We demonstrate that low-resolution CaII triplet (CaT) spectroscopic estimates of the overall metallicity ([Fe/H]) of individual red giant branch (RGB) stars in two nearby dwarf spheroidal galaxies (dSphs) agree to +/-0.1-0.2dex with detailed high-resolution spectroscopic determinations for the same stars over the range -2.5<[Fe/H]<-0.5. For this study, we used a sample of 129 stars observed in low- and high-resolution modes with VLT/FLAMES in the Sculptor and Fornax dSphs. We also present the data-reduction steps we used in our low-resolution analysis and show that the typical accuracy of our velocity and CaT [Fe/H] measurement is ~2km/s and 0.1dex, respectively. We conclude that CaT[Fe/H] relations calibrated on globular clusters can be applied with confidence to RGB stars in composite stellar populations over the range -2.5<[Fe/H]<-0.5.

Cone search capability for table J/MNRAS/383/183/table3 (Sample of the relevant data for the stars in the globular clusters NGC 104, NGC 3201, NGC 4590 and NGC 5904 observed with VLT/FLAMES at low resolution, and that we used in the analysis of the CaT-[Fe/H] calibration.)

Cone search capability for table J/MNRAS/383/183/table4 (Sample of the relevant data for the stars observed with VLT/FLAMES at both low- and high-resolution and in the Sculptor and Fornax dSphs, and used in the analysis of the CaT-[Fe/H] calibration.)