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Synthetic Spectral Libraries for Gaia Vallenari INAF, Osservatorio Astronomico di Padova

Synthetic Spectral Libraries for Gaia Vallenari INAF, Osservatorio Astronomico di Padova. On behalf of Gaia Classification Unit OAPD people R.Sordo G.Bertelli E.Nasi U.Munari C.Chiosi R.Tantalo. Collaborators: Edvardsson, Gustafsson, Korn, Heiter (Uppsala Univ)

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Synthetic Spectral Libraries for Gaia Vallenari INAF, Osservatorio Astronomico di Padova

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  1. Synthetic Spectral Libraries for Gaia • Vallenari • INAF, Osservatorio Astronomico di Padova

  2. On behalf of Gaia Classification Unit OAPD people R.Sordo G.Bertelli E.Nasi U.Munari C.Chiosi R.Tantalo • Collaborators: • Edvardsson, Gustafsson, Korn, Heiter (Uppsala Univ) • deLaverny, Recio-Blanco, Thevenin (OCA) • GHOST team: Bouret, Lanz • Kochukov, Shulyak • Fremat, Zorec, Martins • C. Bailer-Jones (MPIA Heidelberg) • M.Kontizas (Athens Univ) • Lanzafame ( Catania Univ.) • and others

  3. GALACTIC SURVEY

  4. Final Catalog and Classification problem • The Catalog will include astrometric APs and basic APs for stars • No input catalog ----- Needs of a classification of the objects • High priority: • 1.Discrete classification of objects • (single stars, QSOs, unresolved binaries, galaxies, solar system objects) • 2. Identification of QSOs(reference frame) • 3. Basic stellar parameters for single stars as input for RVS data processing • Log(g),Teff, [Fe/H], Av • desirable: • 4.Derivation of L,R, age ,m using parallaxes (and stellar models) • 5. Parametrization of special sources (galaxies…) • Classification of 109 objects to G=20 is ill-defined! • –

  5. Classification scheme

  6. Precision estimate – multilinear regression algorithm HOT (12 000 K Teff 40 000 K), MEDIUM (8000 K Teff 12 000 K) and COOL (3000 K Teff 6000 K)

  7. The classification algorithms (except OCA) based on supervised models. These classify sources or estimate their APs source-by-source based on their similarity to a set of predefined templates. Requested: production of synthetic stellar spectra quality control of derived classes and astrophysical parameters via comparison with non-Gaia estimates on pre-selected (stellar)populations ground-based observations for calibration of AP estimation algorithms Classification algorithm development

  8. DATA BASES FOR GAIA synthetic / observationalstellar spectra : (Sordo Munari et al 2005) The Asiago Database on Photometric Systems (ADPS) and spectrahttp://archives.pd.astro.it/2500-10500/ synthetic/observationalgalaxy spectra (PD-Athens-Paris collaboration) (Tzalmatza et al 2006, 2007) Stellar tracks and isochrones at changing He content (Bertelli, Nasi et al 2008) web site: http://stev.oapd.inaf.it/YZVAR Z=0.0001—0.07 Y=0.23—0.40 (0.46 for Z> Zo) (39 sets of tracks) A new data base of synthetic stellar spectra

  9. Synthetic versus Empirical stellar Libraries Refined high resolution stellar spectra are of fundamental importance in the Gaia era, first topredict the response of the instruments andthento interprete the observations In the literature, both empirical & theoretical librariesare used for this purpose. However it is still debated which one is preferable. Empirical Stellar libraries limited by A good parameter coverage Synthetic Stellar libraries limits: Uncertainties in theoretical model atmospheres(non-local thermodynamic equilibrium (LTE), line blanketing, sphericity, expansion, non-radiative heating, convection etc )

  10. Synthetic Stellar Libraries for Gaia

  11. HRD Coverage

  12. BP/RP: 300-1100 nm, resolution 0.3 nm RVS: 840-890 nm, resolution 0.003 nm

  13. B-V Residuals to the empirical Calibrations by Worthey &Lee (2006)

  14. Residuals to Phoenix

  15. RVS resolution

  16. MARCS Library MARCS sample fluxes R=20000 Atmospheric band opacity sampling, i.e., the fluxes are exactly computed in a limitednumber (108,000) wavelength points at R=20000 Flux calibration problems

  17. MARCS synthetic spectra– STIS -- F9V [Fe/H]=-0.25 –[alpha/Fe]=0.1 IR Calibration problem

  18. OB STARS (TLUSTY) Spherically symmetric wind models -NLTE code. Wind models : ions of H, He, C, N, O, Ne, Si, P, S, and Fe. A total of over 43,000 bound-bound transitions are included. Radiative equilibrium. Comparison with FEROS delta Cet LTE for Teff < 15000 In early B dwarfs He I lines thinner –Stark Broadening underestimate? • Spectra in the RVS range, from TLUSTY models for O and B-type stars with log g =4.0. Teff ranges from 45,000 K down to 15,000 K (from top to bottom). The adopted metallicity is Z/Zsun = 1 (Bouret et al 2008) .

  19. SUMMARY As part of the GAIA project high resolution synthetic stellar libraries are calculated and compared with the observational data (V-I), (V-R) integrated colours are in good agrement with the observational calibrations For high resolution spectra: still a lot of work to be done

  20. Summary Gaia will need high quality spectra Large data bases of high resolution synthetic stellar spectra are calculated and compared with the data (V-I) ( V-R)Colours are reasonably in agreement with observational calibration High resolution MARCS sample fluxes are in poor agreement with data (but MARCS synthetic spectra are better performing)

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