We present abundances for seven stars in the ( extremely ) low-metallicity tail of the Sculptor dwarf spheroidal galaxy , from spectra taken with X-shooter on the ESO VLT .
Targets were selected from the Ca II triplet ( CaT ) survey of the Dwarf Abundances and Radial Velocities Team ( DART ) using the latest calibration .
Of the seven extremely metal-poor candidates , five stars are confirmed to be extremely metal-poor ( i.e. , [ Fe/H ] < -3 dex ) , with [ Fe/H ] =-3.47 \pm 0.07 for our most metal-poor star .
All have [ Fe/H ] \leq - 2.5 dex from the measurement of individual Fe lines .
These values are in agreement with the CaT predictions to within error bars .
None of the seven stars is found to be carbon-rich .
We estimate a 2–13 % possibility of this being a pure chance effect , which could indicate a lower fraction of carbon-rich extremely metal-poor stars in Sculptor compared to the Milky Way halo .
The [ \alpha /Fe ] ratios show a range from +0.5 to –0.5 , a larger variation than seen in Galactic samples although typically consistent within 1–2 \sigma .
One star seems mildly iron-enhanced .
Our program stars show no deviations from the Galactic abundance trends in chromium and the heavy elements barium and strontium .
Sodium abundances are , however , below the Galactic values for several stars .
Overall , we conclude that the CaT lines are a successful metallicity indicator down to the extremely metal-poor regime and that the extremely metal-poor stars in the Sculptor dwarf galaxy are chemically more similar to their Milky Way halo equivalents than the more metal-rich population of stars .