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Chemical Abundances in the Nuclear Star Cluster of the Milky Way : Alpha-element Trends and Their Similarities with the Inner Bulge

Ryde, Nils LU orcid ; Nandakumar, Govind LU ; Schultheis, Mathias ; Kordopatis, Georges ; Matteo, Paola di ; Haywood, Misha ; Schödel, Rainer ; Nogueras-Lara, Francisco ; Rich, R. Michael and Thorsbro, Brian LU orcid , et al. (2025) In Astrophysical Journal 979(2).
Abstract

Chemical characterization of the Galactic center is essential for understanding its formation and structural evolution. Trends of alpha (α) elements, such as magnesium, silicon, and calcium, serve as powerful diagnostic tools, offering insights into star formation rates and gas-infall history. However, high extinction has previously hindered such studies. In this study, we present a detailed chemical abundance analysis of M giants in the Milky Way's nuclear star cluster (NSC), focusing on α-element trends with metallicity. High-resolution, near-infrared spectra were obtained using the Immersion GRating INfrared Spectrograph on the Gemini South telescope for nine M giants. Careful selection of spectral lines, based on a... (More)

Chemical characterization of the Galactic center is essential for understanding its formation and structural evolution. Trends of alpha (α) elements, such as magnesium, silicon, and calcium, serve as powerful diagnostic tools, offering insights into star formation rates and gas-infall history. However, high extinction has previously hindered such studies. In this study, we present a detailed chemical abundance analysis of M giants in the Milky Way's nuclear star cluster (NSC), focusing on α-element trends with metallicity. High-resolution, near-infrared spectra were obtained using the Immersion GRating INfrared Spectrograph on the Gemini South telescope for nine M giants. Careful selection of spectral lines, based on a solar-neighborhood control sample of 50 M giants, was implemented to minimize systematic uncertainties. Our findings show enhanced α-element abundances in the predominantly metal-rich NSC stars, consistent with trends in the inner bulge. The NSC stars follow the high-[α/Fe] envelope seen in the solar vicinity's metal-rich population, indicating a high star formation rate. The α-element trends decrease with increasing metallicity, also at the highest metallicities. Our results suggest the NSC population likely shares a similar evolutionary history with the inner bulge, challenging the idea of a recent dominant star formation burst. This connection between the NSC and the inner-disk sequence suggests that the chemical properties of extragalactic NSCs of Milky Way-type galaxies could serve as a proxy for understanding the host galaxies’ evolutionary processes.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Astrophysical Journal
volume
979
issue
2
article number
174
publisher
American Astronomical Society
external identifiers
  • scopus:85216344902
ISSN
0004-637X
DOI
10.3847/1538-4357/ad9b2b
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025. The Author(s). Published by the American Astronomical Society.
id
dd5e6385-97e3-47a7-a636-f9a34f9f11ec
date added to LUP
2025-04-08 15:35:48
date last changed
2025-04-09 08:37:13
@article{dd5e6385-97e3-47a7-a636-f9a34f9f11ec,
  abstract     = {{<p>Chemical characterization of the Galactic center is essential for understanding its formation and structural evolution. Trends of alpha (α) elements, such as magnesium, silicon, and calcium, serve as powerful diagnostic tools, offering insights into star formation rates and gas-infall history. However, high extinction has previously hindered such studies. In this study, we present a detailed chemical abundance analysis of M giants in the Milky Way's nuclear star cluster (NSC), focusing on α-element trends with metallicity. High-resolution, near-infrared spectra were obtained using the Immersion GRating INfrared Spectrograph on the Gemini South telescope for nine M giants. Careful selection of spectral lines, based on a solar-neighborhood control sample of 50 M giants, was implemented to minimize systematic uncertainties. Our findings show enhanced α-element abundances in the predominantly metal-rich NSC stars, consistent with trends in the inner bulge. The NSC stars follow the high-[α/Fe] envelope seen in the solar vicinity's metal-rich population, indicating a high star formation rate. The α-element trends decrease with increasing metallicity, also at the highest metallicities. Our results suggest the NSC population likely shares a similar evolutionary history with the inner bulge, challenging the idea of a recent dominant star formation burst. This connection between the NSC and the inner-disk sequence suggests that the chemical properties of extragalactic NSCs of Milky Way-type galaxies could serve as a proxy for understanding the host galaxies’ evolutionary processes.</p>}},
  author       = {{Ryde, Nils and Nandakumar, Govind and Schultheis, Mathias and Kordopatis, Georges and Matteo, Paola di and Haywood, Misha and Schödel, Rainer and Nogueras-Lara, Francisco and Rich, R. Michael and Thorsbro, Brian and Mace, Gregory N. and Agertz, Oscar and Amarsi, Anish M. and Kocher, Jessica and Molero, Marta and Orglia, Livia and Pagnini, Giulia and Spitoni, Emanuele}},
  issn         = {{0004-637X}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{2}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{Chemical Abundances in the Nuclear Star Cluster of the Milky Way : Alpha-element Trends and Their Similarities with the Inner Bulge}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/ad9b2b}},
  doi          = {{10.3847/1538-4357/ad9b2b}},
  volume       = {{979}},
  year         = {{2025}},
}