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

Spina, L.; Randich, S.; Palla, F.; Biazzo, K.; Sacco, G. G.; Alfaro, E. J.; Franciosini, E.; Magrini, L.; Morbidelli, L.; Frasca, A.; Adibekyan, V.; Delgado-Mena, E.; Sousa, S. G.; Gonzalez Hernandez, J. I.; Montes, D.; Tabernero, H.; Tautvaisiene, G.; Bonito, R.; Lanzafame, A. C.; Gilmore, G.; Jeffries, R. D.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Korn, A. J.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Bergemann, M.; Costado, M. T.; Damiani, F.; Hill, V.; Hourihane, A.; Jofre, P.; de Laverny, P.; Lardo, C.; Masseron, T.; Prisinzano, L.; Worley, C. C.
Astronomy & Astrophysics, Volume 568, id.A2, 12 pp. (2014).


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. 
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. 
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. 
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