1. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Synthetic Spectral Libraries for Gaia A.Vallenari INAF, Osservatorio Astronomico di Padova

2. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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) A.Lanzafame ( Catania Univ.) and others

3. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia GALACTIC SURVEY

4. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Gaia sees 10 9 objects about 80 times. Gaia produces an unprecedented volume of data, 40 to 50 GB every day for 5 years leading to almost 100 TB of compressed data. Data reduction is a challenge Number of transits

5. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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 10 9 objects to G=20 is ill-defined! –

6. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Classification scheme

7. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia How stellar parameters may be derived from the Gaia data.

8. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Precision of AP estimates from RP/BP at G=15 (end-of-mission noise level). Each panel plots the standard deviation of residuals versus the logarithm of the (true) temperature. Results are shows for four groups with metallicities of [Fe/H]high =[0,1] dex, [Fe/H]mid [-1.5 0] [ [Fe/H]low [-3,-1.5] [-3,-5]

9. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia HOT (12 000 K Teff 40 000 K), MEDIUM (8000 K Teff 12 000 K) and COOL (3000 K Teff 6000 K) Precision estimate – multilinear regression algorithm

10. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia

11. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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

12. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia DATA BASES FOR GAIA synthetic / observational stellar spectra : (Sordo Munari et al 2005) The Asiago Database on Photometric Systems (ADPS) and spectra http://archives.pd.astro.it/2500-10500 / http://archives.pd.astro.it/2500-10500 / synthetic/observational galaxy 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

13. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Synthetic versus Empirical stellar Libraries Refined high resolution stellar spectra are of fundamental importance in the Gaia era, first to predict the response of the instruments and then to interprete the observations In the literature, both empirical & theoretical libraries are 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 )

14. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Comparison of the SED’s of 6 stars in the IndoUS and MILES stellar libraries in the wavelength range 3500-7400 Å. The green line represent the difference (IndoUS-Miles) (Bruzual 2006) Empirical Libraries HNGSL: Hubble’s New Generation Stellar Library (Heap and Lanz 2003, Gregg et al 2004): 2000 to 10,000 Å for 400 stars. Low resolution, but UV coverage (resolution 5 A). UVES POP Library: UVES Paranal Observatory Project – (Bagnulo et al. 2004). High SNR spectra from 3040 to 10,400 Å for over 400 stars, with R = 80,000. ELODIE: 2000 stars observed with the échelle spectrograph (ELODIE) at the OHP, R = 42,000 from 4000 to 6800 Å (Prugniel & Soubiran 2004). Indo–US Library: A library of KPNO stellar spectra (Valdes et al. 2004) for 1273 stars from 3460 to 9464 Å resolution of ~ 1Å. MILES: spectra for ~ 1000 stars with 2.4 Å resolution in the range from 3500 to 7500 Å (Sánchez- Blázquez et al. 2006). (resolution 2.3 A) STELIB 249 stars, range 3200-9500 A at 3A

15. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia OB stars GHOST group500000-150000 K TLUSTY- NLTE and LTE A stars (Kurucz) GHOST group15000-8000 K Solar scaled, [Fe/H]=-5 - - 1 C Montpellier Group Josselin & Plez 8000-4000 MARCS, [C/Fe]= 0,1,2,3 WD ( WDA-WDB) Koester70000-5000 K LTE Be (e) Fremat & ZorecB+ emission WR (e) F.MartinsOB+ emission A normal and with anomalies Kochukhov15000-6000 K [Fe/H]=0 SrCrEu & Si; HgMn A0-M Normal Phoenix10000-3000 K LTE, alpha enhanc. Ultra-Cool dwarf Allard3000-1000 K Supergiants- normal Josselin5000-3000 K A5,F,G,K MARCS Photospheric samples + spectra 8000-4000 K Ca, O, Mg, Si, Fe Synthetic Stellar Libraries for Gaia

16. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia HRD Coverage

17. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia BP/RP: 300-1100 nm, resolution 0.3 nm RVS: 840-890 nm, resolution 0.003 nm

18. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Residuals to the empirical Calibrations by Worthey &Lee (2006) B-V

19. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Residuals to Phoenix

20. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia

21. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia RVS resolution Residuals to Coelho

22. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia RVS resolution

23. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia

24. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia MARCS Library MARCS sample fluxes R=20000 opacity sampling, i.e., the fluxes are exactly computed in a limited number (108,000) wavelength points at R=20000 Flux calibration problems Atmospheric band

25. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia MARCS synthetic spectra– STIS -- F9V [Fe/H]=-0.25 –[alpha/Fe]=0.1 IR Calibration problem

26. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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). 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. OB STARS (TLUSTY) Comparison with FEROS delta Cet LTE for Teff < 15000 In early B dwarfs He I lines thinner –Stark Broadening underestimate?

27. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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

28. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia 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)

29. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Synthetic Libraries Amongst the synthetic libraries we quote: the Basel Stellar Library (BaSeL) (Lejeune, Cuisinier & Buser 1997, 1998; Westera et al. 2002) based on Kurucz (1993) models but including spectra of M stars computed with model atmospheres by Bessell et al. (1989, 1991), Fluks et al. (1994) and Allard & Hauschildt (1995). However, the spectral resolution of the BaSeL library is limited to 20 Å, which is lower than the observed spectra of both individual stars and integrated stellar populations. High resolution libraries are: Chávez, Bertone, Buzzoni, Rodríguez-Merino: Atlas from 850 to 4750 Å for same parameters as Kurucz model atmospheres. Designed to study UV spectral indices. González-Delgado & Cerviño: Atlas from 3000 to 7000 Å for an ample range of parameters. Zwitter Munari & Castelli (2004):include effects of alpha enhancement in an atlas from 3000 to 10000 Å at high resolution. Coelho et al. (2005) theoretical model atmospheres: based on Kurucz original models but at high resolution (0.1 Å) in the optical and IR. (see Coelho et al. 2004) including alpha enhancement Gustafsson et al. 2003 MARCS from 3000 K to 8000 K for a wide range of metallicity and alpha enhancements Brott & Hauschildt 2005 PHOENIX

30. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Main Limitations of Empirical Stellar Libraries Empirical Stellar libraries limits are: A good parameter coverage is not trivial for empirical libraries. They have to cover : a good wavelength range (which limits the spectral resolution) good spectral type coverage, from cool to hot stars, dwarfs and giants and different chemical abundances. Uncertainties on the absolute flux calibration scale

31. Sait Teramo – May 6 th, 2008 Antonella Vallenari Spectral Libraries for Gaia Main Limitations of Synthetic Stellar Libraries Spectral wavelength coverage and resolutions Coverage of HRD or CMD Metallicity coverage Uncertainties in theoretical model atmospheres (non-local thermodynamic equilibrium (LTE), line blanketing, sphericity, expansion, non-radiative heating, convection etc ). The most difficult stars in this sense are the very hot and very cool stars, where extreme scenarios take place (e.g. non-LTE effects for very hot stars, and sphericity for cool giants). Additionally, computing reliable high-resolution synthetic spectra is a very challenging task, since it requires building an extensive and accurate list of atomic and molecular line opacities. Flux calibration or lack of it