The dynamics of stars near Sgr A* and dark matter at the center and in the halo of the galaxy

After a discussion of the properties of degenerate fermion balls, we analyze the orbits of the star S0-1, which has the smallest projected distance to Sgr A*, in the supermassive black hole as well as in the fermion ball scenarios of the Galactic center. It is shown that both scenarios are consistent with the data, as measured during the last six years by Genzel et al. and Ghez et al. We then consider a self-gravitating ideal fermion gas at nonzero temperature as a model for the Galactic halo. The Galactic halo of mass similar to 2 x 10(12)M(circle dot) enclosed within a radius of similar to 200 kpc implies the existence of a supermassive compact dark object at the Galactic center that is in hydrostatic and thermal equilibrium with the halo. The central object has a maximal mass of similar to 2.3 x 10(6)M(circle dot) within a minimal radius of similar to 18 mpc or similar to 21 light-days for fermion masses similar to 15 keV. We thus conclude that both the supermassive compact dark object and the halo could be made of the same weakly interacting similar to 15 keV particle.