Gaia : A new vision of the Galaxy3 Gaia: Complete, Faint, Accurate mardi 9 juillet 2013. Luri &...
Transcript of Gaia : A new vision of the Galaxy3 Gaia: Complete, Faint, Accurate mardi 9 juillet 2013. Luri &...
A.C. Robin et al., Institut UTINAM, Besançon, France
1
Gaia : A new vision of the Galaxy
mardi 9 juillet 2013
2
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
mardi 9 juillet 2013
3
Gaia: Complete, Faint, Accurate
mardi 9 juillet 2013
Luri & Turon, 2011
mardi 9 juillet 2013
Estimating Gaia capabilities
• Gaia «Universe Model» Snapshot
• Efficiencies and real capabilities
5mardi 9 juillet 2013
GUMS: Gaia Universe Model Snapshot
6
Robin A. C, Luri X., Reylé et al, A&A 2012 (CDS)
mardi 9 juillet 2013
7
Bulge:Crowding
VsNot reached !
mardi 9 juillet 2013
Density of stars in the final Gaia catalogue
mardi 9 juillet 2013
mardi 9 juillet 2013
Stars in the MW ilky • Variability: (N.
Mowlavi, L. Eyer, CU7
21 x 106 variable stars
10mardi 9 juillet 2013
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
11mardi 9 juillet 2013
Co lor sca le : log10 of number of objects per sq. deg.
12mardi 9 juillet 2013
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))
13mardi 9 juillet 2013
14mardi 9 juillet 2013
Errors are correlated !
Liu et al, 201215
mardi 9 juillet 2013
16
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
mardi 9 juillet 2013
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 !
17mardi 9 juillet 2013
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
mardi 9 juillet 2013
Helmi et al 2007
Halo substructures (x,y,z) : dissolved in position, not in phase space
mardi 9 juillet 2013
mardi 9 juillet 2013
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)
mardi 9 juillet 2013
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)
mardi 9 juillet 2013
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
mardi 9 juillet 2013
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
mardi 9 juillet 2013
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)
24mardi 9 juillet 2013