Mapping the Stellar Dynamics of M31
  Using the Planetary Nebula Spectrograph, we have observed and measured the velocities for some 2764 PNe in the disk and halo of the Andromeda galaxy. Preliminary analysis using a basic ring model shows a rotation curve in good agreement with that obtained from HI data out to ~20kpc. Some substructure has also been detected within the velocity field, which can be modeled as the continuation of the tidal-remnant known as the Southern Stream, as it passes through Andromeda's disk. 
Helen Merrett, M.Merrifield, K.Kuijken, A.Romanowsky, N.Douglas,   N.Napolitano, M.Arnaboldi, M.Capaccioli, K.Freeman, O.Ger...