Mapping the Galactic Halo. V. Sagittarius Dwarf Spheroidal Tidal Debris 60° from the Main Body

As part of the Spaghetti Project Survey (SPS) we have detected aconcentration of giant stars well above expectations for a smooth halo model.The position (l~350, b~50) and distance (~50 kpc) of this concentration matchthose of the Northern over-density detected by SDSS (Yanny et al. 2000, Ivezicet al. 2000). We find additional evidence for structure at ~80 kpc in the samedirection. We present radial velocities for many of these stars, including thefirst published results from the 6.5m Magellan telescope. The radial velocitiesfor stars in these structures are in excellent agreement with models of thedynamical evolution of the Sgr dwarf tidal debris, whose center is 60 degreesaway. The metallicity of stars in these streams is lower than that of the mainbody of the Sgr dwarf, which may indicate a radial metallicity gradient priorto disruption.Comment: 10 pages, 3 figures accepted in Astrophysical Journal Letter