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The COMBS survey – I. Chemical origins of metal-poor stars in the Galactic bulge

Lucey, Madeline ; Hawkins, Keith ; Ness, Melissa ; Asplund, Martin ; Bensby, Thomas LU orcid ; Casagrande, Luca ; Feltzing, Sofia LU orcid ; Freeman, Kenneth C. ; Kobayashi, Chiaki and Marino, Anna F. (2019) In Monthly Notices of the Royal Astronomical Society 488(2). p.2283-2300
Abstract

Chemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H] <−1 dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for... (More)

Chemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H] <−1 dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for 22 elements using R∼ 47 000 VLT/UVES spectra and contrast their elemental properties with that of other Galactic stellar populations. We find that the elemental abundances we derive for our metal-poor bulge stars have lower overall scatter than typically found in the halo. This indicates that these stars may be a distinct population confined to the bulge. If these stars are, alternatively, part of the innermost distribution of the halo, this indicates that the halo is more chemically homogeneous at small Galactic radii than at large radii. We also find two stars whose chemistry is consistent with second-generation globular cluster stars. This paper is the first part of the Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will chemodynamically characterize the metal-poor bulge population.

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author
; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: bulge, Galaxy: evolution, Stars: abundances, Stars: Population II
in
Monthly Notices of the Royal Astronomical Society
volume
488
issue
2
pages
18 pages
publisher
Oxford University Press
external identifiers
  • scopus:85074470975
ISSN
1365-2966
DOI
10.1093/mnras/stz1847
language
English
LU publication?
yes
id
b9ac4ec4-32cc-4bec-a6a5-be89c99975f2
date added to LUP
2019-11-26 13:51:28
date last changed
2024-05-16 11:09:17
@article{b9ac4ec4-32cc-4bec-a6a5-be89c99975f2,
  abstract     = {{<p>Chemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H] &lt;−1 dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for 22 elements using R∼ 47 000 VLT/UVES spectra and contrast their elemental properties with that of other Galactic stellar populations. We find that the elemental abundances we derive for our metal-poor bulge stars have lower overall scatter than typically found in the halo. This indicates that these stars may be a distinct population confined to the bulge. If these stars are, alternatively, part of the innermost distribution of the halo, this indicates that the halo is more chemically homogeneous at small Galactic radii than at large radii. We also find two stars whose chemistry is consistent with second-generation globular cluster stars. This paper is the first part of the Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will chemodynamically characterize the metal-poor bulge population.</p>}},
  author       = {{Lucey, Madeline and Hawkins, Keith and Ness, Melissa and Asplund, Martin and Bensby, Thomas and Casagrande, Luca and Feltzing, Sofia and Freeman, Kenneth C. and Kobayashi, Chiaki and Marino, Anna F.}},
  issn         = {{1365-2966}},
  keywords     = {{Galaxy: bulge; Galaxy: evolution; Stars: abundances; Stars: Population II}},
  language     = {{eng}},
  number       = {{2}},
  pages        = {{2283--2300}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{The COMBS survey – I. Chemical origins of metal-poor stars in the Galactic bulge}},
  url          = {{http://dx.doi.org/10.1093/mnras/stz1847}},
  doi          = {{10.1093/mnras/stz1847}},
  volume       = {{488}},
  year         = {{2019}},
}