Euclid
An ESA mission to map
the Dark Universe
Andy Taylor
Institute for Astronomy, Edinburgh
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ESA Cosmic Vision proposal
imaging & photometric survey
spectroscopic survey
Euclid
All sky imaging, photometric & spectroscopic survey
ESA M-class mission in assessment phase
600Meuro = 450Meuro (ESA)+150Meuro(agencies)
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Euclid Goals
Science Case:
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•
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Dark Energy
Dark Gravity
Dark Matter
Initial Conditions
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Dark Energy
Dark Energy characterized by an Equation of State: P = wρ c
75% of energy budget.
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w = -1/3 (string/curvature)
w = -1 Λ
Scale factor, a
w = 0 (CDM)
a∝t
2 / 3(1+ w )
t
If w = -1 energy-density is Einstein’s
Cosmological Constant, Λ.
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Dark Energy/Dark Gravity
• Big Questions:
• Is Dark Energy Λ?
– Fine-tuning problem: ρV ≈ 10
– Coincidence problem: ρV ≈ ρ m
−120
m
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pl
• Parameterize by
PV = [ w0 + wa (1 − a )]ρV
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Dark Energy: w0-wa constraints
SN+CMB
Euclid:
Lensing
BAO
(Open models)
Evolution of w:
z
w( z ) = w0 + wa
1+ z
CMB
Planck
Flat (k=0)
models
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• Primary probes
– Weak Lensing (WL)
– Baryonic oscillations (BAO)
Massey et al. Nature 445 (2007)
Euclid Cosmological probes
– Galaxy clustering
– Redshift space distorsions
– Cluster counts
– Int. Sachs-Wolfe (cc CMB)
Euclid collaboration 2008
• Secondary probes
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Weak Lensing
• Shape of background galaxies distorted by foreground DM
• Cosmic shear is ~ 1%. Must be measured to high accuracy
Background sources
Dark matter halos
Observer
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Weak Lensing
• Space:
space
– small and stable PSF
⇒ larger number of resolved galaxies
⇒ reduced systematics
ground
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+ Distances (Redshifts): 3D WL
• Distances for 109 galaxies from redshifted colours.
− optical colours possible with ground-based survey (e.g. PS1+2).
• Need Infra-Red (IR) colours from space for high accuracy.
OPTICAL + IR
OPTICAL
zphoto
zphoto
ztrue
ztrue
Abdalla et al 2007
(UCL)
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Baryonic Acoustic Oscillations
• Signature of acoustic
oscillations seen in CMB
• Typical size 150Mpc now
• Need large volume
Space:
– Large sky coverage
– Access to IR Æ deeper
⇒ larger number of galaxies
⇒ 3D spectroscopic
information
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Euclid Cosmological goals
• Measure Equation of state with
~1% on w0 and ~10% on wa.
• Nature of Dark Matter
• Initial conditions (Inflation)
• Test of General Relativity
• Evolution of galaxies
• Clusters physics
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Dark Matter
• 3-D mass mapping:
– Goal: All-sky, high-resolution maps & fly-through.
• WDM:
– X-sections & mass.
• Neutrino’s:
– mν, Nν, ∆mν
• CDM:
– Substructure – high resolution
– Particle Physics constraints: axions, neutralino’s?
• Intrinsic Alignments:
– Halo model, simulations
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Initial Conditions
• Inflationary Perturbation Parameters:
–
–
–
–
–
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As Scalar perturbation amplitude
ns Scalar spectral index
α Scalar spectral index running
r Tensor-to-Scalar ratio
fNL Non-Gaussianity
AISO Isocurvature perturbation modes
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Combination of Probes
• WL
• BAO:
• P(k):
• z-distortions:
• ISW:
• Clusters:
+ CMB
• Covariances between Probes?
• Consistency tests?
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Euclid: all sky survey
Wide Extragalactic
20,000 deg2
Galactic Plane
Deep
~50 deg2
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Legacy
• Visible/NIR imaging survey:
– Morphologies and colors for billions of galaxies out to z~2,
3D Dark Matter maps
• Spectroscopic survey:
– 3D maps of the luminous matter distribution, spectra of 200
million galaxies out to z~2
• Deep survey:
– Infrared imaging to H(AB)=26 and spectroscopy to H(AB)=24:
galaxies 2<z<7, Objects 7<z<10 color selected from YJH
(Impossible from ground)
• Galactic survey:
– Milky way
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Mission & Payload
• Soyuz launcher from
Kourou (French Guiana).
• L2 orbit
• 5 year mission
• Telescope 3 mirrors with
1.2m primary
• Data rate Max 700Gb/day
(compressed)
• Stop and stare.
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3 Instruments
Visible Imaging channel: Æ galaxy shapes
• 36 CCD detectors
– AOCS (4 ccd)
– 0.5 deg2
– 0.10’’ pixels, 0.21’’ PSF FWHM
– 4096 red pixels / CCD
• broad band R+I+Z (0.55-0.92µm)
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3 Instruments
NIR Photometry channel: Æ photo-z’s
• HgCdTe detectors
• 16 arrays
– 0.5 deg2
– 0.3’’ pixels ~ PSF
– 2048x2048 pix / array
• 3 bands Y,J,H (1.0-1.7µm)
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3 Instruments
NIR Spectro channel: Æ redshifts of 1/3 of galaxies
• Slitless spectroscopy
• Investigating:
Digital Micro-mirror Devices
(DMD) based multi-object slit
• 0.5 deg2
• 0.9-1.7µm
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Data Handling Challenges
• Galaxy surveys:
– Need to measure shape of 3 billion galaxies
(see Tom Kitching’s talk).
– Measure spectra of 1 billion galaxies.
• Data flow:
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–
–
–
700Gb/day (compressed)
250Tb/year
1.3 Pb total (c.f Pan-STARRS-1)
Based on Astrowise & PS1 IPP.
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Level 1: Telemetry Euclid
Raw data
House-keeping
Euclid
2A: Raw data processing
Flat fielding
Dark subtraction
CTE correction
Pipeline
Level 2A
2B: Catalogue Production
Aperture Photometry
Astrometry
PSF characterization
Source extraction
Star-galaxy separation
Shape/shear measurement
Photo-z’s
Level 2B
Level S
Simulations
3: Science Analysis
3-D dark matter maps
3-D cosmic shear
Shear ratios
Intrinsic Alignments
Cosmological Parameters
Level 3
Level 4
4: Data Archive/VO
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Data Analysis Challenges
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Peta-Bytes of data to push through pipeline.
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6 layers:
1.
2.
3.
4.
5.
6.
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Data acquisition, book keeping, data compression
Raw Data Reduction
Shape analysis (see Tom Kitchings talk)
Science analysis (map making, power spectra, etc)
Data Archiving
Simulations
How do we simulate large dynamic range?
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And Monte-Carlo surveys ~1000 times?
c.f. CMB temperature & polarisation experiments
(i.e QUaD analysis).
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Simulating Euclid Surveys
• Do we need ensembles of
LCDM Millennium
simulations to test methods,
estimate covariance and
understand systematics?
• Develop Dark Energy/Gravity
simulations.
(Kiessling et al 2009)
• Do we need a Millennium
Simulation at each point in
parameter space?
Simulated all-sky convergence at z =1 (Teyssier et al 2008)
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Simulations Challenge
• How do we get from here to Peta-scale simulations?
• Joint DUEL and Astrosim initiative to explore a
pathway to peta-scale sims for Euclid in Zurich later
this year (ANT, A. Amara, R. Teyssier).
• Engage computing & simulation community and
European theorists to support mission.
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ESA/NASA IDECS Negotiations
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ESA and NASA worried about:
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costs (M-class mission)
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NASA/DOE JDEM (eg Planck vs WMAP).
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6th Jan 2009 start of discussions
April 2009 – discussions on hold.
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Options:
1.
2.
3.
ESA Euclid for WL and BAOs
Joint ESA/NASA/DOE IDECS for WL & BAOs
ESA DUNE WL only and NASA Adept BAO only.
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Summary
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Euclid launch: 2017.
5 year mission
1.4 Pb of data
3 billion galaxies over 3π to z=1
3 Instruments: Vis, NIP, NIS
Methods: WL + BAO (+ secondary and legacy).
• Science goals: Dark energy, dark matter, initial conditions,
modified gravity.
• Computing challenges: data compression, data reduction,
shape analysis, power spectra & parameters, data archiving,
simulations.
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End
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