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• Thermal History of the Universe and the standard Big-Bang model• The CMB• its origin• a tool for Cosmology• past and forthcoming observations
What can we learn from CMBin the Planck area?
(Planck is going to be launch May 6) Yannick Giraud-Héraud (APC – Paris)
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• General Relativity (Einstein 1915 ; Friedmann 1922 ; Lemaître 1927)
April 21, 2009
Expansion
CMB BBNmatter dark energy curvature
The Big Bang Model
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GUT?
Thermal History of the Universe and the CMB
1. inflation (1/2)
Brief period of exponential expansion(factor 1026 in ~ 10-34 s)
1) Resolve flatness, horizon, relic …problems
2) Perturbation generation- density (scalar) dm ~ EI
6/V’ ~ 10-5
- gravitational (tensor) dog ~ (EI/MPlanck)4
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Thermal History of the Universe and the CMB
1. inflation (2/2)Slow roll potential, in favour today, are caracterized by 2 parameters
€
ε =M p
2
16πV 'V ⎛ ⎝ ⎜
⎞ ⎠ ⎟2
€
η =M p
2
8πV"V
They are related to spectral index of the density fluctuations
€
ns −1 = d lnPs(k)d lnk
€
nT = −2ε
€
ns −1 = −6ε + 2η€
nT = d lnPT (k)d ln(k)
€
r = PT (k)Ps(k)
V1/4~3.3x1016r1/4 GeV
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2. nucleosynthethis
3. thermalization
Thermal History of the Universe and the CMB
LHC conference - IsfahanLarge-scale structure
2dF
theory4. temperature anisotropies
Thermal History of the Universe and the CMB
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5. Energy Contents of the UniverseWhat the Universe is made of?For each component the density is defined in terms of the critical density:
Wcomposante = rcomposante/ rcritical
rcritical ~ 5. GeV/m3
Thermal History of the Universe and the CMB
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6. Geometry of the Universe
flat
closed
openclosed flat open
Size of the horizonat tdec
~100 Mpc
Thermal History of the Universe and the CMB
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7. Shape of the Power Spectrum (1/3)
• Primordial Universe is dominated by radiation no matter collapse
• Baryon starts to collapse at matter-radiation equality
• Acoustic waves induced by radiation pressure propagate at the speed of sound
• Oscillations are frozen at the moment of decoupling
Thermal History of the Universe and the CMB
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Angular power spectrum
Statistically isotropic sky
W = 0,9 ; Wm = 0,15W = 1 ; Wm = 0,25W = 1,1 ; Wm = 0,35
l
l(l+1)/(2T C
MB2 )C
l
Spherical Harmonics Expansion(equivalent to Fourier transform)
l 1/q : l=200 q=1 deg.
Thermal History of the Universe and the CMB7. Shape of the Power Spectrum (2/3)
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Thermal History of the Universe and the CMB7. Shape of the Power Spectrum (3/3)
maps power spectrum• Angular power spectrum
– ~number of fluctuations in respect to their size
• Cℓ– ℓ is inversely proportional
to the angular size ℓ=200 corresponds to q~1o
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8. CMB polarisation anisotropiesLinear polarisation is due to Thomson
scattering (Rees, 1968).
The polarisation of the CMB should be small as it is
Produced by temperature anisotropies
Thermal History of the Universe and the CMB
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• E modes – even parity :
• B modes – odd parity :
- E modes are produced by quadrupolar sources (density fluctuations and gravitational waves)- B modes are produced by gravitational waves and lensing of E
modes
pure E pure BWayne Hu
Thermal History of the Universe and the CMB8. CMB polarisation: decomposition in 2 modes E and B
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( )17.0=τ
1.0=r
41055.6 −×=r
GeVEI16102~ ×
GeVEI15107.5~ ×
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r ≡ T 2
S2 ∝E I
M pl
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
4
- probe of the structure of the Universe- primordial gravitational waves: smoking gun probe of inflation
Thermal History of the Universe and the CMB8. CMB polarisation: power spectra
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Key dates of the CMB observations
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1) discovered at 7.35 cm (4 GHz) (Penzias & Wilson, 1964)
€
T = 2.725 ± 0.002K
highly uniform
510−≈ΔTT
2) dipole ΔT= 3 mK(Smoot et al. 1976)
skmv /600≈(Mather et al. 1999 - COBE)
CMB detection history
3) Perfect black body (COBE Mather et al., 1999) 4) Anisotropies at 7o
(COBE Smoot et al. 1992)
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Balloon experiments (2000-2002): Boomerang, Maxima, Archeops
17
primary
secondary
pivot
horns
bolometers
cryostat
Archeops (2002)
from COBE scale to first acoustic peak
CMB detection history
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WMAP – NASA satellite (launch 2001)
• 2 back to back telescopes• Radiometers cooled
down at 90 K• Bands at 23, 33, 41, 61 et
94 GHz• Angular resolution 13-
52’• Sensitive to polarisation• Rotation 7.57 mHz
CMB detection history
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WMAP/ACBAR power spectrum
Cosmological parameters estimation (WMAP+Acbar+CBI+Large Scale Structure Observations)
€
Wo =1,020,020,02
€
WΛ =0,73−0,04+0,04
€
Wbh2 = 0,023−0,001+0,001
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h = 0,74−0,03+0,03
ns = 0.948+-0.25t = 0.091+-0.009
R<0.2
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Planck: an ESA satellite CMB anisotropies measurements
(temperature and polarization)
International collaboration: European Community (Germany, Denmark, Spain, Finland, France, Italy, Irland, Netherland, UK, Sweden), Canada, Norvege, Switzerland, USA
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Plancklaunch scheduled May 6
Herschel
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Planck is going to orbit around the 2nd
Lagrangian point of the Sun-Earth-Moon system
• the sky will be scanned in 6 months• the mission is expected to last 30 months
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Low Frequency Instrument (LFI) Frequencies: 30 - 70 GHz Wavelengths: 1cm - 5 mm radio detectors (22) Temperature: 20 K (Front-end), 300 K
(Back-end) Angular resolution: 12' (70 GHz) à 33'
(30 GHz) Sensitivity @30 GHz: ~5.4 mK; @70
GHz: 12.7 mK PI: N. Mandolesi (CNR –
Bologna/Italy) IS: M. Bersanelli (U. Milano/Italy)
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High Frequency Instrument (HFI)
Frequencies: 100 - 860 GHz Wavelenghts: 3mm à 400µm Detectors: 52 bolometers Temperature: 0.1 K Angular resolution: 5' (850 GHz) à 9.2' (100 GHz) Sensitivity @100 GHz: ~ 5mK PI: J.L. Puget (IAS - Orsay) IS: J.M. Lamarre (LERMA – Paris)
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Thermal Architecture of Planck HFI
4K
1.6K
0.1K18K
Bolomètres
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Bolometers “Spider web”(Caltech/JPL)
121 Bolometers on a Wafer
857 GHz BolometerNTD Germanium
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Frequency Observations
• Large bandwith coverage : 9 bands
This will allow to subtract foregrounds to the CMB
• Polarization measurement
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High Angular Resolution (5’ for Planck and 7o for COBE)
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High precision temperature measurement
COBE Planck
PlanckWMAP (8 ans)
~ 20 x WMAP sensitivity
Planck will have:
~ 3 x angular resolution
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Main Planck Scientific Goals• for temperature measurements : definitive measurements up to
l=2000 only limited by photon noise of the CMB (astrophysical foregrounds become the major source of uncertainty)• CMB polarization measurements will be the challenging part of
Planck for E mode up to l=1000
Impact on the knowledge of the Big Bang model and on
Fundamental Physics• cosmological parameters at the % level• first constraints on inflation• Study of the large scale structure will be adressed through :• Sunyaev-Zeldovitch survey : 10000 clusters as good tracers of
the dynamics of the Universe
• B polarization measurement• study of the Milky Way• limit on neutrino mass
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Planck simulated maps
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Temperature Power Spectrum
l l
• Power spectrum measurement up the 8th acoustic peak
• Just cosmic variance limited up to l ~2500
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Polarisation Power Spectra
Cross-spectrum TE (t=0.17)
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EE spectrum (t=0.17)Adding EE power spectrum to TT power spectrum will help to reduce the degeneracy to determine the cosmological parameters
Polarisation Power Spectra
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Cosmological Parameters
Planck
WMAP
• Improvment of the knowledge of the cosmological parameters
Ex: Ωb précision 10 times better than with WMAP.
• Degeneracies will be reduced (polarisation)Ex: discrimination between adiabatic and isocurvature perturbations
PLANCK
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Dark Energy Equation of State
Dark energy, responsable of the acceleration of the expansion of the Universe, has an equation of state: p = w r
For a pure cosmological constant: w = -1
Planck will contribute to the measurement of w together with other probes (SNIa, Large Scale Structure, Baryonic Acoustic Oscillation, weak lensing, …),
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Reionisation of the Universe• After a period where the Universe was neutral, a phase
of reionisation occured when the first objects (stars?) have been created
• Signature at large angular scales: pic dans le spectre EE (WMAP)WMAP+ACBAR+LSS Optical depth t = 0,091+-0.008
• Planck will be able to discrimate between different models of the first object formation
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WMAP/Planck capacity measurement of ns
ns = 1 for the red solid line
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WMAP/Planck capacity measurement of ns
ns = 0.95 and no running for the red solid line
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Constraints on tensor modes with Planck
B polarization measurements at low l will put constraints on r
r=0.05 could be detected by Planck and upper limit r<0.03 (95% CL) could be set
simulation with r=0.1 and t=0,17
Efstathiou, Gratton astroph:0903.0345(Planck 24 month survey)
simulation with r=0.1 and t=0,17
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Non-gaussianity properties of the anisotropies
• Inflation models predict nearly perfect model dependant Gaussian fluctuations
• Detection of non-gaussianity will be crucial to discriminate between these models
• Methods: kurtosis, skewness, 3 point statistics, test of isotropy …
WMAP data
Very cold region
Secondary anisotropies: gravitational lensing of the CMB
During their trip, CMB photons are gravitationaly slightly deviated by structures of the Universe
• Coherent deviation of the polarisation at large scale: B mode polarisation at small scale (leak from E mode to B mode) Non-gaussian signatures should be detected by Planck
• Neutrino mass affects structure formation Upper limit on mn: 0.15 eV
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And a lot of other studies will be performed by astrophysicists …
Clusters of galaxies: 30 000 clusters will be detected by Planck using Sunyaev-Zel’dovitch effect (interaction of CMB photons with hot electron gaz in the core of the galaxy clusters)
Extragalactic sources (first survey since FIRAS 1992 with l>100mm)
Study of the Milky Way: dust, free-free,synchrotron radiation magnetic field