GAIA Composition, Formation and Evolution of our Galaxy : GAIA Composition, Formation and Evolution of our Galaxy thanks to Michael Perryman, the GAIA Science
Team (present and past) and 200+ others
M83 image (with Sun marked) : M83 image (with Sun marked) M83 (AAO, D. Malin)
GAIA: Key science objectives : GAIA: Key science objectives Structure and kinematics of our Galaxy:
shape and rotation of bulge, disk and halo
internal motions of star forming regions, clusters, etc
nature of spiral arms and the stellar warp
space motions of all Galactic satellite systems
Stellar populations:
physical characteristics of all Galactic components
initial mass function, binaries, chemical evolution
star formation histories
Tests of galaxy formation:
dynamical determination of dark matter distribution
reconstruction of merger and accretion history
Origin, Formation and Evolution of the Galaxy
Overview : Overview Measurement principles
The GAIA satellite and mission
Some science examples
Schedule, organisation of work
Current situation
Summary
Some history… : Some history… 1725: Stellar aberration (Bradley), confirming:
Earth’s motion through space
finite velocity of light
immensity of stellar distances 125 B.C.: Precession of the equinoxes (Hipparchus) 1717: First proper motions (Halley) 1783: Sun’s motion through space (Herschel) 1838-9: First parallaxes (Bessel/Henderson/Struve) 610 B.C.: Obliquity of the ecliptic (Anaximander) 1761/9: Transits of Venus across the Sun (various)
solar parallax
Principle of parallax measurement : Principle of parallax measurement
Astrometry from antiquity to GAIA : Astrometry from antiquity to GAIA
Hipparcos : Hipparcos ESA mission
1989 – 1993 (catalogue in 1997)
120 000 stars in 2 filters
Limiting magnitude: V=12.4
Complete to V=7.3 to 9.0
Median precisions (Hp<9.0):
0.7 mas positional
0.7 mas/yr
1.0 parallax
Distance <10%: 21 000
Distance <20%: 50 000
Tycho (star mapper):
1 000 000 stars in 2 filters
7 mas (Hp<9.0)
Slide9 : Measurement Principle
Measurement principle: b : Measurement principle: b
Global astrometry : Global astrometry basic angle
Measurement principle: c : Measurement principle: c
GAIA: complete, faint, accurate : GAIA: complete, faint, accurate
Scientific design considerations : Scientific design considerations Astrometry (V < 20):
completeness on-board detection
accuracies: 10 as at 15 mag (science)
continuously scanning satellite, two viewing directions
global accuracy, optimal with respect to observing time
Radial velocity (V < 17-18):
third component of space motion
account for perspective acceleration (nearby, fast stars)
Photometry (V < 20):
astrophysical diagnostics (4-band + 11-band) + chromatic correction
extinction, Teff ~ 200 K, [Fe/H] to 0.2 dex
Satellite : Satellite Deployable: solar array/sun-shield
Size: 8.5m diameter (4.2m stowed)
2.9m height (2.1m for payload)
Mass: 3100 kg (800 kg payload)
Power: 2600 W
Launch: dual Ariane 5
Orbit: Sun-Earth L2 (Lissajous)
Data rate (phased array):
1 Mbs-1 sustained
3 Mbs-1 downlink (1 ground station)
Launch date: 2010-12
Attitude control: FEEP thrusters
Design lifetime: 5 years
ESA only mission
Payload overview : Payload overview Two astrometric instruments:
field of view = 0.6o 0.6o
separation = 106o
Monolithic mirrors: 1.7 m 0.7 m
Non-deployable, 3-mirror, SiC optics
Astrometric focal planes: TDI CCDs
Radial velocity/photometry telescope
Survey principles:
revolving scanning
onboard detection
complete and unbiased sample
Payload configuration : Payload configuration
Slide18 : Astrometric instrument: Light path 1 2 3 4
Astrometric focal plane : Astrometric focal plane Sky mapper:
- detects all objects to 20 mag
- rejects cosmic-ray hits
- mag + x,y to main field
Main field:
- area: 0.66 x 0.56 deg = 0.37 deg2
- size: 60 70 cm2
- number of CCDs: 17 x 8=136
- CCDs: 2780 x 2150 pixels
- 120´´/s 0.86s per CCD
Pixels:
- size: 9 x 27 m2 (37 x 111 mas)
- read in TDI mode
Broad-band photometry:
- 4 band (chromatic correction)
On-board source detection : On-board source detection Requirements and constraints:
unbiased sky sampling (mag, colour, resolution, etc.)
no all-sky catalogue at GAIA resolution (0.1 arcsec) to V~20
cannot transmit entire sky at 0.1 arcsec resolution (telemetry limitations)
Solution: on-board detection and sampling
no input catalogue or observing programme (big effort for Hipparcos)
good detection efficiency to V~21 mag
maximum star density: ~ 3 million stars/deg2 (Baade’s Window)
reduces data rate from several Gbps to a few Mbps
Will therefore also detect:
supernovae: 105 expected
microlensing events: ~1000 photometric
variable stars (eclipsing binaries, Cepheids, etc)
Solar System objects, including near-Earth asteroids and KBOs
Sky scanning principle : Sky scanning principle Spin axis: 55o to Sun
Scan rate: 120 ´´/s
(3 hours)
Precession rate: 0.20 ´´/s
(76 days)
Continuously observing
Full sky coverage
Each position observed
67 times (on average) per astrometric instrument
Scanning law : Scanning law Observations over 5 months Ecliptic co-ordinates
Astrometric accuracies : Astrometric accuracies Derived from detailed analysis:
image formation (polychromatic PSF)
evaluation vs. spectral type/reddening
comprehensive detector signal model
sky background and image saturation
attitude rate errors and sky scanning
on-board detection probability
on-ground location estimation
(centroid to 0.001 pixel in hardest case)
error margin of 20 per cent included
results folded with Galaxy model Fraction of stars with given relative parallax
error vs. magnitude (towards Galactic poles) 5-year
accuracies
in as
Accuracy example: Stars at 15 mag with / 0.02 : Accuracy example: Stars at 15 mag with / 0.02
CCD centroiding tests : CCD centroiding tests Astrium contract (Sep 2000)
‘GAIA-mode’ operation
EEV CCD 42-10
13m pixels
Illumination: 240,000 e-
Frequencies:
TDI: 2.43 kHz
Readout: 90 kHz
Differential centroid errors:
rms = 0.0038 pixels
(1.2 theoretical limit)
Survey accuracies compared : Survey accuracies compared
1 as is a very small angle ... : 1 as is a very small angle ... the Earth seen from the Pleiades (100 pc) Baden-Württemberg seen from Centauri (1.3 pc) a human hair observed in Kabul from Heidelberg (5000 km) Earth-Sun system seen from 1 Mpc (by definition) a grain of rice seen on the Moon (380 000 km)
Design requirements : Design requirements Need to monitor basic angle variations to 1 as:
25 K thermal gradients
16 pm peak-to-peak variation over 0.85m
onboard interferometer
High thermal and mechanical stability:
no moving parts (electronically steerable phased array)
L2 orbit (dynamical stability, eclipse avoidance, low radiation)
Astrometric reduction : Astrometric reduction Approximate single epoch astrometry (<<1´´) from star mapper and GAIA orbit/attitude
Great circle scans 1D positions in two fields separated by a well-known basic angle (monitored)
Object matching in different scans (e.g. GSC II method)
Full sphere reduction to determine 5 astrometric parameters per star by a global iterative method (>100 measures)
Binary models fitted to systems with large residuals
GAIA observations of quasars (known and new) put the astrometry on a quasi-inertial reference system
Object matching : Object matching Sky scan
(highest accuracy
along scan)
GAIA spectrophotometry and radial velocities : GAIA spectrophotometry and radial velocities High resolution spectra for:
- 3rd component of space motion
- perspective acceleration
- stellar abundances, rotation velocities
Medium band photometer for:
- classification of all objects
- physical parametrization of stars
Teff, log g, [Fe/H], [/H], A()
Radial Velocity Measurement Concept : Radial Velocity Measurement Concept F3 giant
S/N = 7 (single measurement)
S/N = 130 (summed over mission)
Slide36 : Radial Velocity and Photometric Instrument Mounted on same toroidal support
Observes same scanning circles
Independent star mappers
Photometry for all stars (to 20 mag)
Radial velocities to ~ 18 mag
1-10 km/s accuracy
0.5´´ spatial resolution
Spectral Sequences around Ca II : Spectral Sequences around Ca II Effect of temperature: A to M stars Effect of metal abundance in G stars
Photometric system and accuracies : Photometric system and accuracies 11 medium band (in Spectro, 100 obs.)
4 broad band filters (in Astro, 2x67 obs.)
SNR: 100-500 at V=15 (10-100 at V=20)
(end of mission) F33 B45 B63 B82
Slide39 : GAIA and our Galaxy 10 as = 10% distances at 10 kpc 10 as/yr = 1 km/sec at 20 kpc
GAIA: Why a survey to 20 mag? : GAIA: Why a survey to 20 mag?
GAIA capabilities : GAIA capabilities Distances:
<0.1% for 700 000 stars <1% for 21 million <10% for 220 million
Transverse motions:
<0.5% km/s for 44 million <3 km/s for 210 million <10 km/s for 440 million
Radial velocities to a few km/s complete to V=17-18
15-band photometry (250-950nm) at ~100 epochs over 4 years
Complete survey of the sky to V=20, observing 109 objects:
108 binary star systems (detected astrometrically; 105 orbits)
200 000 disk white dwarfs
50 000 brown dwarfs
50 000 planetary systems
106-107 resolved galaxies
105 quasars
105 extragalactic supernovae
105-106 Solar System objects (65 000 presently known)
Stellar astrophysics : Stellar astrophysics Comprehensive luminosity calibration, for example:
distances to 1% for 18 million stars to 2.5 kpc
distances to 10% for 150 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 sequences 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 the oldest (disk and halo) white dwarfs
Binary and multiple stars : Binary and multiple stars Constraints on star formation theories
Orbits for > 100,000 resolved binaries (separation > 20 mas)
Masses to 1% for > 10,000 objects throughout HR diagram
Full range of separations and mass ratios
Interacting systems, brown dwarf and planetary companions
Photocentric motions:
~108 binaries
Photometry:
>106 eclipsing binaries
Radial velocities:
>106 spectroscopic binaries
Brown dwarfs : Brown dwarfs Isolated systems (Haywood, Les Houches 2001):
very red very few objects (photometry limited by CCD physics)
detections at G=20 mag sensitive to models (slope of IMF):
= 1: ~3000-5000 objects (also from 2MASS constraints)
sampling biased to very young and massive BDs (<100 pc):
10% with M<0.05 Ms; ~50% with age < 1 Gyr
Binary systems (Quist, A&A 2001, 370, 672):
many to 100pc with P=0.01-200 yr will be detected
orbital solutions for P < 15 yr
from 280,000 primaries to 100pc, expect ~3000
Slide45 : Exosolar planets: Detection domains No sin i ambiguity
in mass
determination
from astrometry
Slide46 : Known planetary orbits
Slide47 : Planets: astrometric signatures …. in arcsec if a in AU
and d in pc
Slide48 : Sampled orbits
simulated
for GAIA
47 UMa
(Lattanzi et al. 2000)
Slide49 : Multiple systems seen
with GAIA: And
(Sozzetti et al. astro-ph/0104391)
- relative inclination important
for stability
- Vrad does not give i or
And B (P=4.6 d) undetected
C (241 d) and D (1200 d) detected
For large and well sampled P
(<5 years) Mp and i are found
as if single, hence:
coplanarity to a few degrees
Expected astrometric planetary discoveries : Expected astrometric planetary discoveries Monitoring of hundreds of thousands of stars to 200 pc for 1MJ planets with P < 10 years:
complete census of all stellar types (P=2-9 years)
actual masses, not just lower limits (m sin i)
20,000-30,000 planets expected to 150-200 pc
e.g. 47 UMa: astrometric displacement 360 as
Orbits for many (~ 5000) systems
Masses down to 10 MEarth to 10 pc
Solar System objects: Detection principles : Solar System objects: Detection principles ASM1 ASM3 AF1 AF2 AF3 AF17 …….. Star NEO Detection to V = 20 mag and SAA 35-145o
At 300 arcsec/s moves by 1.2 arcsec in 15 s Sky Mapper Astrometric Field Detection Confirmation 2.2 1.3
arcsec2 0.22 0.89
arcsec2
Slide52 : The Inner Solar System Jupiter Trojans (610)
numbered periodic comets
other comets minor planets (numbered/multiple apparition)
perihelia < 1.3 AU
GAIA: Studies of the Solar System : Deep and uniform detection of all moving objects:
complete to 20 mag
discovery of ~105 - 106 new objects (cf. 65,000 presently)
taxonomy and mineralogical composition versus heliocentric distance
diameters for ~1000 asteroids
masses for ~100 objects
orbits: 30 times better than present, even after 100 years
Trojan companions of Mars, Earth and Venus
Edgeworth-Kuiper Belt objects: ~300 to 20 mag + binarity + Plutinos
Near-Earth Objects:
~1600 Earth-crossing asteroids > 1 km (100 currently known)
GAIA detection: 260 - 590 m at 1 AU, depending on albedo GAIA: Studies of the Solar System
Solar eclipse (image) : Solar eclipse (image) General Relativity (light bending)
Light Bending at L2 by solar system bodies : Light Bending at L2 by solar system bodies Klioner (2002)
de Bruijne (2002)
Gravitational light deflection : Gravitational light deflection de Bruijne (2002)
General Relativity : General Relativity Parametrized Post-Newtonian (PPN) formulation
= 1.0 for General Relativity (GR)
alternative scalar-tensor theories deviate by 10-5- 10-7
GAIA will measure to 510-7 from positional displacement at large angles from the Sun
currently known to 10-5
GAIA tests GR at 10-100 times lower mass than presently
effect of Sun: 4 mas at 90o; Jovian limb: 17 mas; Earth: 40 as
Microlensing: photometric (~1000) and astrometric (few) events
Galaxies, quasars, and the reference frame : Galaxies, quasars, and the reference frame Parallax distances, orbits, and internal dynamics of nearby galaxies
Galaxy survey (106-107 resolved at 0.1´´ in four bands, 0.5´´ in 11 bands)
~500,000 quasars: kinematic and photometric detection
~100,000 supernovae
Galactocentric acceleration: 0.2 nm/s2 (aberration) = 4 as/yr
Globally accurate reference frame to ~0.4 as/yr
Schedule : Schedule 2000 2004 2008 2012 2016 2020 Acceptance Technology Development Design, Build, Test Launch Observations Analysis Catalogue
Future schedule : Future schedule 2001-03: Phase A technical preparatory study:
study of critical items identified during concept study
(focal plane, CCDs, SiC mirrors, data handling, etc)
objective: confidence in technology, cost, schedule
end 2003: scientific and technical report
2005-2006: Phase B detailed design
2006-2010: Phase C/D construction and launch
mid-2012: launch (formally)
ESA target date: mid-2011
community target: mid-2010
Cost at completion : Cost at completion
Slide62 : High performance, small pixel (9 m) CCDs
Focal plane assembly and verification; on-board detection
Large silicon-carbide (SiC) mirrors (1.7 0.7 m2)
Ultra-stable large size SiC structures for payload optical bench
Large deployable solar array/sunshield assembly
Phased-array antenna for high data rate (1 Mbps) in far orbit (L2)
Data processing, object classification and physical parametrization Technology developments and challenges
Organisation of scientific work : Organisation of scientific work
Working groups: about 150 European ‘core’ and ‘associate’ members
GAIA Science Team (GST) : GAIA Science Team (GST) Frederic Arenou (Meudon)
Coryn Bailer-Jones (MPIA, Heidelberg)
Ulrich Bastian (ARI, Heidelberg)
Erik Hoeg (Copenhagen)
Andrew Holland (Leicester)
Carme Jordi (Barcelona)
David Katz (Meudon)
Maria Lattanzi (Torino)
Lennart Lindegren (Lund)
Xavier Luri (Barcelona)
Francois Mignard (Nice)
Michael Perryman (Project Scientist, ESA)
Current GAIA activities : Current GAIA activities ESA/industrial:
Phased array antenna (Alcatel)
High stability optical bench (Astrium)
Telemetry budget and compression algorithms (ESA)
FEEPs: will be based on SMART-2 activities (ESA + industry)
Proof of concept data reduction system (Barcelona + GMV)
New important industrial study contracts (CCD and focal plane study, mirrors) are on hold due to internal ESA SPC/IPC conflict
Scientific community (working groups):
On-board detection algorithms
Detailed specification of radial velocity instrument
Definition of optimal photometric system
Simulations of data stream
Development of object classification and physical parametrization methods
Data Analysis: Concept and requirements : Data Analysis: Concept and requirements Capacity: ~200 Terabytes (1 Tb = 1000 Gb)
Overall system: centralised global iterative approach
Peculiarity: data mixed-up in time, position and object
Processing requirements: entire task is ~1019 flop
Data base structure: e.g. Objectivity
Results: time-critical results available early (NEO, supernovae etc)
Prototype: Hipparcos global astrometry re-reduced during concept study
Data processing comparison : Data processing comparison
GAIA: 1 Mbps, 200 TB
SDSS: 20TB will be collected; final catalogue ~ 1 TB
Planck: data rate 100kbps, maps ~ 2 Gb
VLT: 80 TB over 6 years
GSC2: 6 TB at end 1999
CERN: LHC (~ Petabytes)
SLAC: BaBar (~1TB/day)
Human Genome Database: ~25 GB
Data processing demonstration (GDAAS) : Data processing demonstration (GDAAS) under development since mid-2000 (GMV/UB/CESCA)
sky divided into hierarchical triangular mesh (level 6)
presently: 8 nodes, 4 processors per node, 0.5 Tbyte disk
telemetry ingestion, object matching, sphere iteration
iterative processing for 1 million stars (final results April 2002)
platform for further development/experimentation
Object classification/physical parametrization : Object classification/physical parametrization classification as star, galaxy, quasar, supernovae, solar system objects etc.
determination of physical parameters:
- Teff, logg, [Fe/H], [/H], A(), Vrot, Vrad, activity etc.
combination with parallax to determine stellar:
- luminosity, radius, (mass, age)
use all available data (photometric, spectroscopic, astrometric)
must be able to cope with:
- unresolved binaries (help from astrometry)
- photometric variability (can exploit, e.g. Cepheids, RR Lyrae)
- missing and censored data (unbiased: not a ‘pre-cleaned’ data set)
multidimensional iterative methods:
- cluster analysis, k-nn, neural networks, interpolation methods
required for astrometric reduction (identification of quasars, variables etc.) produce detailed classification catalogue of all 109 objects
Top level classification system : Top level classification system
Recent developments : Recent developments Nov. 2001: Ministerial meeting reduces science budget
by 435 MEuro over 2002-2006 (20% reduction) Nov. 2001: ESA+Astrium start to identify cost savings Oct. 2000: GAIA approved by SPC for launch by 2012 Dec. 2001: SPC requests review of whole ESA science program April 2002: Astrium presents revised GAIA design to GST May 2002: ESA/Astrium deliver final report to SPC June 2002: SPC decide on future science program April 2002: AWG subgroup (Rix, Aerts, Ward) reports on GAIA
to AWG; (AWG to SSAC to SPC)
GAIA cost saving measures (ongoing) : GAIA cost saving measures (ongoing) Substantial savings possible if released from ESA constraints:
re-use of satellite subsystem designs from other missions
cheaper contract competition mechanism
Soyuz-Fregat launch instead of Ariane 5 (110 40 MEuro)
smaller mirrors in along-scan direction, accommodated
by increased across-scan dimension, field-of-view size...
Other possible cost savings from:
smaller solar array/sunshield by reducing solar aspect angle
(accommodate for lost astrometric precision in optics)
C-SiC optical bench
unification of pixel scales
field superposition (as in Hipparcos)
smaller ESA project team
Cost reduction from 570 to 400-450 MEuro possible
without any reduction in accuracies or scientific goals
Main performances and capabilities : Main performances and capabilities Accuracies:
4 as at V=10 10 as at V=15 200 as at V=20
radial velocities to few km/s complete to V=17-18
10 as distances to 1% at 1 kpc or 10% at 10 kpc (V=15)
10 as/yr at 20 kpc 1 km/s
Capabilities:
sky survey in four bands at ~0.1 arcsec spatial resolution to V=20
15 band multi-epoch photometry to V=20
dense quasar link to inertial reference frame
every star observed in the Galaxy and Local Group will be seen to move
GAIA will quantify a 6-D phase space for over 300 million stars
and a 5-D phase-space for over 109 stars
Slide74 : GAIA and our Galaxy 10 as = 10% distances at 10 kpc 10 as/yr = 1 km/sec at 20 kpc
Hyades (animation) : Hyades (animation) Hyades 60,000 years Perryman et al. (1997)
Gravitational light deflection : Gravitational light deflection de Bruijne (2002)
GAIA stands for ... : GAIA stands for ... Global Astrometric Interferometer for Astrophysics Galactic Astrophysics through Imaging and Astrometry General Astrometric Instrument for Astronomy Great Advances In Astrophysics Great Accuracy In Astrometry