New Signatures of the Milky Way Formation in the Local Halo and Inner
  Halo Streamers in the Era of Gaia
  We explore the vicinity of the Milky Way through the use of
spectro-photometric data from the Sloan Digital Sky Survey and high-quality
proper motions derived from multi-epoch positions extracted from the Guide Star
Catalogue II database. In order to identify and characterise streams as relics
of the Milky Way formation, we start with classifying, select, and study $2417$
subdwarfs with $\rm{[Fe/H] < -1.5}$ up to $3$ kpc away from the Sun as tracers
of the local halo system. Then, through phase-space analysis, we find
statistical evidence of five discrete kinematic overdensities among $67$ of the
fastest-moving stars, and compare them to high-resolution N-body simulations of
the interaction between a Milky-Way like galaxy and orbiting dwarf galaxies
with four representative cases of merging histories. The observed overdensities
can be interpreted as fossil substructures consisting of streamers torn from
their progenitors, such progenitors appear to be satellites on prograde and
retrograde orbits on different inclinations. In particular, of the five
detected overdensities, two appear to be associated, yelding twenty-one
additional main-sequence members, with the stream of Helmi et al. (1999) that
our analysis confirms on a high inclination prograde orbit. The three newly
identified kinematic groups could be associated with the retrograde streams
detected by Dinescu (2002) and Kepley et al. (2007), whatever their origin, the
progenitor(s) would be on retrograde orbit(s) and inclination(s) within the
range $10^{\circ} \div 60^{\circ}$. Finally, we use our simulations to
investigate the impact of observational errors and compare the current picture
to the promising prospect of highly improved data expected from the Gaia
mission.
