The Biggest Splash
  Using a large sample of bright nearby stars with accurate Gaia Data Release 2
astrometry and auxiliary spectroscopy we map out the properties of the
principle Galactic components such as the "thin" and "thick" discs and the
halo. We show that in the Solar neighborhood, there exists a large population
of metal-rich ([Fe/H]>-0.7) stars on highly eccentric orbits. By studying the
evolution of elemental abundances, kinematics and stellar ages in the plane of
azimuthal velocity v_phi and metallicity [Fe/H], we demonstrate that this
metal-rich halo-like component, which we dub the Splash, is linked to the
alpha-rich (or "thick") disc. Splash stars have little to no angular momentum
and many are on retrograde orbits. They are predominantly old, but not as old
as the stars deposited into the Milky Way in the last major merger. We argue,
in agreement with several recent studies, that the Splash stars may have been
born in the Milky Way's proto-disc prior to the massive ancient accretion event
which drastically altered their orbits. We can not, however, rule out other
(alternative) formation channels. Taking advantage of the causal connection
between the merger and the Splash, we put constraints of the epoch of the last
massive accretion event to have finished 9.5 Gyr ago. The link between the
local metal-rich and metal-poor retrograde stars is confirmed using a large
suite of cutting-edge numerical simulations of the Milky Way's formation.
