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The First Chemical Census of the Milky Way’s Nuclear Star Cluster

Nandakumar, Govind LU ; Ryde, Nils LU orcid ; Schultheis, Mathias ; Rich, R. Michael ; di Matteo, Paola ; Thorsbro, Brian LU orcid and Mace, Gregory (2025) In Astrophysical Journal Letters 982(1).
Abstract

An important step in understanding the formation and evolution of the nuclear star cluster (NSC) is to investigate its chemistry and chemical evolution. Additionally, exploring the NSC’s relationship to the other structures in the Galactic center and the Milky Way disks is of great interest. Extreme optical extinction has previously prevented optical studies, but near-IR high-resolution spectroscopy is now possible. Here, we present a detailed chemical abundance analysis of 19 elements—more than 4 times as many as previously published—for nine stars in the NSC of the Milky Way, observed with the Immersion GRating INfrared Spectrometer on the Gemini South telescope. This study provides new, crucial observational evidence to shed light on... (More)

An important step in understanding the formation and evolution of the nuclear star cluster (NSC) is to investigate its chemistry and chemical evolution. Additionally, exploring the NSC’s relationship to the other structures in the Galactic center and the Milky Way disks is of great interest. Extreme optical extinction has previously prevented optical studies, but near-IR high-resolution spectroscopy is now possible. Here, we present a detailed chemical abundance analysis of 19 elements—more than 4 times as many as previously published—for nine stars in the NSC of the Milky Way, observed with the Immersion GRating INfrared Spectrometer on the Gemini South telescope. This study provides new, crucial observational evidence to shed light on the origin of the NSC. We demonstrate that it is possible to probe a variety of nucleosynthetic channels, reflecting different chemical evolution timescales. Our findings reveal that the NSC trends for the elements F, Mg, Al, Si, S, K, Ca, Ti, Cr, Mn, Co, Ni, Cu, and Zn, as well as for the s-process elements Ba, Ce, Nd, and Yb, generally follow the inner-bulge trends within uncertainties. This suggests a likely shared evolutionary history, and our results indicate that the NSC population is consistent with the chemical sequence observed in the inner Galaxy (the inner-disk sequence). However, we identify a significant and unexplained difference in the form of higher Na abundances in the NSC compared to the inner bulge. This is also observed in few Galactic globular clusters and may suggest a common enrichment process at work in all these systems.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Astrophysical Journal Letters
volume
982
issue
1
article number
L14
publisher
IOP Publishing
external identifiers
  • scopus:105000397634
ISSN
2041-8205
DOI
10.3847/2041-8213/adbb6d
language
English
LU publication?
yes
id
2950ff73-f083-405a-9633-3a06976cd90d
date added to LUP
2026-01-09 12:53:31
date last changed
2026-01-09 12:54:01
@article{2950ff73-f083-405a-9633-3a06976cd90d,
  abstract     = {{<p>An important step in understanding the formation and evolution of the nuclear star cluster (NSC) is to investigate its chemistry and chemical evolution. Additionally, exploring the NSC’s relationship to the other structures in the Galactic center and the Milky Way disks is of great interest. Extreme optical extinction has previously prevented optical studies, but near-IR high-resolution spectroscopy is now possible. Here, we present a detailed chemical abundance analysis of 19 elements—more than 4 times as many as previously published—for nine stars in the NSC of the Milky Way, observed with the Immersion GRating INfrared Spectrometer on the Gemini South telescope. This study provides new, crucial observational evidence to shed light on the origin of the NSC. We demonstrate that it is possible to probe a variety of nucleosynthetic channels, reflecting different chemical evolution timescales. Our findings reveal that the NSC trends for the elements F, Mg, Al, Si, S, K, Ca, Ti, Cr, Mn, Co, Ni, Cu, and Zn, as well as for the s-process elements Ba, Ce, Nd, and Yb, generally follow the inner-bulge trends within uncertainties. This suggests a likely shared evolutionary history, and our results indicate that the NSC population is consistent with the chemical sequence observed in the inner Galaxy (the inner-disk sequence). However, we identify a significant and unexplained difference in the form of higher Na abundances in the NSC compared to the inner bulge. This is also observed in few Galactic globular clusters and may suggest a common enrichment process at work in all these systems.</p>}},
  author       = {{Nandakumar, Govind and Ryde, Nils and Schultheis, Mathias and Rich, R. Michael and di Matteo, Paola and Thorsbro, Brian and Mace, Gregory}},
  issn         = {{2041-8205}},
  language     = {{eng}},
  number       = {{1}},
  publisher    = {{IOP Publishing}},
  series       = {{Astrophysical Journal Letters}},
  title        = {{The First Chemical Census of the Milky Way’s Nuclear Star Cluster}},
  url          = {{http://dx.doi.org/10.3847/2041-8213/adbb6d}},
  doi          = {{10.3847/2041-8213/adbb6d}},
  volume       = {{982}},
  year         = {{2025}},
}