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Nils Ryde

Nils Ryde

Professor

Nils Ryde

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

Author

  • Nils Ryde
  • Govind Nandakumar
  • Mathias Schultheis
  • Georges Kordopatis
  • Paola di Matteo
  • Misha Haywood
  • Rainer Schödel
  • Francisco Nogueras-Lara
  • R. Michael Rich
  • Brian Thorsbro
  • Gregory N. Mace
  • Oscar Agertz
  • Anish M. Amarsi
  • Jessica Kocher
  • Marta Molero
  • Livia Orglia
  • Giulia Pagnini
  • Emanuele Spitoni
Show all

Summary, in English

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.

Department/s

  • Astrophysics
  • eSSENCE: The e-Science Collaboration

Publishing year

2025-02-01

Language

English

Publication/Series

Astrophysical Journal

Volume

979

Issue

2

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Astronomy, Astrophysics and Cosmology
  • Atom and Molecular Physics and Optics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-637X