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 .
( 50 ) 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 % 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 .