Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 908, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/2041-8213/abdf47
Keywords
Globular star clusters; Chemical abundances; Red giant branch
Categories
Funding
- BASAL Center for Astrophysics and Associated Technologies (CATA) [AFB 170002]
- FAPESP [2018/22044-3]
- Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE) - US National Science Foundation [PHY 14-30152]
- Chilean Centro de Excelencia en Astrofisica y Tecnologias Afines (CATA) BASAL grant [AFB170002]
- Direccion de Investigacion y Desarrollo de la Universidad de La Serena through the Programa de Incentivo a la Investigacion de Academicos (PIA-DIDULS)
- Fondecyt [1170518, 3180210, 1170121]
- FAPESP
- CNPq
- CAPES [001]
- DGAPA-PAPIIT [IG100319]
- Agency for Research and Development (ANID)/CONICYT-PFCHA/DOCTORADO NACIONAL/2017 [21171231]
- Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) through the FONDECYT 17 project [1170476]
- Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) through the QUIMAL project [130001]
- Alfred P. Sloan Foundation
- U.S. Department of Energy Office of Science
- Center for High-Performance Computing at the University of Utah
- Brazilian Participation Group
- Carnegie Institution for Science
- Carnegie Mellon University
- Chilean Participation Group
- French Participation Group
- Harvard-Smithsonian Center for Astrophysics
- Instituto de Astrofisica de Canarias
- Johns Hopkins University
- Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo
- Lawrence Berkeley National Laboratory
- Leibniz Institut fur Astrophysik Potsdam (AIP)
- Max-Planck-Institut fur Astronomie (MPIA Heidelberg)
- Max-Planck-Institut fur Astrophysik (MPA Garching)
- Max-Planck-Institut fur Extraterrestrische Physik (MPE)
- National Astronomical Observatory of China
- New Mexico State University
- New York University
- University of Notre Dame
- Observatorio Nacional/MCTI
- Ohio State University
- Pennsylvania State University
- Shanghai Astronomical Observatory
- United Kingdom Participation Group
- Universidad Nacional Autonoma de Mexico
- University of Arizona
- University of Colorado Boulder
- University of Oxford
- University of Portsmouth
- University of Utah
- University of Virginia
- University of Washington
- University of Wisconsin
- Vanderbilt University
- Yale University
- Graduate School of the Universidad de Antofagasta
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The study provides the first high-resolution abundance analysis of the globular cluster VVV CL001, suggesting that it may be one of the most metal-deficient clusters in the Galaxy. By applying statistical isochrone fitting, the estimated age of VVV CL001 is around 11.9 Gyr with a distance of approximately 8.22 kpc, indicating that it is an ancient globular cluster in the inner Galaxy. The chemical composition and dynamics support the hypothesis that VVV CL001 could be an ancient fossil relic left behind by a massive merger event during the early evolution of the Galaxy.
We present the first high-resolution abundance analysis of the globular cluster VVV CL001, which resides in a region dominated by high interstellar reddening toward the Galactic bulge. Using H-band spectra acquired by the Apache Point Observatory Galactic Evolution Experiment, we identified two potential members of the cluster, and estimated from their Fe I lines that the cluster has an average metallicity of [Fe/H] = -2.45 with an uncertainty due to systematics of 0.24 dex. We find that the light-(N), alpha-(O, Mg, Si), and Odd-Z (Al) elemental abundances of the stars in VVV CL001 follo w the same trend as other Galactic metal-poor globular clusters. This makes VVV CL001 possibly the most metalpoor globular cluster identified so far within the Sun's galactocentric distance and likely one of the most metaldeficient clusters in the Galaxy after ESO280-SC06. Applying statistical isochrone fitting, we derive self-consistent age, distance, and reddening values, yielding an estimated age of 11.9(-4.05)(+3.12) Gyr at a distance of 8.22(-1.93)(+1.84) kpc, revealing that VVV CL001 is also an old GC in the inner Galaxy. The Galactic orbit of VVV CL001 indicates that this cluster lies on a halo-like orbit that appears to be highly eccentric. Both chemistry and dynamics support the hypothesis that VVV CL001 could be an ancient fossil relic left behind by a massive merger event during the early evolution of the Galaxy, likely associated with either the Sequoia or the Gaia-Enceladus-Sausage structures.
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