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DETAILED ABUNDANCE ANALYSIS of A METAL-POOR GIANT in the GALACTIC CENTER

Ryde, N. LU ; Fritz, T. K.; Rich, R. M.; Thorsbro, B. LU ; Schultheis, M.; Origlia, L. and Chatzopoulos, S. (2016) In Astrophysical Journal 831(1).
Abstract

We report the first results from our program to examine the metallicity distribution of the Milky Way nuclear star cluster connected to Sgr A∗, with the goal of inferring the star formation and enrichment history of this system, as well as its connection and relationship with the central 100 pc of the bulge/bar system. We present the first high-resolution (R ∼ 24,000), detailed abundance analysis of a K = 10.2 metal-poor, alpha-enhanced red giant projected at 1.5 pc from the Galactic center, using NIRSPEC on Keck II. A careful analysis of the dynamics and color of the star locates it at about pc line-of-sight distance in front of the nuclear cluster. It probably belongs to one of the nuclear components (cluster or disk), not to the... (More)

We report the first results from our program to examine the metallicity distribution of the Milky Way nuclear star cluster connected to Sgr A∗, with the goal of inferring the star formation and enrichment history of this system, as well as its connection and relationship with the central 100 pc of the bulge/bar system. We present the first high-resolution (R ∼ 24,000), detailed abundance analysis of a K = 10.2 metal-poor, alpha-enhanced red giant projected at 1.5 pc from the Galactic center, using NIRSPEC on Keck II. A careful analysis of the dynamics and color of the star locates it at about pc line-of-sight distance in front of the nuclear cluster. It probably belongs to one of the nuclear components (cluster or disk), not to the bar/bulge or classical disk. A detailed spectroscopic synthesis, using a new line list in the K band, finds [Fe/H] ∼ -1.0 and [α/Fe] ∼ 0.4, consistent with stars of similar metallicity in the bulge. As known giants with comparable [Fe/H] and alpha enhancement are old, we conclude that this star is most likely to be a representative of the ∼10 Gyr old population. This is also the most metal-poor-confirmed red giant yet discovered in the vicinity of the nuclear cluster of the Galactic center. We consider recent reports in the literature of a surprisingly large number of metal-poor giants in the Galactic center, but the reported gravity of for these stars calls into question their reported metallicities.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: center, stars: abundances, stars: late-type
in
Astrophysical Journal
volume
831
issue
1
publisher
University of Chicago Press
external identifiers
  • scopus:84994275468
  • wos:000387229300003
ISSN
0004-637X
DOI
10.3847/0004-637X/831/1/40
language
English
LU publication?
yes
id
05b829d5-5ed4-433a-a3d2-14aca0bf6519
date added to LUP
2016-12-05 13:45:10
date last changed
2017-03-29 16:55:52
@article{05b829d5-5ed4-433a-a3d2-14aca0bf6519,
  abstract     = {<p>We report the first results from our program to examine the metallicity distribution of the Milky Way nuclear star cluster connected to Sgr A∗, with the goal of inferring the star formation and enrichment history of this system, as well as its connection and relationship with the central 100 pc of the bulge/bar system. We present the first high-resolution (R ∼ 24,000), detailed abundance analysis of a K = 10.2 metal-poor, alpha-enhanced red giant projected at 1.5 pc from the Galactic center, using NIRSPEC on Keck II. A careful analysis of the dynamics and color of the star locates it at about pc line-of-sight distance in front of the nuclear cluster. It probably belongs to one of the nuclear components (cluster or disk), not to the bar/bulge or classical disk. A detailed spectroscopic synthesis, using a new line list in the K band, finds [Fe/H] ∼ -1.0 and [α/Fe] ∼ 0.4, consistent with stars of similar metallicity in the bulge. As known giants with comparable [Fe/H] and alpha enhancement are old, we conclude that this star is most likely to be a representative of the ∼10 Gyr old population. This is also the most metal-poor-confirmed red giant yet discovered in the vicinity of the nuclear cluster of the Galactic center. We consider recent reports in the literature of a surprisingly large number of metal-poor giants in the Galactic center, but the reported gravity of for these stars calls into question their reported metallicities.</p>},
  articleno    = {40},
  author       = {Ryde, N. and Fritz, T. K. and Rich, R. M. and Thorsbro, B. and Schultheis, M. and Origlia, L. and Chatzopoulos, S.},
  issn         = {0004-637X},
  keyword      = {Galaxy: center,stars: abundances,stars: late-type},
  language     = {eng},
  month        = {11},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {DETAILED ABUNDANCE ANALYSIS of A METAL-POOR GIANT in the GALACTIC CENTER},
  url          = {http://dx.doi.org/10.3847/0004-637X/831/1/40},
  volume       = {831},
  year         = {2016},
}