Spectroscopic Signatures of Extra-Tidal Stars Around the Globular
  Clusters NGC 6656 (M22), NGC 3201 and NGC 1851 from RAVE
  Stellar population studies of globular clusters have suggested that the
brightest clusters in the Galaxy might actually be the remnant nuclei of dwarf
spheroidal galaxies. If the present Galactic globular clusters formed within
larger stellar systems, they are likely surrounded by extra-tidal halos and/or
tails made up of stars that were tidally stripped from their parent systems.
The stellar surroundings around globular clusters are therefore one of the best
places to look for the remnants of an ancient dwarf galaxy. Here an attempt is
made to search for tidal debris around the supernovae enriched globular
clusters M22 and NGC 1851 as well as the kinematically unique cluster NGC 3201.
The stellar parameters from the Radial Velocity Experiment (RAVE) are used to
identify stars with RAVE metallicities, radial velocities and
elemental-abundances consistent with the abundance patterns and properties of
the stars in M22, NGC 1851 and NGC 3201. The discovery of RAVE stars that may
be associated with M22 and NGC 1851 are reported, some of which are at
projected distances of ~10 degrees away from the core of these clusters.
Numerous RAVE stars associated with NGC 3201 suggest that either the tidal
radius of this cluster is underestimated, or that there are some unbound stars
extending a few arc minutes from the edge of the cluster's radius. No further
extra-tidal stars associated with NGC 3201 could be identified. The bright
magnitudes of the RAVE stars make them easy targets for high resolution
follow-up observations, allowing an eventual further chemical tagging to
solidify (or exclude) stars outside the tidal radius of the cluster as tidal
debris. In both our radial velocity histograms of the regions surrounding NGC
1851 and NGC 3201, a peak of stars at 230 km/s is seen, consistent with
extended tidal debris from omega Centauri.
