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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2021

The pristine dwarf-galaxy survey – III. Revealing the nature of the Milky Way globular cluster Sagittarius II

Nicolas Longeard
  • Fonction : Auteur
Rodrigo A Ibata
Else Starkenburg
  • Fonction : Auteur
David Aguado
Raymond Carlberg
Patrick Côté
  • Fonction : Auteur
Jonay Hernández
  • Fonction : Auteur
Romain Lucchesi
  • Fonction : Auteur
Khyati Malhan
Julio Navarro
  • Fonction : Auteur
Rubén Sánchez-Janssen
Guillaume Thomas
Kim Venn
Alan Mcconnachie
  • Fonction : Auteur

Résumé

We present a new spectroscopic study of the faint Milky Way satellite Sagittarius II. Using multi-object spectroscopy from the Fibre Large Array Multi Element Spectrograph, we supplement the dataset of Longeard et al. (2020) with 47 newly observed stars, 19 of which are identified as members of the satellite. These additional member stars are used to put tighter constraints on the dynamics and the metallicity properties of the system. We find a low velocity dispersion of σSgrIIv=1.7±0.5 km s-1, in agreement with the dispersion of Milky Way globular clusters of similar luminosity. We confirm the very metal-poor nature of the satellite ([Fe/H] SgrIIspectro=−2.23±0.07 ) and find that the metallicity dispersion of Sgr II is not resolved, reaching only 0.20 at the 95 per cent confidence limit. No star with a metallicity below -2.5 is confidently detected. Therefore, despite the unusually large size of the system (r h=35.5+1.4−1.2 pc), we conclude that Sgr II is an old and metal-poor globular cluster of the Milky Way.
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Dates et versions

hal-03176198 , version 1 (04-05-2023)

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Nicolas Longeard, Nicolas Martin, Rodrigo A Ibata, Else Starkenburg, Pascale Jablonka, et al.. The pristine dwarf-galaxy survey – III. Revealing the nature of the Milky Way globular cluster Sagittarius II. Monthly Notices of the Royal Astronomical Society, 2021, 503 (2), pp.2754-2762. ⟨10.1093/mnras/stab604⟩. ⟨hal-03176198⟩
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