Abstract
Abstract 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), α-(O, Mg, Si), and Odd-Z (Al) elemental abundances of the stars in VVV CL001 follow 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 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.
Highlights
The inner1 Milky Way (MW) contain a significant population of globular clusters (GCs) with a wide rangeGCs to more than 300 candidates by the inclusion of objects in the inner Galaxy, including those in the bulge (Geisler et al in prep.).In this context, the high-resolution (R > 22, 0000) capabilities of the near-IR multi-fiber spectrographs of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2; Majewski et al 2017) allow measurement of new parameters with high precision for a large number of Galactic GCs in a homogeneous way.Very metal-poor GCs are preferentially associated with the oldest components of galaxies, and are often used as cosmic clocks to track the enrichment history of their host galaxy (Geisler et al 1995)
Using H band spectra acquired by the Apache Point Observatory Galactic Evolution Experiment (APOGEE), we identified two potential members of the cluster, and estimate 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), α-(O, Mg, Si), and Odd-Z (Al) elemental abundances of the stars in Variables in the Via Lactea survey (VVV) CL001 follow the same trend as other Galactic metal-poor globular clusters
Summary
The inner Milky Way (MW) contain a significant population of globular clusters (GCs) with a wide range. Beyond the intrinsic scientific value of identifying such ancient objects, the measurements of their chemical composition can provide insight into the build-up of the chemical elements in the earliest epoch of the Milky Way. To date, the most metal-poor MW GC known is ESO280-SC06 (located ∼15 kpc from the Galactic center), with an estimated metallicity of [Fe/H]= −2.48+−00..0161 (Simpson 2018), and associated to the GaiaEnceladus-Sausage (GES; Massari et al 2019). The most metal-poor MW GC known is ESO280-SC06 (located ∼15 kpc from the Galactic center), with an estimated metallicity of [Fe/H]= −2.48+−00..0161 (Simpson 2018), and associated to the GaiaEnceladus-Sausage (GES; Massari et al 2019) We report another possible extreme case, VVV CL001, which becomes possibly the most metal-poor GC known inside the Sun’s Galactocentric distance, and likely the most metal-poor GC in the Galaxy. In this Letter, we make use of APOGEE-2 spectra to provide the first spectroscopic study of VVV CL001
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
