TriAnd and its Siblings: Satellites of Satellites in the Milky Way Halo
  We explore the Triangulum-Andromeda (TriAnd) overdensity in the SPLASH
(Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo) and SEGUE
(the Sloan Extension for Galactic Understanding and Exploration) spectroscopic
surveys. Milky Way main sequence turn-off stars in the SPLASH survey reveal
that the TriAnd overdensity and the recently discovered PAndAS stream (Martin
et al. 2014) share a common heliocentric distance (D ~ 20 kpc), position on the
sky, and line-of-sight velocity (V_GSR ~ 50 km/s). Similarly, A-type, giant,
and main sequence turn-off stars selected from the SEGUE survey in the vicinity
of the Segue 2 satellite show that TriAnd is prevalent in these fields, with a
velocity and distance similar to Segue 2. The coincidence of the PAndAS stream
and Segue 2 satellite in positional and velocity space to TriAnd suggests that
these substructures are all associated, and may be a fossil record of
group-infall onto the Milky Way halo. In this scenario, the Segue 2 satellite
and PAndAS stream are "satellites of satellites", and the large, metal-rich
TriAnd overdensity is the remains of the group central.
