Run of the iron abundances as a function of the effective temperature for the seven UVES stars (blue circles) and stars with GIRAFFE spectra (red circles). Abundances from singly ionised Fe lines are shown in the lower panel for UVES stars only. Internal error bars are also displayed (for the UVES sample on the left corner, for the GIRAFFE sample in the right corner). The dotted line is the average abundance derived from the UVES spectra.