Halo Velocity Groups in the Pisces Overdensity
  We report spectroscopic observations with the Gemini South Telescope of 5
faint V~20 RR Lyrae stars associated with the Pisces overdensity. At a
heliocentric and galactocentric distance of ~80 kpc, this is the most distant
substructure in the Galactic halo known to date. We combined our observations
with literature data and confirmed that the substructure is composed of two
different kinematic groups. The main group contains 8 stars and has <V_{gsr}> =
50 km/s, while the second group contains four stars at a velocity of <V_{gsr}>
= -52 km/s, where V_{gsr} is the radial velocity in the galactocentric standard
of rest. The metallicity distribution of RR Lyrae stars in the Pisces
overdensity is centered on [Fe/H]=-1.5 dex and has a width of 0.3 dex. The new
data allowed us to establish that both groups are spatially extended making it
very unlikely that they are bound systems, and are more likely to be debris of
a tidally disrupted galaxy or galaxies. Due to small sky coverage, it is still
unclear whether these groups have the same or different progenitors.
