Using a sample of 43 bright (V<16.1, distance <13 kpc) RR Lyrae stars (RRLS)
from the QUEST survey with spectroscopic radial velocities and metallicities,
we find that several separate halo substructures contribute to the Virgo
overdensity (VOD). While there is little evidence for halo substructure in the
spatial distribution of these stars, their distribution in radial velocity
reveals two moving groups. These results are reinforced when the sample is
combined with a sample of blue horizontal branch stars that were identified in
the SDSS, and the combined sample provides evidence for one additional moving
group. These groups correspond to peaks in the radial velocity distribution of
a sample of F type main-sequence stars that was recently observed in the same
directon by SEGUE, although in one case the RRLS and F star groups may not lie
at the same distance. One of the new substructures has a very narrow range in
metallicity, which is more consistent with it being the debris from a destroyed
globular cluster than from a dwarf galaxy. A small concentration of stars have
radial velocities that are similar to the Virgo Stellar Stream (VSS) that was
identified previously in a fainter sample of RRLS. Our results suggest that
this feature extends to distances as short as ~12 kpc from its previous
detection at ~19 kpc. None of the new groups and only one star in the sample
have velocities that are consistent with membership in the leading tidal stream
from the Sagittarius Dwarf Spheroidal Galaxy, which some authors have suggested
is the origin of the VOD.Comment: Accepted for publication in the A