We have obtained metallicities of \sim 360 red giant stars distributed in 15 Small Magellanic Cloud ( SMC ) fields from near-infrared spectra covering the Ca ii triplet lines using the VLT + FORS2 .
The errors of the derived [ Fe/H ] values range from 0.09 to 0.35 dex per star , with a mean of 0.17 dex .
The metallicity distribution of the whole sample shows a mean value of [ Fe/H ] = -1.00 \pm 0.02 , with a dispersion of 0.32 \pm 0.01 , in agreement with global mean [ Fe/H ] values found in previous studies .
We find no evidence of a metallicity gradient in the SMC .
In fact , on analysing the metallicity distribution of each field , we derived mean values of [ Fe/H ] = -0.99 \pm 0.08 and [ Fe/H ] = -1.02 \pm 0.07 for fields located closer and farther than 4 ^ { \circ } from the center of the galaxy , respectively .
In addition , there is a clear tendency for the field stars to be more metal-poor than the corresponding cluster they surround , independent of their positions in the galaxy and of the clusters ’ age .
We argue that this most likely stems from the field stars being somewhat older and therefore somewhat more metal-poor than most of our clusters .