Mapping the galactic halo. V. Sagittarius dwarf spheroidal tidal debris 60° from the main body

As part of the Spaghetti Project Survey, we have detected a concentration of giant stars well above expectations for a smooth halo model. The position (l ∼ 350°, b ∼ 50°) and distance (∼50 kpc) of this concentration match those of the northern overdensity detected by the Sloan Digital Sky Survey. We find additional evidence for structure at ∼80 kpc in the same direction. We present radial velocities for many of these stars, including the first published results from the 6.5 m Magellan telescope. The radial velocities for stars in these structures are in excellent agreement with models of the dynamical evolution of the Sagittarius dwarf tidal debris, whose center is 60° away. The metallicity of stars in these streams is lower than that of the main body of the Sgr dwarf, which may indicate a radial metallicity gradient prior to disruption.