Subproject A5: Observational Galactic Chemodynamics

The RAdial Velocity Experiment (RAVE), which concluded its decade-long observations during the first funding period after having obtained around half a million stellar spectra, was our primary data source. Numerous papers on RAVE results were published during the last four years, assisted by the abundance analyses done in subproject A5. Our findings include the detection of kinematic asymmetries in the local disk and improved determinations of the local standard of rest. Most of the kinematic star groups found in RAVE were shown to be dynamical effects of the Galactic bar and spiral arms; only a few appear to be genuine remnants of accretion events. Chemical gradients and orbit estimates suggest that radial migration is unlikely to have been the main cause for the formation of the thick disk. Gas-rich mergers and subsequent in-situ star formation appear to be a more likely culprit. A general-purpose automated spectroscopic abundance analysis code (“SPACE”) was developed, which we plan to release in the second funding period. Considerable effort was spent also on the abundance analysis of spectra from the Gaia-ESO Survey, in which the members of subproject A5 participate. The results will be released to the public by the Gaia-ESO collaboration.

In the second funding period, we want to explore the chemodynamical evolution of the Galactic disk combining data mainly from RAVE, the Gaia-ESO Survey, and Gaia. Using 6-D phase-space information, abundances, and ages we can study vertical and radial chemical gradients in the disk as a function of spatial position, kinematics, and approximate age. We will study age-metallicity and age-metallicity-velocity dispersion relations throughout the sampled disk volumes and use the results in collaboration with A6 to constrain disk formation scenarios. Methodologically, we will develop a code that makes it possible to combine spectroscopic data, multi-color photometry, and parallaxes from different surveys and to exploit all of them in a homogeneous way. This will be accompanied by the development of 1-D and 3-D NLTE codes for abundance determinations.