A MUSE study of the inner bulge globular cluster Terzan 9: A fossil record in the Galaxy
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2019-12
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Facultad/escuela
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en
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Licencia CC
Licencia CC
Resumen
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 4°.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-2.0 < [Fe/H] < -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-1, 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. © ESO 2019.
Notas
IDEXACIÓN:SCOPUS
Palabras clave
Galaxy: bulge; Globular clusters: individual: Terzan 9; Stars: Abundances
Citación
Astronomy and AstrophysicsOpen AccessVolume 6321 December 2019 Article number A103