We present metallicities and ages for 52 red giants in the remote Galactic dwarf spheroidal ( dSph ) galaxy Leo II .
These stars cover the entire surface area of Leo II and are radial velocity members .
We obtained medium-resolution multi-fiber spectroscopy with the FLAMES multi-object spectrograph as part of a Large Programme with the Very Large Telescope at the European Southern Observatory , Chile .
The metallicities were determined based on the well-established near-infrared Ca ii triplet technique .
This allowed us to achieve a mean random error of 0.16 dex on the metallicities , while other systematic effects , such as unknown variations in the dSph ’ s [ Ca/Fe ] -ratio , may introduce a further source of uncertainty of the order of 0.1 dex .
The resulting metallicity distribution is asymmetric and peaks at [ Fe/H ] = -1.74 dex on the Carretta & Gratton scale .
The full range in metallicities extends from -2.4 to -1.08 dex .
As in other dSph galaxies , no extremely metal-poor red giants were found .
We compare Leo II ’ s observed metallicity distribution with model predictions for several other Galactic dSphs from the literature .
Leo II clearly exhibits a lack of more metal poor stars , in analogy to the classical G-dwarf problem , which may indicate a comparable “ K-giant problem ” .
Moreover , its evolution appears to have been affected by galactic winds .
We use our inferred metallicities as an input parameter for isochrone fits to Sloan Digital Sky Survey photometry of our target stars and derive approximate ages .
The resulting age-metallicity distribution covers the full age range from 2 to about 15 Gyr on our adopted isochrone scale .
During the first \sim 7 Gyr relative to the oldest stars the metallicity of Leo II appears to have remained almost constant , centering on the mean metallicity of this galaxy .
The almost constant metallicity at higher ages and a slight drop by about 0.3 dex thereafter may be indicative of rejuvenation by low metallicity gas .
Overall , the age-metallicity relation appears to support the formation of Leo II from pre-enriched gas .
Evidence for enrichment is seen during the recent 2 to 4 Gyr .
Our findings support earlier derived photometric findings of Leo II as a galaxy with a prominent old population and dominant intermediate-age populations .
We do not see a significant indication of a radial metallicity gradient nor age gradient in our current data .