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Principal Component Abundance Analysis of Microlensed Bulge Dwarf and Subgiant Stars

Andrews, B. H.; Weinberg, D. H.; Johnson, J. A.; Bensby, Thomas LU and Feltzing, Sofia LU (2012) In Acta Astronomica 62(3). p.269-279
Abstract
Elemental abundance patterns can provide vital clues to the formation and enrichment history of a stellar population. Here we present an investigation of the Galactic bulge, where we apply principal component abundance analysis (PCAA) - a principal component decomposition of relative abundances [X/Fe] to a sample of 35 microlensed bulge dwarf and subgiant stars, characterizing their distribution in the 12-dimensional space defined by their measured elemental abundances. The first principal component PC I, which suffices to describe the abundance patterns of most stars in the sample, shows a strong contribution from alpha-elements, reflecting the relative contributions of Type II and Type 1a supernovae. The second principal component PC2 is... (More)
Elemental abundance patterns can provide vital clues to the formation and enrichment history of a stellar population. Here we present an investigation of the Galactic bulge, where we apply principal component abundance analysis (PCAA) - a principal component decomposition of relative abundances [X/Fe] to a sample of 35 microlensed bulge dwarf and subgiant stars, characterizing their distribution in the 12-dimensional space defined by their measured elemental abundances. The first principal component PC I, which suffices to describe the abundance patterns of most stars in the sample, shows a strong contribution from alpha-elements, reflecting the relative contributions of Type II and Type 1a supernovae. The second principal component PC2 is characterized by a Na-Ni correlation, the likely product of metallicity-dependent Type II supernova yields. The distribution in PC I is bimodal, showing that the bimodality previously found in the [Fe/H] values of these stars is robustly and independently recovered by looking at only their relative abundance patterns. The two metal-rich stars that are alpha-enhanced have outlier values of PC2 and PC3, respectively, further evidence that they have distinctive enrichment histories. Applying PCAA to a sample of local thin and thick disk dwarfs yields a nearly identical PC I. In PC I, the metal-rich and metal-poor bulge dwarfs track kinematically selected thin and thick disk dwarfs, respectively, suggesting broadly similar alpha-enrichment histories. However, the disk PC2 is dominated by a Y-Ba correlation, likely indicating a contribution of s-process enrichment from long-lived asymptotic giant branch stars that is absent from the bulge PC2 because of its rapid formation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: general, Galaxy: bulge, Galaxy: evolution, Galaxy: formation, Galaxy: stellar content, Stars: abundances
in
Acta Astronomica
volume
62
issue
3
pages
269 - 279
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • wos:000310490900003
  • scopus:84869025104
ISSN
0001-5237
language
English
LU publication?
yes
id
766cd299-dbe7-485f-9f3b-04617842c7dd (old id 3284034)
date added to LUP
2012-12-20 11:05:04
date last changed
2017-02-26 03:52:21
@article{766cd299-dbe7-485f-9f3b-04617842c7dd,
  abstract     = {Elemental abundance patterns can provide vital clues to the formation and enrichment history of a stellar population. Here we present an investigation of the Galactic bulge, where we apply principal component abundance analysis (PCAA) - a principal component decomposition of relative abundances [X/Fe] to a sample of 35 microlensed bulge dwarf and subgiant stars, characterizing their distribution in the 12-dimensional space defined by their measured elemental abundances. The first principal component PC I, which suffices to describe the abundance patterns of most stars in the sample, shows a strong contribution from alpha-elements, reflecting the relative contributions of Type II and Type 1a supernovae. The second principal component PC2 is characterized by a Na-Ni correlation, the likely product of metallicity-dependent Type II supernova yields. The distribution in PC I is bimodal, showing that the bimodality previously found in the [Fe/H] values of these stars is robustly and independently recovered by looking at only their relative abundance patterns. The two metal-rich stars that are alpha-enhanced have outlier values of PC2 and PC3, respectively, further evidence that they have distinctive enrichment histories. Applying PCAA to a sample of local thin and thick disk dwarfs yields a nearly identical PC I. In PC I, the metal-rich and metal-poor bulge dwarfs track kinematically selected thin and thick disk dwarfs, respectively, suggesting broadly similar alpha-enrichment histories. However, the disk PC2 is dominated by a Y-Ba correlation, likely indicating a contribution of s-process enrichment from long-lived asymptotic giant branch stars that is absent from the bulge PC2 because of its rapid formation.},
  author       = {Andrews, B. H. and Weinberg, D. H. and Johnson, J. A. and Bensby, Thomas and Feltzing, Sofia},
  issn         = {0001-5237},
  keyword      = {Galaxy: general,Galaxy: bulge,Galaxy: evolution,Galaxy: formation,Galaxy: stellar content,Stars: abundances},
  language     = {eng},
  number       = {3},
  pages        = {269--279},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Acta Astronomica},
  title        = {Principal Component Abundance Analysis of Microlensed Bulge Dwarf and Subgiant Stars},
  volume       = {62},
  year         = {2012},
}