Gaia @ INAF-OAPd
Gaia is a ESA Cornerstone Mission which is expected to measure distances, parallaxes, proper motions, spectro-photometry of 1 billion stars in our Galaxy down to V=20 mag with the aim of
After Gaia 50 million stars brighter than V=15 will have:
- their
space velocity vectors known to better than 3 km/s - their
distance better than 10% - their
temperature, gravity and metallicity to better than 2%, 0.18 dex and 0.15 dex, respectively.
The direct determination of the 6D phase space distribution as well as of the chemical abundance of large and complete samples of different stellar populations will make it possible to interpret coherently the evolutionary scenarios of the whole Milky Way.
During the past years this Institute was directly involved in the working groups in charge of the definition of the instrument characteristics needed to meet the goal ( Munari 1999, Bertelli, Vallenari, Pasetto 2003, Wilkinson, Vallenari et al 2005, Jordi et al. 2006 Jordi et al 2006 and the Gaia internal reports) . One of us (Dr. U. Munari) was the leader of the Spectroscopic working group, while Dr. A. Vallenari is responsible for the Training Data work Package in the Coordination Unit 8 of the Data Process and Analysis Consortium.
- collaborating with INAF-OABO to provide the
absolute calibration of the Gaia photometric system . This will be achieved by using a set of Spectro-Photometric Standard Stars (SPSS) with well known and accurately calibrated SEDs over the entire wavelength range of the Gaia spectro-photometric system. This task requires studies to select the most suitable SPSS, ground-based observational campaigns at ESO and Italian telescopes monitoring for variability, and simulations of the expected performances of the Gaia instruments. - developing new models and methods to derive the astrophysical parameters of stellar objects and non-stellar objects such as galaxies and QSOs using a detailed analysis of the photometric and spectroscopic data of Gaia. This includes
calculating and maintaining libraries of synthetic and observational stellar spectra for 'normal' stars at high resolution, to be used as training data for the classification algorithms used to derive the stellar parameters. Libraries of synthetic galaxies and QSOs and galaxies are and will be produced and integrated with observational data (Tsalmantza et al 2006, 2007).Libraries of stellar tracks and isochrones at varying stellar parameters are already or are expected to be produced in the coming future (Nasi et al 2007).
Synthetic spectral libraries
Recently, high resolution synthetic stellar libraries calculated for the Gaia mission are produced. They cover two spectral ranges: 300-1100 nm at 0.1 nm resolution, and 840-890 nm at 0.001 nm resolution. These libraries span a large range in atmospheric parameters, from super-metal-rich to very metal-poor (-5.0<[Fe/H]<+1.0), from cool to hot (Teff=3000-50000 K) stars, including peculiar abundance variations. The spectral resolution, spectral type coverage and number of models represent a substantial improvement over previous libraries used in population synthesis models and in atmospheric analysis. This work is done in collaboration with Thevenin (OCA, NIce), Korn , Gustaffson (Uppsala), and all the Gaia Spectral libraries Provider Group.
One of us (A. Vallenari) is top level manager of the Data Training Working Package being responsible of the preparation of training data for the DPAC simulations.