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Dark matter, galaxy orbits and scaling relations in galaxy clusters – Gary A. Mamon (Institut d’Astrophysique de Paris)
10 de julho de 2019: 12:30 - 13:30
Galaxy clusters are the most passive bound systems in the Universe. They have long been known to be dominated by dark matter. Their huge sizes suggest that the complex astrophysics of baryons, in particular gas dissipation and feedback from black holes and exploding stars, are relatively unimportant, so clusters are useful to test the predictions of the standard cosmological model. Indeed, cosmological N-body simulations of dissipationless particles predict “NFW” density profiles, with concentration varying little with mass, with velocity anisotropy increasing from isotropic to fairly radial. They also predict 2 scaling relations: a power-law pseudo phase-space density profile and a linear relation between velocity anisotropy and the logarithmic slope of the density profile. It is not clear whether these properties and relations hold for the real Universe with dissipative gas and feedback. The orbital shapes of galaxies of different morphological types are useful tracers of the assembly history of clusters and the evolution of galaxies therein. I will show how to measure jointly the distribution of total mass (mainly dark matter) and the orbital shapes of galaxies in quasi-spherical clusters and I will present the results obtained with the Bayesian MAMPOSSt method applied to a single massive cluster and to a stack of 54 regular clusters. These analyses allow to test the NFW model, show differences in the orbits of elliptical, spiral and S0 galaxies, and test whether the 2 scaling relations hold better for the total density profile or for those of the different galaxy systems.