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

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 towards the Galactic Bulge. Using \textit{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), $\alpha$-(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 \textit{Gaia}-Enceladus-Sausage structures.

arXiv commentAccepted for publication in The Astrophysical Journal Letters. 9 pages, 4 figures, 1 table

References in corpus (42)

• Planck 2015 results. XIII. Cosmological parameters
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Gaia Data Release 2: The astrometric solution
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Dartmouth Stellar Evolution Database
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• ASPCAP: The Apogee Stellar Parameter and Chemical Abundances Pipeline
• A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters
• Mean proper motions, space orbits and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data
• Origin of the system of globular clusters in the Milky Way
• The Data Reduction Pipeline for the Apache Point Observatory Galactic Evolution Experiment
• Target Selection for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• Target Selection for the SDSS-IV APOGEE-2 Survey
• APOGEE Data Releases 13 and 14: Data and Analysis
• The Sausage Globular Clusters
• Homogeneous Analysis of Globular Clusters from the APOGEE Survey with the BACCHUS Code. II. The Southern Clusters and Overview
• VIRAC: The VVV Infrared Astrometric Catalogue
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• The pattern speed of the Milky Way bar from transverse velocities
• Reddening and metallicity maps of the Milky Way Bulge from VVV and 2MASS. I.The method and minor axis maps
• APOGEE Chemical Abundances of Globular Cluster Giants in the Inner Galaxy
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge
• The tidal remnant of an unusually metal-poor globular cluster
• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• Globular clusters in the inner Galaxy classified from dynamical orbital criteria
• Analysis of the physical nature of 22 New VVV Survey Globular Cluster candidates in the Milky Way Bulge
• The minimum metallicity of globular clusters and its physical origin -- implications for the galaxy mass-metallicity relation and observations of proto-globular clusters at high redshift
• Aluminum Enhanced Metal-Poor Stars buried in the Inner Galaxy
• Discovery of a new stellar sub-population residing in the (inner) stellar halo of the Milky Way
• H-band discovery of additional Second-Generation stars in the Galactic Bulge Globular Cluster NGC 6522 as observed by APOGEE and Gaia
• Self-consistent analysis of stellar clusters: An application to HST data of the halo globular cluster NGC 6752
• Dynamical Orbital classification of selected N-rich stars with \textit{Gaia} DR2 astrometry
• The enigmatic globular cluster UKS~1 obscured by the bulge: \textit{H}-band discovery of nitrogen-enhanced stars
• VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk
• Discovery of a nitrogen-enhanced mildly metal-poor binary system: Possible evidence for pollution from an extinct AGB Star
• Discovery of a large population of Nitrogen-Enhanced stars in the Magellanic Clouds
• Jurassic: A Chemically Anomalous Structure in the Galactic Halo
• The most metal-poor Galactic globular cluster: the first spectroscopic observations of ESO280-SC06

Cited by in corpus (27)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• The Chemo-Dynamical Groups of Galactic Globular Clusters
• The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy
• Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO) I. An updated census of APOGEE N-rich giants across the Milky Way
• APOGEE spectroscopic evidence for chemical anomalies in dwarf galaxies: The case of M~54 and Sagittarius
• Star Cluster Formation and Survival in the First Galaxies
• A census of new globular clusters in the Galactic bulge
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• Milky Way globular clusters on cosmological timescales. I. Evolution of the orbital parameters in time-varying potentials
• CAPOS: the bulge Cluster APOgee Survey II. The Intriguing "Sequoia" Globular Cluster FSR 1758
• Classifying globular clusters and applying them to estimate the mass of the Milky Way
• Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates
• CAPOS: The bulge Cluster APOgee Survey III. Spectroscopic Tomography of Tonantzintla 2
• Orbits of globular clusters computed with dynamical friction in the Galactic anisotropic velocity dispersion field
• APOGEE-2S Discovery of Light- and Heavy-Element Abundance Correlations in the Bulge Globular Cluster NGC 6380
• APOGEE-2S view of the globular cluster Patchick 125 (Gran 3). New metallicity and elemental abundances from high-resolution spectroscopy
• Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO) II. t-SNE Portrait of Local Fossil Relics and Structures
• Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge
• Ca Triplet Metallicities and Velocities for twelve Globular Clusters towards the Galactic Bulge
• APOGEE-2 Discovery of a Large Population of Relatively High-Metallicity Globular Cluster Debris
• CAPOS: The bulge Cluster APOgee Survey V. Elemental abundances of the bulge globular cluster HP 1
• The VISCACHA survey -- V. Rejuvenating three faint SMC clusters
• CAPOS: The bulge Cluster APOgee Survey VIII. Final ASPCAP results for all clusters
• Variable stars in the VVV globular clusters. II. NGC6441, NGC6569, NGC6626 (M28), NGC6656 (M22), 2MASS-GC02, and Terzan10
• Infrared photometry and CaT spectroscopy of the most metal-poor in-situ globular cluster VVV-CL001
• Photo-chemo-dynamical analysis and the origin of the bulge globular cluster Palomar 6
• Spectroscopic analysis of VVV CL001 cluster with MUSE