The age-chemical abundance structure of the Galactic disc - II. alpha-dichotomy and thick disc formation
Author
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Lian, Jianhui
Author
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Thomas, Daniel
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Maraston, Claudia
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Beers, Timothy C.
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Moni Bidin, Christian
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Fernández Trincado, José G.
Author
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Garcia-Hernandez, D. A.
Author
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Lane, Richard R.
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Muñoz Vidal, Ricardo
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Nitschelm, Christian
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Roman Lopes, Alexandre
Author
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Zamora, Olga
Admission date
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2021-03-03T21:10:19Z
Available date
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2021-03-03T21:10:19Z
Publication date
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2020
Cita de ítem
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MNRAS 497, 2371–2384 (2020)
es_ES
Identifier
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10.1093/mnras/staa2078
Identifier
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https://repositorio.uchile.cl/handle/2250/178541
Abstract
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We extend our previous work on the age-chemical abundance structure of the Galactic outer disc to the inner disc (4 < r < 8 kpc) based on the SDSS/APOGEE survey. Different from the outer disc, the inner disc stars exhibit a clear bimodal distribution in the [Mg/Fe]-[Fe/H] plane. While a number of scenarios have been proposed in the literature, it remains challenging to recover this bimodal distribution with theoretical models. To this end, we present a chemical evolution model embedding a complex multiphase inner disc formation scenario that matches the observed bimodal [Mg/Fe]-[Fe/H] distribution. In this scenario, the formation of the inner disc is dominated by two main starburst episodes 6 Gyr apart with secular, low-level star formation activity in between. In our model, the first starburst occurs at early cosmic times (t similar to 1 Gyr) and the second one 6 Gyr later at a cosmic time of t similar to 7 Gyr. Both these starburst episodes are associated with gas accretion events in our model, and are quenched rapidly. The first starburst leads to the formation of the high-a sequence, and the second starburst leads to the formation of the metal-poor low-a sequence. The metal-rich low-alpha stars, instead, form during the secular evolution phase between the two bursts. Our model shows that the alpha-dichotomy originates from the rapid suppression of star formation after the first starburst. The two starburst episodes are likely to be responsible for the formation of the geometric thick disc (z > 1 kpc), with the old inner thick disc and the young outer thick disc forming during the first and the second starbursts, respectively.
es_ES
Patrocinador
dc.description.sponsorship
UK Research & Innovation (UKRI)
Science & Technology Facilities Council (STFC)
ST/N000668/1
National Science Foundation (NSF)
PHY 14-30152
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)
CONICYT FONDECYT
3180210
1170476
1170364
Becas Iberoamerica Investigador 2019, Banco Santander Chile
QUIMAL
130001
State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU)
European Commission
AYA2017-88254-P
Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT PIA/BASAL
AFB-170002
Alfred P. Sloan Foundation
United States Department of Energy (DOE)
Center for High-Performance Computing at the University of Utah