The origin of galactic disks

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The subject of this proposal focuses on the so called cosmological angular momentum problem. In numerical simulations of the formation of disk galaxies gas infalling into dark matter halos loses its angular momentum which results in disks with scale-lengths that are too small if compared to observations. We want to study if this problem arises from numerical problems connected with smooth particle hydrodynamics (SPH). In previous studies it was pointed out that in media with density contrasts the Kelvin Helmholtz instability (KHI) is completely suppressed due to an incorrect smoothing procedure. The key goal of this project is therefore to improve the SPH formalism in order to perform realistic cosmological simulations on the evolution of galaxies. The influence of the KHI will be specified in more detail based on the example of infalling cold gas clouds into large dark matter halos, that contain a hot gaseous corona. By applying cosmological simulations the question will be investigated whether an artificial suppression of the KHI causes the angular momentum problem and whether this problem can be prevented using an improved SPH algorithm.