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A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster

Thorsbro, B. LU orcid ; Forsberg, R. LU ; Kordopatis, G. ; Mastrobuono-Battisti, A. LU ; Church, R. P. LU orcid ; Rich, R. M. ; Ryde, N. LU orcid ; Schultheis, M. and Nishiyama, S. (2023) In Astrophysical Journal Letters 1(L18).
Abstract

We report metallicities for three ∼Gyr-old stars in the Milky Way nuclear star cluster (NSC) using high-resolution near-infrared spectroscopy. We derive effective temperatures from a calibration with Sc line strength, which yields results in good agreement with other methods, and metallicities from spectral fits to Fe i lines. Our derived metallicities range from −1.2 < [Fe/H] < + 0.5, a span of 1.7 dex. In addition we use isochrone projection to obtain masses of 1.6-4.3 M ⊙, and ages assuming single-star evolution. The oldest of these stars is 1.5 Gyr while the youngest and most metal-rich is only 100 Myr. The wide range in metallicity poses interesting questions concerning the chemical evolution and enrichment of the... (More)

We report metallicities for three ∼Gyr-old stars in the Milky Way nuclear star cluster (NSC) using high-resolution near-infrared spectroscopy. We derive effective temperatures from a calibration with Sc line strength, which yields results in good agreement with other methods, and metallicities from spectral fits to Fe i lines. Our derived metallicities range from −1.2 < [Fe/H] < + 0.5, a span of 1.7 dex. In addition we use isochrone projection to obtain masses of 1.6-4.3 M ⊙, and ages assuming single-star evolution. The oldest of these stars is 1.5 Gyr while the youngest and most metal-rich is only 100 Myr. The wide range in metallicity poses interesting questions concerning the chemical evolution and enrichment of the NSC and adds to the evidence for the presence of a young, metal-rich population in the NSC. We suggest that the candidate intermediate-age, metal-poor ([Fe/H] = −1.2) star may be best explained as a blue straggler from an underlying old population.

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Astrophysical Journal Letters
volume
1
issue
L18
article number
L18
publisher
IOP Publishing
external identifiers
  • scopus:85177784521
ISSN
2041-8205
DOI
10.3847/2041-8213/ad08b1
language
English
LU publication?
yes
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Funding Information: B.T. acknowledges the financial support from the Wenner-Gren Foundation (WGF2022-0041). R.F. acknowledges support from the Royal Physiographic Society in Lund through the Stiftelse Walter Gyllenbergs fond and Märta och Erik Holmbergs donation as well as support from the Göran Gustafsson Foundation for Research in Natural Sciences and Medicine. N.R. acknowledges support from the Swedish Research Council, VR (project No. 621-2014-5640) and Kungl. Fysiografiska Sällskapet i Lund (Stiftelsen Walter Gyllenbergs fond and Märta och Erik Holmbergs donation). M.S. acknowledges the Programme National de Cosmologie et Galaxies (PNCG) of CNRS/INSU, France, for financial support. R.M.R. acknowledges financial support from his late father Jay Baum Rich. A.M.B. acknowledges funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 895174. R.C. acknowledges support from the Swedish Research Council, VR (project No. 2017-04217). Funding Information: The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding Information: B.T. acknowledges the financial support from the Wenner-Gren Foundation (WGF2022-0041). R.F. acknowledges support from the Royal Physiographic Society in Lund through the Stiftelse Walter Gyllenbergs fond and Märta och Erik Holmbergs donation as well as support from the Göran Gustafsson Foundation for Research in Natural Sciences and Medicine. N.R. acknowledges support from the Swedish Research Council, VR (project No. 621-2014-5640) and Kungl. Fysiografiska Sällskapet i Lund (Stiftelsen Walter Gyllenbergs fond and Märta och Erik Holmbergs donation). M.S. acknowledges the Programme National de Cosmologie et Galaxies (PNCG) of CNRS/INSU, France, for financial support. R.M.R. acknowledges financial support from his late father Jay Baum Rich. A.M.B. acknowledges funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 895174. R.C. acknowledges support from the Swedish Research Council, VR (project No. 2017-04217). Publisher Copyright: © 2023. The Author(s). Published by the American Astronomical Society.
id
301df84d-5515-49f5-84de-ab32ce447e98
date added to LUP
2024-01-02 12:50:53
date last changed
2024-04-17 12:10:34
@article{301df84d-5515-49f5-84de-ab32ce447e98,
  abstract     = {{<p>We report metallicities for three ∼Gyr-old stars in the Milky Way nuclear star cluster (NSC) using high-resolution near-infrared spectroscopy. We derive effective temperatures from a calibration with Sc line strength, which yields results in good agreement with other methods, and metallicities from spectral fits to Fe i lines. Our derived metallicities range from −1.2 &lt; [Fe/H] &lt; + 0.5, a span of 1.7 dex. In addition we use isochrone projection to obtain masses of 1.6-4.3 M <sub>⊙</sub>, and ages assuming single-star evolution. The oldest of these stars is 1.5 Gyr while the youngest and most metal-rich is only 100 Myr. The wide range in metallicity poses interesting questions concerning the chemical evolution and enrichment of the NSC and adds to the evidence for the presence of a young, metal-rich population in the NSC. We suggest that the candidate intermediate-age, metal-poor ([Fe/H] = −1.2) star may be best explained as a blue straggler from an underlying old population.</p>}},
  author       = {{Thorsbro, B. and Forsberg, R. and Kordopatis, G. and Mastrobuono-Battisti, A. and Church, R. P. and Rich, R. M. and Ryde, N. and Schultheis, M. and Nishiyama, S.}},
  issn         = {{2041-8205}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{L18}},
  publisher    = {{IOP Publishing}},
  series       = {{Astrophysical Journal Letters}},
  title        = {{A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster}},
  url          = {{http://dx.doi.org/10.3847/2041-8213/ad08b1}},
  doi          = {{10.3847/2041-8213/ad08b1}},
  volume       = {{1}},
  year         = {{2023}},
}