Gaia : A new vision of the Galaxy3 Gaia: Complete, Faint, Accurate mardi 9 juillet 2013. Luri &...

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A.C. Robin et al., Institut UTINAM, Besançon, France 1 Gaia : A new vision of the Galaxy mardi 9 juillet 2013

Transcript of Gaia : A new vision of the Galaxy3 Gaia: Complete, Faint, Accurate mardi 9 juillet 2013. Luri &...

Page 1: Gaia : A new vision of the Galaxy3 Gaia: Complete, Faint, Accurate mardi 9 juillet 2013. Luri & Turon, 2011 mardi 9 juillet 2013. Estimating Gaia capabilities

A.C. Robin et al., Institut UTINAM, Besançon, France

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Gaia : A new vision of the Galaxy

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Gaia: Design Considerations

• Astrometry (V < 20):– completeness to 20 mag (on-board detection) ⇒ 109 stars– accuracy: 10–25 μarcsec at 15 mag (Hipparcos: 1 milliarcsec at 9 mag)– scanning satellite, two viewing directions

⇒ global accuracy, with optimal use of observing time– principle: global astrometric reduction (as for Hipparcos)

• Photometry (V < 20):– astrophysical diagnostics (low-dispersion photometry) + chromaticity

⇒ΔTeff ~ 200 K, log g, [Fe/H] to 0.2 dex, extinction

• Radial velocity (V < 17):– application:

• third component of space motion, perspective acceleration • dynamics, population studies, binaries• spectra for V < 14: chemistry, rotation

– principle: slitless spectroscopy in Ca triplet (847–874 nm) at R = 11,500

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Gaia: Complete, Faint, Accurate

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Luri & Turon, 2011

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Estimating Gaia capabilities

• Gaia «Universe Model» Snapshot

• Efficiencies and real capabilities

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GUMS: Gaia Universe Model Snapshot

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Robin A. C, Luri X., Reylé et al, A&A 2012 (CDS)

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Bulge:Crowding

VsNot reached !

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Density of stars in the final Gaia catalogue

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Stars in the MW ilky • Variability: (N.

Mowlavi, L. Eyer, CU7

21 x 106 variable stars

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Stars in the Milky Way

• Multiplicity and exoplanets: (F. Arenou)

410 x 106 binary systems

67% of primary stars are main sequence

62% of systems are a double main sequence system

30 % of systems are subgiants and giants as primary with a main sequence star

• Exoplanets: (A. Sozetti)

34 x 106 exoplanets

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Co lor sca le : log10 of number of objects per sq. deg.

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Uncertainties

From first tests done with software (GAIA-CU2-TN-UB-ELA-001-2 , Antiche, Luri & Borrachero, 2013)

Liu et al (MNRAS 426, 2463 (2012))

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Errors are correlated !

Liu et al, 201215

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Stellar Astrophysics • Comprehensive luminosity calibration, for example:

– distances to 1% for ~10 million stars to 2.5 kpc– distances to 10% for ~100 million stars to 25 kpc– rare stellar types and rapid evolutionary phases in large numbers– parallax calibration of all distance indicators

e.g., Cepheids and RR Lyrae to LMC/SMC

• Physical properties, for example:– clean Hertzsprung–Russell diagrams throughout the Galaxy– Solar-neighbourhood mass and luminosity function

e.g., white dwarfs (~400,000) and brown dwarfs (~50,000)– initial mass and luminosity functions in star-forming regions– luminosity function for pre-main-sequence stars– detection and dating of all spectral types and Galactic populations– detection and characterisation of variability for all spectral types

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Galactic expectations

• Stellar models :

• parallaxes for intrinsec luminosities

• Variables (distance calibrators, instability (stellar interiors)

• Binarity : rate vs population, semi-a distribution, m2/m1 distribution. Masses and radii

• Galactic dynamics : kinematics and distances (5D or 6D distribution functions)

• Chemo-dynamical evolution (metallicities to G~16-17, elemental abundances to G~12), whole sky !

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Parallaxes : at r=8 kpcat G=15 σπ=11.3 µas => Δr/r=9 % at G=17 σπ=28.5 µas => Δr/r=23 %

Proper motionsat G=17 σµ=21.4 µas/an σV=0.8 km/sat G=20 338. µas/an σV=12.8 km/s

Up to now: bulge kinematics at 40-50 km/s (Sumi et al.)‏

Radial velocities:Gaia: at V=14 : σV=25 km/s, at V=16 : σV=50 km/s

Bulge K giants

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Helmi et al 2007

Halo substructures (x,y,z) : dissolved in position, not in phase space

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Mass of the Galaxy : profil of the dispersion of radial velocitiesCompared with differents models of dark halo

Present uncertainty

1x 10 12

a factor of 2

Battaglia et al 2006

With Gaia :10% accuracy (Wilkinson, 2007)

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Gaia and the Local Group

• LMC-SMC : 7.5 millions and 1.5 millions of stars observable by Gaia

• Mean parallaxe error : 0.5% - 1.5% (from the mean of all observable stars)

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Gaia and the Local Group

• LMC-SMC : 7.5 millions and 1.5 millions of stars observable by Gaia

• Mean parallaxe error : 0.5% - 1.5% (from the mean of all observable stars)

Cepheids and bright objects => 3D distribution of the MC

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Dwarfs spheroidals

• Limited by the limiting magnitude of Gaia G<20

• But indirect measurements for improving our knowledge about the Local Group

• Better understanding of stellar evolution/stellar models (via masses in binaries, and absolute magnitudes via parallaxes) => improved isochrones

• Variable stars and the distance scale

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Conclusions• A lot of expectations

• Final accuracies to be defined by real data

• Launch : 19th septembre (TBC)

• Release plan : GAIA-C9-TN-ESAC-WOM-066-02 (OʼMullane et al)

• First release : L+22 months : positions and G magnitude for single stars (90% of sky), HTPM (wth Hipparcos)

• 2nd release : L+28 months : + BP/RP + AP+RV (single *, cste RV, no problems) 90% sky

• 3rd release : L+40 months : + AP + orbits + source classifications

• Other releases : photometric alerts, NEO alerts...

• Epoch data, transits: end of mission (5th release)

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