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dc.contributor.authorBeraldo e Silva, Leandro
dc.contributor.authorDebattista, Victor P.
dc.contributor.authorNidever, David
dc.contributor.authorAmarante, João A S
dc.contributor.authorGarver, Bethany
dc.identifier.citationBeraldo e Silva, L., Debattista, V. P., Nidever, D., Amarante, J. A., & Garver, B. (2021). Co-formation of the thin and thick discs revealed by APOGEE-DR16 and Gaia-DR2. Monthly Notices of the Royal Astronomical Society, 502(1), 260-272.en_US
dc.descriptionThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society 2020 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.en_US
dc.description.abstractSince thin disc stars are younger than thick disc stars on average, the thin disc is predicted by some models to start forming after the thick disc had formed, around 10 Gyr ago. Accordingly, no significant old thin disc population should exist. Using 6D coordinates from Gaia-DR2 and age estimates from Sanders & Das, we select ∼24 000 old stars (${\tau \gt 10\mbox{$\, \mathrm{Gyr}$}}$, with uncertainties $\lesssim 15$) within $2\mbox{$\, \mathrm{kpc}$}$ from the Sun (full sample). A cross-match with APOGEE-DR16 (∼1000 stars) reveals comparable fractions of old chemically defined thin/thick disc stars. We show that the full sample pericentre radius (rper) distribution has three peaks, one associated with the stellar halo and the other two having contributions from the thin/thick discs. Using a high-resolution N-body + SPH simulation, we demonstrate that one peak, at $\mbox{$r_\mathrm{per}$}\approx 7.1\mbox{$\, \mathrm{kpc}$}$, is produced by stars from both discs that were born in the inner Galaxy and migrated to the Solar Neighbourhood. In the Solar Neighbourhood, ∼1/2 (∼1/3) of the old thin (thick) disc stars are classified as migrators. Our results suggest that thin/thick discs are affected differently by radial migration inasmuch as they have different eccentricity distributions, regardless of vertical scale heights. We interpret the existence of a significant old thin disc population as evidence for an early co-formation of thin/thick discs, arguing that clump instabilities in the early disc offer a compelling explanation for the observed trends.en_US
dc.publisherOxford University Pressen_US
dc.rightscopyrights oxford 2021en_US
dc.subjectapogee dr16en_US
dc.titleCo-formation of the thin and thick discs revealed by APOGEE-DR16 and Gaia-DR2en_US
mus.citation.journaltitleMonthly Notices of the Royal Astronomical Societyen_US
mus.relation.collegeCollege of Letters & Scienceen_US
mus.relation.universityMontana State University - Bozemanen_US

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