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Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars | | David L. Nidever
; Jo Bovy
; Jonathan C. Bird
; Brett H. Andrews
; Michael Hayden
; Jon Holtzman
; Steven R. Majewski
; Verne Smith
; Annie C. Robin
; Ana E. Garcia Perez
; Katia Cunha
; Carlos Allende Prieto
; Gail Zasowski
; Ricardo P. Schiavon
; Jennifer A. Johnson
; David H. Weinberg
; Diane Feuillet
; Donald P. Schneider
; Matthew Shetrone
; Jennifer Sobeck
; D. A. Garcia-Hernandez
; O. Zamora
; Hans-Walter Rix
; Timothy C. Beers
; John C. Wilson
; Robert W. O'Connell
; Ivan Minchev
; Cristina Chiappini
; Friedrich Anders
; Dmitry Bizyaev
; Howard Brewington
; Garrett Ebelke
; Peter M. Frinchaboy
; Jian Ge
; Karen Kinemuchi
; Elena Malanushenko
; Viktor Malanushenko
; Moses Marchante
; Szabolcs Meszaros
; Daniel Oravetz
; Kaike Pan
; Audrey Simmons
; Michael F. Skrutskie
; | | Date: |
11 Sep 2014 | | Abstract: | 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 ~10,000 kinematically-unbiased red-clump
stars with ~5% distance accuracy as tracers, the [alpha/Fe] vs. [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 ~4.5E-10
1/yr, 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 (1/SFE)
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. | | Source: | arXiv, 1409.3566 | | Services: | Forum | Review | PDF | Favorites | |
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