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We have performed accurate iron abundance measurements for 44 red giants(RGs) in the Carina dwarf spheroidal (dSph) galaxy. We used archival,high-resolution spectra (R~38,000) collected with UVES at ESO/VLT either inslit mode (5) or in fiber mode (39, FLAMES/GIRAFFE-UVES). The sample is morethan a factor of four larger than any previous spectroscopic investigation ofstars in dSphs based on high-resolution (R>38,000) spectra. We did not imposethe ionization equilibrium between neutral and singly-ionized iron lines. Theeffective temperatures and the surface gravities were estimated by fittingstellar isochrones in the V, B-V color-magnitude diagram. To measure the ironabundance of individual lines we applied the LTE spectrum synthesis fittingmethod using MARCS model atmospheres of appropriate metallicity. We foundevidence of NLTE effects between neutral and singly-ionized iron abundances.Assuming that the FeII abundances are minimally affected by NLTE effects, wecorrected the FeI stellar abundances using a linear fit between FeI and FeIIstellar abundance determinations.  We found that the Carina metallicity distribution based on the corrected FeIabundances (44 RGs) has a weighted mean metallicity of [Fe/H]=-1.80 and aweighted standard deviation of sigma=0.24 dex. The Carina metallicitydistribution based on the FeII abundances (27 RGs) gives similar estimates([Fe/H]=-1.72, sigma=0.24 dex). The current weighted mean metallicities areslightly more metal poor when compared with similar estimates available in theliterature. Furthermore, if we restrict our analysis to stars with the mostaccurate iron abundances, ~20 FeI and at least three FeII measurements (15stars), we found that the range in iron abundances covered by Carina RGs (~1dex) agrees quite well with similar estimates based on high-resolution spectra.

The Carina Project. V. The impact of NLTE effects on the iron content