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

Longeard, Nicolas; Martin, Nicolas; Ibata, Rodrigo A.; Starkenburg, Else; Jablonka, Pascale; Aguado, David S.; Carlberg, Raymond G.; Côté, Patrick; González Hernández, Jonay I.; Lucchesi, Romain; Malhan, Khyati; Navarro, Julio F.; Sánchez-Janssen, Rubén; Thomas, Guillaume F.; Venn, Kim; McConnachie, Alan W.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society

Advertised on:
We present a new spectroscopic study of the faint Milky Way satellite Sagittarius II. Using multiobject spectroscopy from the Fibre Large Array Multi-Element Spectrograph, we supplement the data set of Longeard et al. 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 $\sigma _\mathrm{v}^\mathrm{SgrII} = 1.7 \pm 0.5$ 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] $_\mathrm{spectro}^\mathrm{SgrII} = -2.23 \pm 0.07$ ) 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.
Related projects
spectrum of mercury lamp
Chemical Abundances in Stars

Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to

Allende Prieto