)
An eye movement recording experiment has been carried out to pinpoint the control of the primary attention focus. The user's attention focus is strongly influenced by dynamic processes on the screen. E.g., if a pop up menu of an appropriate size automatically appears on the static screen, then the user's attention focus changes to this new element. The(More)
The Milky Way contains several distinct old stellar components that provide a fossil record of its formation. We can understand their spatial distribution and kinematics in a hierarchical formation scenario by associating the proto-galactic fragments envisaged by Searle and Zinn (1978) with the rare peaks able to cool gas in the cold dark matter density(More)
Several general trends have been identified for equilibrated, self-gravitating collisionless systems, such as density or anisotropy profiles. These are integrated quantities which naturally depend on the underlying velocity distribution function (VDF) of the system. We study this VDF through a set of numerical simulations, which allow us to extract both the(More)
It is a clear unique prediction of the cold dark matter paradigm of cosmological structure formation that galaxies form hierarchically and are embedded in massive, extended dark halos teeming with self-bound substructure or " subhalos ". The amount and spatial distribution of subhalos around their host provide unique information and clues on the galaxy(More)