Spectroscopy of giants of the Sagittarius dwarf galaxy

In this paper we present the first results of the analysis of intermediate resolution (Delta lambda similar to 3.5 Angstrom) spectra of giants of the Sagittarius dwarf galaxy acquired using the ESO NTT telescope. From the deep CCD photometry of Marconi et al. (1998a) we have selected a sample of giants representative of the metallicity spread suggested by the comparison of the colour-magnitude diagram of Sagittarius with those of galactic globular clusters. The spectra have been used to measure radial velocities, to confirm the membership to Sagittarius, and to provide a metallicity estimate by using spectral synthesis techniques. The analyzed stars show a spread in metallicities in the range -1.0 less than or equal to [Fe/H] less than or equal to +0.7, some 0.5 dex more metal-rich than the photometric estimates.