sait teramo – may 6 th, 2008 antonella vallenari spectral libraries for gaia synthetic spectral...

SaitTeramo – May 6th, 2008

Antonella VallenariSpectral Libraries for Gaia

Synthetic Spectral Libraries for Gaia

A. VallenariINAF, Osservatorio Astronomico di Padova



On behalf of Gaia Classification Unit

OAPD peopleR.SordoG.BertelliE.NasiU.MunariC.ChiosiR.Tantalo

Collaborators: Edvardsson, Gustafsson, Korn, Heiter (Uppsala Univ)deLaverny, Recio-Blanco, Thevenin (OCA)GHOST team: Bouret, LanzKochukov, ShulyakFremat, Zorec, MartinsC. Bailer-Jones (MPIA Heidelberg)M.Kontizas (Athens Univ)A. Lanzafame ( Catania Univ.)

and others



GALACTIC SURVEY



Final Catalog and Classification problemThe Catalog will include astrometric APs and basic APs for starsNo 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!

–



Classification scheme



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



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



DATA BASES FOR GAIAsynthetic / observational stellar spectra : (Sordo Munari et al 2005)

The Asiago Database on Photometric Systems (ADPS) and spectra 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



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 )



OB stars GHOST group 500000-150000 K TLUSTY- NLTE and LTE

A stars (Kurucz) GHOST group 15000-8000 K Solar scaled,

[Fe/H]=-5 - - 1

C Montpellier Group

Josselin & Plez

8000-4000MARCS, [C/Fe]= 0,1,2,3

WD ( WDA-WDB) Koester 70000-5000 K LTE

Be (e) Fremat & Zorec B+ emission

WR (e) F.Martins OB+ emission

A normal

and with anomalies

Kochukhov 15000-6000 K [Fe/H]=0

SrCrEu & Si; HgMn

A0-M Normal Phoenix 10000-3000 K LTE, alpha enhanc.

Ultra-Cool dwarf Allard 3000-1000 K

Supergiants- normal Josselin 5000-3000 K

A5,F,G,K MARCS Photospheric samples + spectra

8000-4000 K Ca, O, Mg, Si, Fe

Synthetic Stellar Libraries for Gaia



HRD Coverage


Antonella VallenariSpectral Libraries for Gaia • BP/RP: 300-1100 nm, resolution 0.3 nm

• RVS: 840-890 nm, resolution 0.003 nm



Residuals to the empirical Calibrations by Worthey &Lee (2006)

B-V



Residuals to Phoenix



RVS resolution



MARCS Library

MARCS sample fluxes R=20000

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

Atmosphericband



MARCS synthetic spectra– STIS -- F9V [Fe/H]=-0.25 –[alpha/Fe]=0.1

IR Calibration problem



• 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 CetLTE for Teff < 15000In early B dwarfs He I lines thinner –Stark Broadening underestimate?



• 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



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)

sait teramo – may 6 th, 2008 antonella vallenari spectral libraries for gaia synthetic spectral...

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