The Local Group in LCDM - Shapes and masses of dark halos

In this Thesis we study the properties of dark matter halos assembledin the LCDM paradigm and its substructures. The first part focuses on the geometry of the mass distribution of such objects. We find that the shapes of isolated Milky Way-like dark halos significantly deviate from the spherical symmetry and respond to the local environment, directly correlating with the way in which mass accretion takes
place. The shape and orbital structure for the satellite structures inside these halos is also analyzed in detail. In general, this objects are rounder than their more massive hosts, and exhibit clear imprints of tidal disruption in both their geometrical shapes and internal orbital structure. After this, we use the number of massive structures around the Milky Way to put constraints on the total mass of the Galactic dark matter halo. The properties of the mass distribution of the Milky Way dark matter halo are investigated further in the last chapter, where we use the stellar stream assosiated to the Sagittarius dwarf galaxy to constraint the shape of the Galactic potential. We put forward a new model that ntegrates
our knowledge about the formation of the Galactic disk, the impact of satellite galaxies on measurements of the Galactic potential, and that is finally consistent with the LCDM paradigm.