The Virgo Stellar Overdensity: Mapping the Infall of the Sagittarius Tidal Stream onto the Milky Way Disk

The recently discovered Virgo stellar over-density, which expands over\~1000deg^2 perpendicularly to the Galactic disk plane (7< Z <15 kpc, R~7 kpc),is the largest clump of tidal debris ever detected in the outer halo and islikely related with the accretion of a nearby dwarf galaxy by the Milky Way. Wecarry out N-body simulations of the Sagittarius stream to show that this giantstellar over-density is a confirmation of theoretical model predictions for theleading tail of the Sagittarius stream to cross the Milky Way plane in theSolar neighborhood. Radial velocity measurements are needed to confirm thisassociation and to further constrain the shape of the Milky Way dark matterhalo through a new generation of theoretical models. If the identification ofVirgo over-density and the Sagittarius leading arm is correct, we predicthighly negative radial velocities for the stars of Virgo over-density. Thedetection of this new portion of the Sagittarius tidal stream would representan excellent target for the on-going and future kinematic surveys and for darkmatter direct detection experiments in the proximity of the Sun.