MPIA contributions to CU9
As part of the products from DPAC, Apsis and in particular GSP-Phot will infer the stellar properties of each individual star from their BP/RP spectrum, while accounting for parallaxes (i.e. distance) and interstellar extinction along the line of sight to the stars. Extinction hampers the determination of the intrinsic properties of the stars. Despite the parallax information provided by Gaia, inferring these properties may often not lead to precise estimates, especially for the faint stars.
The main mission goal for CU9 is to provide a comprehensive repository of the rich data products to be generated by Gaia, and a range of access mechanisms and associated helper applications to enable effective access to the Gaia data by the end user science community. It role is in other words to facilitate the interface between Gaia data and science. It is broad and very challenging.
Our role in CU9 is to provide cross-matched catalogs of Gaia sources with external large surveys. ``Hybrid catalogs'' will provide an exquisite value-added catalog of astrophysical parameters for Gaia targets by taking into account the non-Gaia data (e.g. SDSS, WISE, Pan-STARRS, APOGEE, PPMXL, 2MASS, Tycho).
We aim to provide specifically designed catalogs to answer the needs of science applications based on Gaia data and external information (e.g. extinction dominated regions, stellar clusters, rare evolution phases). We will sometimes refine the astrophysical parameters of the Gaia sources with the addition of external information, such as other wavelength measurements, specific models or consideration on of the stellar populations of interests (e.g. coeval populations). By including spectroscopic indicators of metallicity when available, or infrared photometry, we can reduce the degeneracies between extinction and temperature and improve the estimation of metallicity and surface gravity.