期刊
ASTRONOMY & ASTROPHYSICS
卷 576, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201525865
关键词
Galaxy: abundances; Galaxy: disk; Galaxy: formation; Galaxy: stellar content; stars: fundamental parameters; asteroseismology
资金
- CNPq-Brazil
- PRIN INAF
- Belspo
- NASA [NNX12AE17G]
- Physics Frontier Center/JINA
- Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE) - US National Science Foundation
- European Research Council under the European Community [338251]
- Ministerio de Ciencia e Tecnologia (MCT)
- Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ)
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)
- Financiadora de Estudos e Projetos (FINEP)
- Alfred P. Sloan Foundation
- National Science Foundation
- US Department of Energy Office of Science
- University of Arizona
- Brazilian Participation Group
- Brookhaven National Laboratory
- Carnegie Mellon University
- University of Florida
- French Participation Group
- German Participation Group
- Harvard University
- Instituto de Astrofisica de Canarias
- Michigan State/Notre Dame/JINA Participation Group
- Johns Hopkins University
- Lawrence Berkeley National Laboratory
- Max Planck Institute for Astrophysics
- Max Planck Institute for Extraterrestrial Physics
- New Mexico State University
- New York University
- Ohio State University
- Pennsylvania State University
- University of Portsmouth
- Princeton University
- Spanish Participation Group
- University of Tokyo
- University of Utah
- Vanderbilt University
- University of Virginia
- University of Washington
- Yale University
- [PHY 08-22648]
- [PHY 14-30152]
- STFC [ST/M00077X/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/M000966/1, ST/M00077X/1] Funding Source: researchfish
- Direct For Mathematical & Physical Scien
- Division Of Physics [1430152] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1109612] Funding Source: National Science Foundation
We report the discovery of a group of apparently young CoRoT red-giant stars exhibiting enhanced [alpha/Fe] abundance ratios (as determined from APOGEE spectra) with respect to solar values. Their existence is not explained by standard chemical evolution models of the Milky Way, and shows that the chemical-enrichment history of the Galactic disc is more complex. We find similar stars in previously published samples for which isochrone-ages could be reliably obtained, although in smaller relative numbers. This might explain why these stars have not previously received attention. The young [alpha/Fe]-rich stars are much more numerous in the CoRoT-APOGEE (CoRoGEE) inner-field sample than in any other high-resolution sample available at present because only CoRoGEE can explore the inner-disc regions and provide ages for its field stars. The kinematic properties of the young [alpha/Fe]-rich stars are not clearly thick-disc like, despite their rather large distances from the Galactic mid-plane. Our tentative interpretation of these and previous intriguing observations in the Milky Way is that these stars were formed close to the end of the Galactic bar, near corotation - a region where gas can be kept inert for longer times than in other regions that are more frequently shocked by the passage of spiral arms. Moreover, this is where the mass return from older inner-disc stellar generations is expected to be highest (according to an inside-out disc-formation scenario), which additionally dilutes the in-situ gas. Other possibilities to explain these observations (e.g., a recent gas-accretion event) are also discussed.
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