The Biggest Splash
Vasily Belokurov, Jason L. Sanders, Azadeh Fattahi, Martin C. Smith,, Alis J. Deason, N. Wyn Evans, Robert J. J. Grand

TL;DR
This study uses Gaia data to identify a metal-rich, eccentric, retrograde stellar component called the Splash, linked to the Milky Way's ancient merger, revealing insights into galaxy formation and evolution.
Contribution
It introduces the Splash as a new stellar component associated with the Milky Way's last major accretion event, based on detailed kinematic and chemical analysis.
Findings
Identification of a metal-rich, eccentric, retrograde stellar population.
The Splash is linked to the thick disc and formed before the last major merger.
Constraints on the timing of the last massive accretion event to about 9.5 Gyr ago.
Abstract
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…
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