VVV CL001: Likely the Most Metal-poor Surviving Globular Cluster in the Inner Galaxy

José G. Fernández-Trincado, Dante Minniti, Stefano O. Souza, Timothy C. Beers, Doug Geisler, Christian Moni Bidin, Sandro Villanova, Steven R. Majewski, Beatriz Barbuy, Angeles Pérez-Villegas, Lady Henao, Mariá Romero-Colmenares, Alexandre Roman-Lopes, Richard R. Lane

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


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), -(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 metal-poor globular cluster identified so far within the Sun's galactocentric distance and likely one of the most metal-deficient 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 Gyr at a distance of 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.

Original languageEnglish
Article numberL42
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 20 Feb 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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