Robert J.J. Grand
The biggest Splash
Grand, Robert J.J.; Evans, N. Wyn; Deason, Alis J.; Smith, Martin C.; Fattahi, Azadeh; Sanders, Jason L.; Belokurov, Vasily
Authors
N. Wyn Evans
Professor Alis Deason alis.j.deason@durham.ac.uk
Professor
Martin C. Smith
Dr Azadeh Fattahi Savadjani azadeh.fattahi-savadjani@durham.ac.uk
Associate Professor
Jason L. Sanders
Vasily Belokurov
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 confirm previous claims 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 vφ and metallicity [Fe/H], we demonstrate that this metal-rich halo-like component, which we dub the Splash, is linked to the α-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.
Citation
Grand, R. J., Evans, N. W., Deason, A. J., Smith, M. C., Fattahi, A., Sanders, J. L., & Belokurov, V. (2020). The biggest Splash. Monthly Notices of the Royal Astronomical Society, 494(3), 3880-3898. https://doi.org/10.1093/mnras/staa876
Journal Article Type | Article |
---|---|
Acceptance Date | Mar 26, 2020 |
Online Publication Date | Apr 7, 2020 |
Publication Date | May 31, 2020 |
Deposit Date | Apr 8, 2020 |
Publicly Available Date | Apr 8, 2020 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Royal Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 494 |
Issue | 3 |
Pages | 3880-3898 |
DOI | https://doi.org/10.1093/mnras/staa876 |
Public URL | https://durham-repository.worktribe.com/output/1266625 |
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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s) . Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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