To determine the nature of the recently discovered , ring-like stellar structure at the Galactic anticenter , we have collected spectra of a set of presumed constituent M giants selected from the 2MASS point source catalog .
Radial velocities have been obtained for stars spanning \sim 100 \arcdeg , exhibiting a trend in velocity with Galactic longitude and an estimated dispersion of \sigma _ { v } = 20 \pm 4 km s ^ { -1 } .
A mean metallicity [ Fe/H ] = -0.4 \pm 0.3 measured for these stars combines with previous evidence from the literature to suggest a population with a significant metallicity spread .
In addition , a curious alignment of at least four globular clusters of lower mean metallicity is noted to be spatially and kinematically consistent with this stellar distribution .
We interpret the M giant sample position and velocity variation with Galactic longitude as suggestive of a satellite galaxy currently undergoing tidal disruption in a non-circular , prograde orbit about the Milky Way .