The Gaia-ESO Survey Metallicity of the Chamaeleon I star-forming region

Context. Recent metallicity determinations in young open clusters and star-forming regions suggest that the latter may be characterized by a slightly lower metallicity than the Sun and older clusters in the solar vicinity. However, these results are based on small statistics and inhomogeneous analyses. The Gaia-ESO Survey is observing and homogeneously analyzing large samples of stars in several young clusters and star-forming regions, hence allowing us to further investigate this issue. <BR /> Aims We present a new metallicity determination of the Chamaeleon I star-forming region, based on the products distributed in the first internal release of the Gaia-ESO Survey. <BR /> Methods The 48 candidate members of Chamaeleon I have been observed with the high-resolution, spectrograph UVES. We use the surface gravity, lithium line equivalent width, and position in the Hertzsprung-Russell diagram to confirm the cluster members, and we use the iron abundance to derive the mean metallicity of the region. <BR /> Results Out of the 48 targets, we confirm 15 high probability members. Considering the metallicity measurements for nine of them, we find that the iron abundance of Chamaeleon I is slightly subsolar with a mean value [Fe/H] = -0.08 0.04 dex. This result agrees with the metallicity determination of other nearby star-forming regions and suggests that the chemical pattern of the youngest stars in the solar neighborhood is indeed more metal-poor than the Sun. We argue that this evidence may be related to the chemical distribution of the Gould Belt that contains most of the nearby star-forming regions and young clusters. Based on observations collected at the ESO telescopes under programme 188.B3002, the Gaia-ESO large public spectroscopic survey.Tables 1-3 are available in electronic form at <A href="http //www.aanda.org/10.1051/0004-6361/201424135/olm">http //www.aanda.org</A>