gaia unraveling the chemical and dynamical history of our galaxy
DESCRIPTION
G aia A Stereoscopic Census of our Galaxy & Czech Participation http://www.rssd.esa.int/Gaia IBWS October 25-28, 2006. Gaia Unraveling the chemical and dynamical history of our Galaxy. Gaia: Design Considerations. Astrometry (V < 20): - PowerPoint PPT PresentationTRANSCRIPT
Gaia A Stereoscopic Census of our Galaxy &
Czech Participation
http://www.rssd.esa.int/Gaia
IBWS October 25-28, 2006
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Gaia
Unraveling the chemical and dynamical history of our 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– principles: global astrometric reduction (as for Hipparcos)
• Photometry (V < 20):– astrophysical diagnostics (low-dispersion photometry) + chromaticity
Teff ~ 200 K, log g, [Fe/H] to 0.2 dex, extinction
• Radial velocity (V < 16–17):– application:
• third component of space motion, perspective acceleration• dynamics, population studies, binaries• spectra: chemistry, rotation
– principles: slitless spectroscopy using Ca triplet (847–874 nm)
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Gaia: Complete, Faint, Accurate
Hipparcos Gaia
Magnitude limit 12 20 mag Completeness 7.3 – 9.0 20 mag Bright limit 0 6 mag Number of objects 120 000 26 million to V = 15 250 million to V = 18 1000 million to V = 20 Effective distance limit
1 kpc 1 Mpc Quasars None 5 x 105
Galaxies None 106 – 107 Accuracy 1 milliarcsec 7 µarcsec at V = 10 10-25 µarcsec at V = 15 300 µarcsec at V = 20 Photometry photometry
2-colour (B and V) Low-res. spectra to V = 20 Radial velocity None 15 km/s to V = 16-17 Observing programme
Pre-selected Complete and unbiased
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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 function and luminosity function
e.g. white dwarfs (~200,000) 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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One Billion Stars in 3-d will Provide …
• in our Galaxy …– the distance and velocity distributions of all stellar populations
– the spatial and dynamic structure of the disk and halo
– its formation history
– a rigorous framework for stellar structure and evolution theories
– a large-scale survey of extra-solar planets (~10–20,000)
– a large-scale survey of Solar System bodies (~100,000)
– support to developments such as VLT, JWST, etc.
• … and beyond– definitive distance standards out to the LMC/SMC
– rapid reaction alerts for supernovae and burst sources (~20,000)
– QSO detection, redshifts, microlensing structure (~500,000)
– fundamental quantities to unprecedented accuracy: to 10-7 (10-5 present)
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Planète : = 100 mas P = 18 mois
Exo-Planets: Expected Discoveries
• Astrometric survey:– monitoring of hundreds of thousands of FGK stars to ~200 pc
– detection limits: ~1MJ and P < 10 years
– complete census of all stellar types, P = 2–9 years
– masses, rather than lower limits (m sin i)
– multiple systems measurable, giving relative inclinations
• Results expected:– 10–20,000 exo-planets (~10 per day)
– displacement for 47 UMa = 360 μas
– orbits for ~5000 systems
– masses down to 10 MEarth to 10 pc
• Photometric transits: ~5000?
Figure courtesy François Mignard
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• Asteroids etc.:– deep and uniform (20 mag) detection of all moving objects
– 105–106 new objects expected (340,000 presently)
– taxonomy/mineralogical composition versus heliocentric distance
– diameters for ~1000, masses for ~100
– orbits: 30 times better than present, even after 100 years
– Trojan companions of Mars, Earth and Venus
– Kuiper Belt objects: ~300 to 20 mag (binarity, Plutinos)
• Near-Earth Objects: – Amors, Apollos and Atens (1775, 2020, 336 known today) – ~1600 Earth-crossers >1 km predicted (100 currently known)– detection limit: 260–590 m at 1 AU, depending on albedo
Gaia: Studies of the Solar System
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Light Bending in Solar System
Movie courtesy Jos de Bruijne
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Satellite and System
• ESA-only mission• Launch date: 2011 • Lifetime: 5 years• Launcher: Soyuz–Fregat from CSG• Orbit: L2• Ground station: New Norcia and/or Cebreros• Downlink rate: 4–8 Mbps
• Mass: 2030 kg (payload 690 kg)• Power: 1720 W (payload 830 W)
Figures courtesy EADS-Astrium
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Payload and Telescope
Two SiC primary mirrors1.45 0.50 m2 at 106.5°
SiC toroidalstructure
(optical bench)
Basic anglemonitoring system
Combinedfocal plane
(CCDs)
Rotation axis (6 h)
Figure courtesy EADS-Astrium
Superposition of two Fields of View
(FoV)
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Focal Plane
Star motion in 10 s
Total field: - active area: 0.75 deg2
- CCDs: 14 + 62 + 14 + 12 - 4500 x 1966 pixels (TDI) - pixel size = 10 µm x 30 µm
= 59 mas x 177 mas
Astrometric Field CCDs
Blue P
hotometer C
CD
s
Sky Mapper CCDs
104.26cm
Red P
hotometer C
CD
s Radial-Velocity Spectrometer
CCDs
Basic Angle
Monitor
Wave Front Sensor
Basic Angle
Monitor
Wave Front Sensor
Sky mapper: - detects all objects to 20 mag - rejects cosmic-ray events - FoV discriminationAstrometry: - total detection noise: 6 e-
Photometry: - two-channel photometer - blue and red CCDsSpectroscopy: - high-resolution spectra - red CCDs
42.3
5cm
Figure courtesy Alex Short
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On-Board Object Detection• Requirements:
– unbiased sky sampling (mag, colour, resolution)
– no all-sky catalogue at Gaia resolution (0.1 arcsec) to V~20
• Solution: on-board detection:– no input catalogue or observing programme
– good detection efficiency to V~21 mag
– low false-detection rate, even at high star densities
• Will therefore detect:– variable stars (eclipsing binaries, Cepheids, etc.)
– supernovae: 20,000
– microlensing events: ~1000 photometric; ~100 astrometric
– Solar System objects, including near-Earth asteroids and KBOs
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Sky Scanning Principle
Spin axis 45o to SunScan rate: 60 arcsec/sSpin period: 6 hours
45o
Figure courtesy Karen O’Flaherty
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Comments on Astrometric Accuracy
• Massive leap from Hipparcos to Gaia:– accuracy: 2 orders of magnitude (1 milliarcsec to 7 microarcsec)– limiting sensitivity: 4 orders of magnitude (~10 mag to 20 mag)– number of stars: 4 orders of magnitude (105 to 109)
• Measurement principles identical:– two viewing directions (absolute parallaxes)– sky scanning over 5 years parallaxes and proper motions
• Instrument improvement:– larger primary mirror: 0.3 0.3 m2 1.45 0.50 m2, D-(3/2)
– improved detector (IDT CCD): QE, bandpass, multiplexing
• Control of all associated error sources:– aberrations, chromaticity, solar system ephemerides, attitude control …
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Photometry Measurement Concept (1/2)
Figures courtesy EADS-Astrium
Blue photometer:330–680 nm
Red photometer:640–1000 nm
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Photometry Measurement Concept (2/2)
Figures courtesy Anthony Brown
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RP spectrum of M dwarf (V=17.3)Red box: data sent to ground
White contour: sky-background levelColour coding: signal intensity
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Spectroscopy:847–874 nm
(resolution 11,500)
Radial Velocity Measurement Concept (1/2)
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Radial Velocity Measurement Concept (2/2)
RVS spectra of F3 giant (V=16) S/N = 7 (single measurement)
S/N = 130 (summed over mission)
Field of view RVS spectrograph CCD detectors
Figures courtesy David Katz
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Data Reduction Principles
Sky scans(highest accuracy
along scan)
Scan width: 0.7°
1. Object matching in successive scans2. Attitude and calibrations are updated3. Objects positions etc. are solved4. Higher terms are solved5. More scans are added6. System is iteratedFigure courtesy Michael Perryman
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Scientific Organisation
• Gaia Science Team (GST): – 12 members + ESA Project Scientist
• Scientific community:– organised in Data Processing and Analysis Consortium (DPAC)– ~270 scientists active at some level
• Community is active and productive:– regular science team/DPAC meetings– growing archive of scientific reports– advance of simulations, algorithms, accuracy models, etc.
• Data distribution policy:– final catalogue ~2019–20– intermediate catalogues as appropriate– science alerts data released immediately– no proprietary data rights
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Ingestion, preprocessing,data base + versions,
astrometric iterative solutionESAC (+ Barcelona + OATo)
Object processing(shell tasks)
+ ClassificationCNES, Toulouse
PhotometryCambridge (IOC)
+ VariabilityGeneva (ISDC)
Spectroscopicprocessing
CNES, Toulouse
Overall system architecture
ESACData simulations
Barcelona
From ground station
Community access
Data Processing Concept (simplified)
Status and contributions to be confirmed
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Status and Schedule
• Prime contractor: EADS-Astrium– implementation phase started early 2006
• Main activities and challenges:– CCDs and FPA (including PEM electronics)– SiC primary mirror– high-stability optical bench– payload data handling electronics– phased-array antenna– micro-propulsion– scientific calibration of CCD radiation-damage effects
• Schedule:– no major identified uncertainties to affect cost or launch schedule– launch in 2011– technology/science ‘window’: 2010–12
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Schedule
Catalogue
2000 2004 2008 2012 2016 2020
ESA acceptance
Technology Development
Design, Build, Test
Launch
Observations
Data Analysis
Early Data
Concept & Technology Study (ESA)
Re-assessment:Ariane-5 Soyuz
Cruise to L2
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Participation of Ondrejov HEA team
Focuses on Gaia CU7 Variability Processing
Natural Extension of Czech participation in INTEGRAL ISDC
Two work packages accepted on CVs and Optical counterparts of High energy sources
Additional participation in image processing – recently algorithms designed of scanned
Schmidt spectral plates – simulation of Gaia data
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Simulated low dispersion Gaia spectrum
Real low dispersion spectrum from digitised Schmidt spectral plate
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Czech Participation II
• another part of the Czech Gaia participation will focus on direct participation in Gaia CU7 DPC Data Processing Center
• Participation in software development in a team, Java, object oriented programming
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The End