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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 710095.0, MPI für Astronomie / Publikationen_mpia
Tracing chemical evolution over the extent of the Milky Way's disk with APOGEE red clump stars
Authors:Nidever, D. L.; Bovy, J.; Bird, J. C.; Andrews, B. H.; Hayden, M.; Holtzman, J.; Majewski, S. R.; Smith, V.; Robin, A. C.; García Pérez, A. E.; Cunha, K.; Allende Prieto, C.; Zasowski, G.; Schiavon, R. P.; Johnson, J. A.; Weinberg, D. H.; Feuillet, D.; Schneider, D. P.; Shetrone, M.; Sobeck, J.; García-Hernández, D. A.; Zamora, O.; Rix, H.-W.; Beers, T. C.; Wilson, J. C.; O'Connell, R. W.; Minchev, I.; Chiappini, C.; Anders, F.; Bizyaev, D.; Brewington, H.; Ebelke, G.; Frinchaboy, P. M.; Ge, J.; Kinemuchi, K.; Malanushenko, E.; Malanushenko, V.; Marchante, M.; Mészáros, S.; Oravetz, D.; Pan, K.; Simmons, A.; Skrutskie, M. F.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal
Issue / Number:1
Start Page:id. 38 (16 pp)
Audience:Not Specified
Abstract / Description:We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the Milky Way disk. Using a sample of &ap;10, 000 kinematically unbiased red-clump stars with ~5% distance accuracy as tracers, the [alpha/Fe] versus [Fe/H] distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate metallicities, -0.9 < [Fe/H] <-0.2, but at higher metallicities ([Fe/H] ~+0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the alpha-element abundance patterns. The described abundance pattern is found throughout the range 5 < R < 11 kpc and 0 < |Z| < 2 kpc across the Galaxy. The [alpha/Fe] trend of the high-alpha sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (~10%). Using simple galactic chemical evolution models, we derive an average star-formation efficiency (SFE) in the high-alpha sequence of ~4.5 × 10-10 yr-1, which is quite close to the nearly constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the Milky Way disk was characterized by stars that shared a similar star-formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a gas consumption timescale (SFE-1) of ~2 Gyr. Finally, while the two alpha-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring, instead, a mix of two or more populations with distinct enrichment histories.
Free Keywords:Galaxy: abundances; Galaxy: disk; Galaxy: evolution; Galaxy: stellar content; Galaxy: structure; surveys
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/796/1/38
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