Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge
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. How...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9b2b |
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| 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 |
| author_facet | 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 |
| author_sort | Nils Ryde |
| collection | DOAJ |
| description | 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. |
| format | Article |
| id | doaj-art-e18139ea5cf74c50b1ddb192b4fef804 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-e18139ea5cf74c50b1ddb192b4fef8042025-08-20T03:05:04ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979217410.3847/1538-4357/ad9b2bChemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner BulgeNils Ryde0https://orcid.org/0000-0001-6294-3790Govind Nandakumar1https://orcid.org/0000-0002-6077-2059Mathias Schultheis2https://orcid.org/0000-0002-6590-1657Georges Kordopatis3https://orcid.org/0000-0002-9035-3920Paola di Matteo4Misha Haywood5Rainer Schödel6https://orcid.org/0000-0001-5404-797XFrancisco Nogueras-Lara7https://orcid.org/0000-0002-6379-7593R. Michael Rich8https://orcid.org/0000-0003-0427-8387Brian Thorsbro9https://orcid.org/0000-0002-5633-4400Gregory N. Mace10https://orcid.org/0000-0001-7875-6391Oscar Agertz11https://orcid.org/0000-0002-4287-1088Anish M. Amarsi12https://orcid.org/0000-0002-3181-3413Jessica Kocher13Marta Molero14Livia Orglia15https://orcid.org/0000-0002-6040-5849Giulia Pagnini16Emanuele Spitoni17https://orcid.org/0000-0001-9715-5727Division of Astrophysics, Department of Physics, Lund University , Box 118, SE-22100 Lund, Sweden ; nils.ryde@fysik.lu.seDivision of Astrophysics, Department of Physics, Lund University , Box 118, SE-22100 Lund, Sweden ; nils.ryde@fysik.lu.se; Aryabhatta Research Institute of Observational Sciences , Manora Peak, Nainital 263002, IndiaUniversité Côte d’Azur , Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS, Blvd de l’Observatoire, 06304 Nice, FranceUniversité Côte d’Azur , Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS, Blvd de l’Observatoire, 06304 Nice, FranceGEPI, Observatoire de Paris, PSL Research University , CNRS, Place Jules Janssen, F-92195 Meudon, FranceGEPI, Observatoire de Paris, PSL Research University , CNRS, Place Jules Janssen, F-92195 Meudon, FranceInstituto de Astrofísica de Andalucía (CSIC) , Glorieta de la Astronomía s/n, 18008 Granada, SpainEuropean Southern Observatory , Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, GermanyDepartment of Physics and Astronomy, UCLA , 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USAUniversité Côte d’Azur , Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS, Blvd de l’Observatoire, 06304 Nice, FranceDepartment of Astronomy and McDonald Observatory, The University of Texas , Austin, TX 78712, USADivision of Astrophysics, Department of Physics, Lund University , Box 118, SE-22100 Lund, Sweden ; nils.ryde@fysik.lu.seTheoretical Astrophysics, Department of Physics and Astronomy, Uppsala University , Box 516, SE-751 20 Uppsala, SwedenDivision of Astrophysics, Department of Physics, Lund University , Box 118, SE-22100 Lund, Sweden ; nils.ryde@fysik.lu.seInstitut für Kernphysik, Technische Universität Darmstadt , Schlossgartenstr. 2, Darmstadt 64289, GermanyINAF , Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, ItalyGEPI, Observatoire de Paris, PSL Research University , CNRS, Place Jules Janssen, F-92195 Meudon, FranceINAF , Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, ItalyChemical 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.https://doi.org/10.3847/1538-4357/ad9b2bGalactic centerChemical abundancesGalactic archaeologyM giant starsNear infrared astronomyHigh resolution spectroscopy |
| spellingShingle | 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 Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge The Astrophysical Journal Galactic center Chemical abundances Galactic archaeology M giant stars Near infrared astronomy High resolution spectroscopy |
| title | Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge |
| title_full | Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge |
| title_fullStr | Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge |
| title_full_unstemmed | Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge |
| title_short | Chemical Abundances in the Nuclear Star Cluster of the Milky Way: Alpha-element Trends and Their Similarities with the Inner Bulge |
| title_sort | chemical abundances in the nuclear star cluster of the milky way alpha element trends and their similarities with the inner bulge |
| topic | Galactic center Chemical abundances Galactic archaeology M giant stars Near infrared astronomy High resolution spectroscopy |
| url | https://doi.org/10.3847/1538-4357/ad9b2b |
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