Gamma radiation from the galactic center: dark matter annihilation or more conservative models?

The existence of dark matter (DM) at scales of few pc down to similar or equal to 10(-5) pc around the centers of galaxies and in particular in the Galactic Center region has been considered in the literature. Under the assumption that such a DM clump, principally constituted by non-baxyonic matter (like WIMPs) does exist at the center of our galaxy, the study of the gamma-ray emission from the Galactic Center region allows us to constrain both the mass and the size of this DM sphere. Further constraints on the DM distribution parameters may be derived by observations of bright infrared stars around the Galactic Center. Here, we discuss the constraints that can be obtained with the orbit analysis of stars (as S2 and S16) moving inside the DM concentration with present and next generations of large telescopes. In particular, consideration of the S2 star apoastron shift may allow improving limits on the DM mass and size. Further technological progress in a star orbit reconstruction and apocenter shift could detect features of bulk matter distributions or put so strict constraints on bulk mass matter (including DM) distributions that it will be impossible to explain gamma-flux with DM annihilation