Thin Disc and Solar Neighbourhood

Figure 1: Elemental abundances for a small incomplete sample of nearby stars, illustrating the need for elemental abundances to characterise the history of stellar populations (Nissen & Schuster, 2010, A&A, 511, L10)

Figure 2: The figure outlines lines of sight probing the dynamics of spiral arms inside the Galactic plane, including the direction of the Galactic center l=0, and spiral arm tangencies including the scutum arm and the tip of the bar at l=26. The cross indicates the location of the Sun, red lines indicate the location of gaseous spiral arms in the Galactic plane, while the dotted and dashed circles indicate the probable position of corotation and Lindblad resonance radii of the spiral and bar, respectively. Credit: A. Siebert & B. Famaey.

We will obtain UVES spectra for an unbiased sample of ~5000 FG stars within ≥ 1 kpc, for the first high-weight detailed determination of the kinematics-multi-element distribution functions (DFs; Figure 1). This covers both thin and thick discs, and all ages and metallicities. Using field stars and clusters, where ages are also known, we will survey the region from about 6 to > 20 kpc Galactocentric radii, we will trace chemical evolution as a function of age and Galactocentric radius across a disc radial scale length. These are key inputs to models for the formation and evolution of the Galaxy disc. Current estimates suffer from poor statistics, inhomogeneous abundance determinations and absence of data at key ages and orbits (Nordstrom et al., A&A, 418, 989). Our survey will fill these gaps and provide a homogeneous abundance dataset from UVES spectroscopy. We will also address current disc structure, that which hosts the star formation. Spiral structure is fundamental to the dynamics of the disc: it dominates the secular rise in the random velocities of stars, and may even cause radial migration of stars and gas (Antoja et al., 2010, hsa5conf, 370). Currently, we are not even clear about the global morphology of our spiral structure, and the information we have on its dynamics largely relates to gas not stars. We will initiate a study of the kinematic distortion in the disc potential due to the bar/spirals by measuring some 1000s of radial velocities down key arm, inter-arm and near-bar lines of sight (Figure 2).