A homogeneous chemical analysis of the inner Galactic disk from the first data release of Gaia-ESO

One of the open questions of modern astrophysics is how galaxies, and in particular disk galaxies as the Milky Way, form and evolve within the currently accepted cosmological framework. One way to tackle this question is to perform a detailed examination of our own Galaxy by spatially mapping the kinematic and chemical properites of stars of different ages within the Galaxy, i.e. the fossil records of the past evolutionary processes.

Gaia-ESO is a public spectroscopic survey designed with this goal in mind. The survey will provide high-resolution spectra, obtained with the instruments GIRAFFE and UVES at the VLT, of more than hundred thousand stars in the Milky Way, systematically covering all its major components: the bulge, the thick and thin disks and the halo. These spectra will allow to determine the abundances of individual chemical elements in each star, in addition to yielding precise radial velocities. This information, coupled to the accurate astrometry supplied by the Gaia mission, will provide an homogeneous overview of the spatial distribution of stellar kinematics and chemical abundances from which we can infer the formation history and the evolution of the different components of our Galaxy.

In particular, open star clusters are useful tracers of the formation and evolution processes of our Galaxy, as they are located in the Galactic disk at different distances from the center and span a wide range of ages. By analysing the stellar spectra of three open clusters from the first data release of Gaia-ESO, Laura Magrini (researcher at the Observatory of Arcetri) and collaborators were able to determine the chemical composition of these systems and compare them with field stars, analysed in a homogeneous way. Comparing the abundance pattern of the open clusters with stars in the field allows to put constraints on models of chemical evolution and on the birthplace of open clusters. These first results highlight the potential of the Gaia-ESO survey to explore areas of the Milky Way still poorly studied, such as the inner disk, and to give new constraints on Galactic chemical evolution models.
The results of this study are published in the article "The Gaia-ESO Survey: Abundance ratios in the inner-disk open clusters Trumpler 20, NGC 4815, NGC 6705", by L. Magrini et al, Astronomy & Astrophysics (in press).

Map of observed targets of the first data release of the Gaia-ESO Survey. The Principal Investigators of the Gaia-ESO project are Sofia Randich (INAF-Observatory of Arcetri) and Gerry Gilmore (Institute of Astronomy, Cambridge). The consortium involves more than 250 active partecipants, with a significant contribution from the Astrophysical Observatory of Arcetri.

Edited by Anna Gallazzi