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Abstract: Using a resimulation technique, we perform high-resolution cosmologicalsimulations of dry mergers in a massive galaxy cluster identified in theMillennium Run. Our initial conditions include well resolved compound galaxymodels consisting of dark matter halos and stellar bulges that are used toreplace the most massive cluster progenitor halos at redshift z=3. Byconstruction, our galaxy models obey the stellar mass-size relation initially.We demonstrate that the brightest cluster galaxy BCG evolves away from theKormendy relation as defined by the smaller mass galaxies i.e., the relationbends. As a result of the comparatively large number of mergers the BCGexperiences, its total mass-to-light ratio becomes significantly higher than intypical elliptical galaxies. We also show that the mixing processes betweendark matter and stars lead to a small but numerically robust tilt in thefundamental plane and that the BCG lies on the tilted plane. Our model isconsistent with the observed steepening of the logarithmic mass-to-lightgradient as a function of the stellar mass. Surprisingly, we find onlytentative weak distortion in the Faber-Jackson relation that depends on theaperture size, unlike expected based on studies of isolated merger simulations.This may be due to differences in the distribution of galaxy orbits, which isgiven in our approach directly by the cosmological context while it has to beassumed in isolated merger simulations, and the fact that the BCG is locateddeep in the cluster potential well.



Author: Mateusz Ruszkowski 1, Volker Springel 2 1 University of Michigan, 2 Max Planck Institute for Astrophysics, Garching

Source: https://arxiv.org/







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