Its name is SoS – the Survey of Surveys - and it represents the synthesis of spectroscopic measurements available in the large spectroscopic surveys for all the Milky Way stars. The project is led by Italian scientists, with INAF-Florence leading the scientific analysis of data, and SSDC-ASI leading the cross-match and database management.
The research group led by Maria Tsantaki, postdoctoral researcher in INAF-Florence, used the catalogue produced by the ESA Gaia mission as reference. The Gaia catalogue contains almost two billion stars, many of them also present in the surveys included in the SoS catalogue. "The data we release will allow to better characterize the stars that are hosting planets in order to better determine their properties, such as mass, radius and therefore density, and hence to distinguish the terrestrial planets from the gaseous ones," says Tsantaki.
"We are in the large astronomical surveys era. Large observational campaigns - in particular spectroscopic ones - together with asteroseismology and Gaia are changing dramatically our knowledge of the Milky Way and stellar astrophysics", adds Elena Pancino, INAF scientist in Florence.
Astronomical surveys generally include several types of stars and are built from different instruments and telescopes located on both Earth hemispheres. In addition, the measurements obtained are analysed using different methods, and finally presented in several catalogues having their own format and content. Until now, there was no single and uniform reference catalogue for spectroscopic measurements. The SoS, the largest catalogue of radial velocity to date containing data for more than eleven million stars, was created through the recalibration of all large surveys (APOGEE, RAVE, GALAH, GES, LAMOST) on a single reference scale.
"The software developed at SSDC for the Gaia official cross-match, was the starting point for the exploitation of the extensive knowledge acquired by the scientific team in performing calibrations", says Paola Marrese, INAF scientist at SSDC. "The content of the Survey of Surveys will be hosted and made publicly available through GaiaPortal, the Italian gateway to access the Gaia data developed by SSDC as Gaia Partner Data centre", adds Silvia Marinoni, INAF scientist at SSDC.
The first stellar parameter published in the SoS is the radial velocity, with an accuracy of about 300 m/s and a precision of about 0.5-2 km/s (a very good quality for such a large and composite catalogue). In the future, the SoS catalogue will include further stellar parameters and detailed chemical information. These data will be very useful for the scientific community to study the formation and evolution of the Milky Way, also through the knowledge of its star clusters, and to better characterize the stars hosting planets.
Currently the research group is working on stellar parameters such as surface temperature and gravity, metallicity, and various chemical species abundancies. This second phase of the work is expected to last a couple of years. Once completed and released, the catalogue will enter the routine maintenance phase, to keep the SoS always updated. A collaboration for the scientific exploitation of the catalogue is also ongoing involving the galactic archaeology research group at the Instituto de Astrofísica de Canarias (IAC) in Tenerife, Canary Islands.
For further information:
The paper "Survey of Surveys I: The largest compilation of radial velocities for the Galaxy", by M. Tsantaki, E. Pancino, P. Marrese, S. Marinoni, M. Rainer, N. Sanna, A. Turchi, S Randich, C. Gallart, G. Battaglia and T. Masseron was published online in Astronomy & Astrophysics journal.
The SoS catalogue is available through GaiaPortal at http://gaiaportal.ssdc.asi.it/