The most metal-poor Galactic globular cluster: the first spectroscopic observations of ESO280-SC06

2018/04/02 by Jeffrey D. Simpson
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Cluster (spacecraft) #Galactic halo #Galaxy #Globular cluster #Halo #Physics #Star cluster #Stars #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR

paper · pdf · doi:10.1093/mnras/sty847

12 pages, 12 figures. Accepted for publication in MNRAS

openalex publication_date 2018/04/02 · arxiv created 2018/04/08 · arxiv updated 2018/04/10 · openalex created_date 2018/04/13 · openalex updated_date 2026/08/06

Abstract

We present the first spectroscopic observations of the very metal-poor Milky Way globular cluster ESO280-SC06. Using spectra acquired with the 2dF/AAOmega spectrograph on the Anglo-Australian Telescope, we have identified 13 members of the cluster, and estimate from their infrared calcium triplet lines that the cluster has a metallicity of |[\textrmFe/\textrmH]=-2.48^+0.06 _-0.11|⁠. This would make it the most metal-poor globular cluster known in the Milky Way. This result was verified with comparisons to three other metal-poor globular clusters that had been observed and analysed in the same manner. We also present new photometry of the cluster from EFOSC2 and SkyMapper and confirm that the cluster is located 22.9 ± 2.1 kpc from the Sun and 15.2 ± 2.1 kpc from the Galactic Centre, and has a radial velocity of |92.5^+2.4 _-1.6| km s−1. These new data finds the cluster to have a radius about half that previously estimated, and we find that the cluster has a dynamical mass of the cluster of (12 ± 2) × 103 M⊙. Unfortunately, we lack reliable proper motions to fully characterize its orbit about the Galaxy. Intriguingly, the photometry suggests that the cluster lacks a well-populated horizontal branch, something that has not been observed in a cluster so ancient or metal poor.

Citations

• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A*
• New cluster members and halo stars of the Galactic globular cluster NGC 1851
• The Sloan Digital Sky Survey Photometric Camera
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters without PreviousHubble Space TelescopePhotometry
• The near-infrared Ca ii triplet as a metallicity indicator – II. Extension to extremely metal-poor metallicity regimes★
• MEASURING REDDENING WITH SLOAN DIGITAL SKY SURVEY STELLAR SPECTRA AND RECALIBRATING SFD
• The Dartmouth Stellar Evolution Database
• A Catalog of Parameters for Globular Clusters in the Milky Way
• Metallicity and Alpha‐Element Abundance Measurement in Red Giant Stars from Medium‐Resolution Spectra
• A CH star in the globular cluster NGC 6426
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• The Two Micron All Sky Survey (2MASS)
• DAOPHOT - A computer program for crowded-field stellar photometry
• Globular clusters as the relics of regular star formation in ‘normal’ high-redshift galaxies
• KIM 3: AN ULTRA-FAINT STAR CLUSTER IN THE CONSTELLATION OF CENTAURUS
• The Galaxy in Context: Structural, Kinematic, and Integrated Properties
• The Pan-STARRS1 Surveys
• Gaia 1 and 2. A pair of new Galactic star clusters
• Multiple Stellar Populations in Globular Clusters
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• HEAVY-ELEMENT DISPERSION IN THE METAL-POOR GLOBULAR CLUSTER M92
• Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters