Stellar populations in the Milky Way: bulge, halo, disk and star forming regions; instrumentation for high resolution spectroscopy

Abstract

The main aim of this project is to study the stellar populations and structure of the Milky Way, in order to better understand its formation and evolution. The targets are stars of the Galactic Bulge, Halo and Disk. The bulge is studied in terms of the chemical composition of individual stars, as well as kinematics and ages of field and globular cluster stars. The interplay between the bar and the oldest globular clusters trapped in the bar is studied by deriving their proper motions and distance. The final goal is to know if the metal-poor stars in the bulge are the oldest in the Galaxy, as this would confirm that the bulge formed first. The Galactic halo is studied through the most metal-poor stars, by carrying out abundance analysis. A selection of new targets, in particular carbon-rich metal-poor stars, is also carried out based on large surveys (Sloan Digital Sky Survey and Hamburg/ESO survey). For both the halo and bulge, the abundance pattern of the metal-poor stars ([Fe/H]=-1.0 in the bulge, and [Fe/H] < -2.0 in the halo) give information on the nature of the first supernovae, that produced the chemical enrichment of the gas from which these stars formed. The Galactic disk is studied through a) old super metal-rich stars that seem to have migrated from the inner parts of the Galaxy; b) metal-rich M dwarfs; c) young stars and star forming regions. The group is expert in spectroscopy of cool stars, using low-resolution spectroscopy for selecting targets, and high spectral resolution for abundance analysis and radial velocity derivation. On the theoretical side, we select atomic and molecular data, including computation of hyperfine structure, and molecular constants, and produce line lists that are checked by comparison with spectra of well-known stars such as the Sun and Arcturus. For this, we use model atmospheres to compute synthetic spectra that are compared with the observed ones. We also produce composite spectra of integrated stellar populations, and intend to use integral field spectroscopy. In the study of star clusters, we also use imaging in optical and near-infrared colors, to produce colour-magnitude diagrams, and deduce their ages. For star forming regions, X-ray data from the satellites XMM-Newton and Chandra have been obtained, in order to identify young stars. Instrumentation is an important part of this project, with mainly the development of the CUBES spectrograph for the VLT/ESO, but also the ECHARPE spectrograph for the OPD/LNA/MCTI, and the MOSAIC multi-object spectrograph for the E-ELT. The CUBES spectrograph is at a stage that needs Research & Development on the ultraviolet properties of new CCD detectors, and on new gratings appropriate to the ultraviolet. These studies are useful for any present/future instrument in the ultraviolet. The MOSAIC spectrograph involves Brazilian expertise on optical fibers. (AU)