Galaxy Formations

We study the galaxy distribution on large scales with modern redshift surveys and with supercomputer simulations. Galaxy properties are changing with the cosmic time due to merging of halos and galaxies within them, and due to the aging of the stellar populations. Using cosmological simulations we are interested in an understanding of the environmental dependence of galaxy properties that become obvious in observations. We compare fully gasdynamical cosmological simulations with semianalytical models of galaxy formation.

Formation of an Elliptical Galaxy

Cosmological galaxy formation simulations including gas dynamics and star formation processes are still a challenging task. We simulate the formation of elliptical galaxies. The observed red color is explained by a combination of reheating due to a star formation burst and the ignitation of an Active Galactic Nuclei where cold gas is accreted by a massive central Black Hole. We demonstrate that this process is a self-regulating process in massive galaxies. It can switch off star formation quite fast and effectiveley. The morphology of the simulated galaxy is comparable with an observed one even without a black hole, but the central regions remains blue and bright. Only by taking into account an AGN we get a realistic model. A side effect is the effective enrichment of the intergalactic medium with metals.

Satellite galaxies

We study the orbits of satellites on galaxies and groups, the orientation of its orbits, and the effect of tidal and gasdynamical interaction. The results can be compared with observations of satellite streams and dwarf galaxies around the Milky Way, that are concentrated in a very flat structure perpendicular to the plane of the Milky Way.

Formation of an
elliptical galaxy Satellite orbit around a dark
   matter halo

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