A MUSE study of the inner bulge globular cluster Terzan 9: a fossil record in the Galaxy

Abstract

Context. Moderately metal-poor inner bulge globular clusters are relics of a generation of long-lived stars that formed in the early Galaxy. Terzan 9, projected at 4d 12 from the Galactic center, is among the most central globular clusters in the Milky Way, showing an orbit which remains confined to the inner 1 kpc. Aims. Our aim is the derivation of the cluster's metallicity, together with an accurate measurement of the mean radial velocity. In the literature, metallicities in the range between have been estimated for Terzan 9 based on color-magnitude diagrams and CaII triplet (CaT) lines. Aims. Our aim is the derivation of the cluster's metallicity, together with an accurate measurement of the mean radial velocity. In the literature, metallicities in the range between -2.0 and -1.0 have been estimated for Terzan 9 based on color-magnitude diagrams and CaII triplet (CaT) lines. Methods. Given its compactness, Terzan 9 was observed using the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope. The extraction of spectra from several hundreds of individual stars allowed us to derive their radial velocities, metallicities, and [Mg/Fe]. The spectra obtained with MUSE were analysed through full spectrum fitting using the ETOILE code. Results. We obtained a mean metallicity of [Fe/H] -1.10 0.15, a heliocentric radial velocity of vhr = 58.1 1.1 km/s , and a magnesium-to-iron [Mg/Fe] = 0.27 0.03. The metallicity-derived character of Terzan 9 sets it among the family of the moderately metal-poor Blue Horizontal Branch clusters HP 1, NGC 6558, and NGC 6522.

References in corpus (11)

• Oxygen, Sodium, Magnesium and Aluminium as tracers of the Galactic Bulge Formation
• A stellar census in globular clusters with MUSE: The contribution of rotation to cluster dynamics studied with 200 000 stars
• Near-IR properties of 24 Globular Clusters in the Galactic Bulge
• The GIRAFFE Inner Bulge Survey (GIBS) III. Metallicity distributions and kinematics of 26 Galactic bulge fields
• The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge
• The chemical evolution of Manganese in different stellar systems
• High-resolution abundance analysis of red giants in the globular cluster NGC 6522
• Proper motions and kinematics of selected bulge globular clusters
• A Deep View of a Fossil Relic in the Galactic Bulge: The Globular Cluster HP1
• Ages of the Bulge globular clusters NGC 6522 and NGC 6626 (M28) from HST Proper-motion-cleaned Color-Magnitude Diagrams
• FORS2/VLT survey of Milky Way globular clusters I. Description of the method for derivation of metal abundances in the optical and application to NGC 6528, NGC 6553, M 71, NGC 6558, NGC 6426 and Terzan 8

Cited by in corpus (2)

• CAPOS: The bulge Cluster APOgee Survey I. Overview and initial ASPCAP results
• UVES analysis of red giants in the bulge globular cluster NGC 6522