Il ruolo della spettroscopia a grande campo per Gaia B. Bucciarelli - INAF/Osservatorio Astronomico di Torino S. Randich - INAF /Osservatorio Astrofisico di Arcetri

2 Gaia: Scientific Organisation  Gaia Science Team (GST):  8 members + ESA Project Scientist (T. Prusti)  Scientific community  organised in Data Processing and Analysis Consortium (DPAC)  ~ 391 scientists from ESA member States  Data distribution policy:  final catalogue ~ 2019–20  intermediate catalogues as appropriate  science alerts data released immediately  no proprietary data rights Strong involvement of Italian community: GST: S. Randich (Arcetri) DPACE: R. Drimmel, Deputy (Torino) DPAC: 63 scientists (as of July 08) CU3 deputy: M. Lattanzi (TO) CU5 Man. Team: C. Cacciari (BO)

Italian Participation in DPAC Through ASI contract INAF Institutes: OABo, OACt, OANa, OAPd, OARm, OATe, OATo (+ OATs) Involvement in all main CUs. Providing over 30 FTEs for more than 60 collaborators (second only to France) Organization: Lead Scientist (“Resp. Scient.”) M.G. Lattanzi Coordination Group: Cacciari, Drimmel, A. Lanzafame, Pulone, Ripepi, Sarasso (project controller), Vallenari

4 GAIA vs. Hipparcos HipparcosGAIA Completeness~ 9G=20 (V=20-22) Magnitude limit12.4~ 1 mag fainter than compl. N. sources ~ quasars01 million galaxies010 million Astrometric accuracy (  ) (**) ~ 1 mas< 7 μas at V≤ μas at V=15 (*) μas at V=20 Photometry2 bandslow-res spectra nm Radial velocitiesnone1-10 km/s to V=16-17 Target selectioninput cataloguereal-time onboard selection (*) ~ 0.5 mas accuracy from ACS/WFC (FoV 202x202 square arcsec) on well exposed images (Anderson & King 2006) (**) Proper motion accuracy 20% better

5 Distances (  ) as a function of V (Mv)  (  )/  Mv V d(pc) < 0.1% ~ < 1% ~ < 10% ≥

6 Gaia products: photometry (V < 20) Integrated:  white-light (G-band, nm) from the Astrometric Field  BP-band & RP-band  BP- RP colour Dispersed:  Blue (BP, nm) & Red (RP, nm) low resolution spectra Main sequence stars from O5 to M6: G=15, A V =0.0 (Straizys et al. 2006) dispersion 4-32 nm/px dispersion 7-15 nm/px

7 Spectrophotometry RMS internal uncertainties at V = 15  Teff 1 – 5 % for a wide range of Teff  log g 0.1 – 0.4 dex, < 0.1 dex for hot stars (SpT ≤ A)  [Fe/H] F) down to -2.0 dex  Av mag for hot stars ► complete characterisation of stellar populations Courtesy Coryn Bailer-Jones, C. Cacciari Stellar astrophysical parameters (APs)  from BP/RP low res SEDs  via pattern recognition  calibration: input physics & synthetic spectra

8 Radial Velocity Measurement Concept (2/2) Radial velocities to 1-10 km/s for all sources down to V < 16–17 ► radial velocitiy, rotation, chemistry ► more detailed APs for V < 14 Field of view RVS spectrograph CCD detectors Figures courtesy David Katz, C. cacciari Integral field spectrograph Multi-epoch scan R=11,500 λ interval: A

9 GAIA science products: census of … Stellar pops in the Galaxy (based on the Besançon Galaxy model - Robin et al. 2003, 2004)  Disk: 9.0 x 10 8  Thick disk: 4.3 x 10 8  Spheroid: 2.1 x 10 7  Bulge: 1.7 x 10 8 Special objects in the Galaxy  Solar System bodies (~ 10 5 )  extra-solar planets (~ 2 x 10 4 )  binaries & rare stellar types (fast evolutionary phases)  WDs (~ 2 x 10 5 ), BDs (~ 5 x 10 4 ) Outside the Galaxy  brightest stars in nearby (LG) galaxies  supernovae and burst sources (~2x10 4 )  galaxies (~ 10 7 )  redshifts  QSOs (~ 10 6 )  gravitational lensing events: < 100 photometric; a few 10 2 astrometric Fundamental Physics   to ~ 5x10 -7 ( present)

Why wide-field multi-object spectroscopy? RV for objects fainter than V=16-17: complement of Gaia core mission: critical! Discussion within GST 2. - More accurate abundance and AP; - Comprehensive characterization of targets in the Kepler and CoRoT fields Requirements 1.R=R(Gaia) ideal, but R=5,000-8,000 ok 2.R > 20,000

CoRoT and Kepler Missions Ultra high-precision photometers observing pre-defined fields in the northern hemisphere Output: light curves for a few thousands objects in the magnitude range V~12-15 (transiting planets, eclipsing binaries, intrisically variable sources, etc). High-quality spectral coverage will complete the dataset for a comprehensive study of these targets