The Universe according to WMAP III

1
The Universe according to WMAP III

• Jan Pieter van der Schaar
• University of Amsterdam

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Outline

• Introduction
• CMB basics
• WMAP mission
• First year data release
• The WMAP III data release
• Main new features and results
• Third year spectra
• Implications for Cosmology
• Cosmological parameters
• Consistency with other data
• Conclusions

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Too much anticipation?

• December 2004 email exchange

There are rumours that the wiggles in the
spectrum are confirmed in the new Wmap release so
it may really be interesting
"...wiggles in the spectrum have been
confirmed..." ??? I have not heard these rumors.
Have any of you? Is it true?
there are several rumours about the new WMAP
data (you know, they are delaying so much the
release that everybody thinks there must be
unexpected things) but I also heard
independently from two persons, who heard it from
people involved in Wmap, that the wiggles in the
spectrum are confirmed, within the errors (which
are anyway very small already)

• Final release date March 16 2006!

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CMB basics

• Photon afterglow after decoupling
• Last scattering surface z 1100
• Perfect black body T2.725 K
• Homogeneous and isotropic universe
• Structure formation predicts small CMB
  temperature anisotropies
• First detected by COBE at 10-5 level (1992)
• Precision probe of many, almost all, cosmological
  parameters
• Subsequently ACBAR, BOOMERanG, MAXIMA, CBI, ,
  WMAP

Inflation solves horizon, flatness, defect
problem Beautiful mechanism for the generation of
a scale invariant, adiabatic, Gaussian spectrum
of super-horizon scalar tensor perturbations
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CMB anisotropies

• Tightly coupled baryon-photon fluid
• Pressure vs gravity (within sound horizon)
• Forced damped oscillator equation
• Produces acoustic peaks
• After decoupling free streaming from last
  scattering surface
• Large scale primordial modes (low l) hardly
  affected (Sachs-Wolfe plateau)
• Gaussian distribution for every l
• Cosmic variance 2l1 samples

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Polarization

• Quadrupole anisotropy E-mode
• Cross-correlated spectrum ltTEgt
• Super-horizon adiabatic perturbations
• Probe of optical depth (reionization)
• Removes certain degeneracies
• Tensor perturbations EB-mode
• E-mode gradient of potential
• B-mode curl of potential

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WMAP mission

• Launched in 2001
• L2 orbit
• Full sky observations in 6 month period
• In operation until 2008

WMAP team, C.L. Bennett (PI) NASA and
Princeton University. Around 27 people,
including UCLA, U. Chicago, UBC, Toronto and
Brown.
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First year data release

• Februari 2003 very impressive results!
• Consistent with other data
• Small scale CMB measurements
• Large scale structure (SDDS,2dFGRS)
• Supernovae type IA measurements
• Room for improvement
• Foregrounds (particularly for polarization)
• Data analysis, integration
• 1 breakthrough of the year 2003 SCIENCE

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Some surprises

• Large optical depth
• Early reionization (stars)
• Low l anomalies
• Running spectral index?

• Position and height of peaks
• Curvature (flat!)
• Baryon density
• Matter density
• Important degeneracy
• Optical depth and spectral index

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WMAP 3rd year release

• More integration time, better (foreground)
  analysis
• Smaller errors at high multipoles
• Better determination of 3rd peak
• Now includes E-E polarization spectrum
• Better determination of optical depth
• Breaking optical depth/spectral index degeneracy
• Important results
• Optical depth decreased, later reionization
• Spectral index lt 1 !
• Dark Energy equation of state w -1
• Octupole (l3) anomaly gone
• More accurate and shift in matter density
• Running spectral index no longer significant
• Still in excellent agreement with ?CDM flat
  universe, made of baryons, cold dark matter and
  dark energy
• Excellent agreement with other data

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Third year spectra

• Reduced errors, third peak
• Octupole (l3)
• Reionization
• E-E spectrum

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Cosmological parameters

• Parameter estimation
• Best fit 6 parameter ?CDM
• Bayesian statistics, uniform priors
• Markov Monte Carlo chains exploring likelihood
  surface
• Mean vs maximum likelihood

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Departures from best fit

• No urgent reason to add more parameters

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Combined constraints

• Bottomline consistent numbers

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Inflationary parameters

• Some models constrained, but still lots of room
• Constraints on tensor-scalar ratio

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Dark Energy and Neutrinos

• Flat universe, WMAP SNLS w-0.97(0.07, -0.09)
• True cosmological constant?

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Other features

• No sign of non-gaussiannities
• No sign of modulations due to initial state
  modifications (wiggles, potentially probing the
  string scale)

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The Future

• Holy grail B-mode polarization
• Tensor perturbations scale of inflation
• Testing inflation
• Non-gaussiannities
• Surprising features (string theory?)
• ESA Planck satellite (not optimized for
  polarization), expected to launch in 2008
• Ground-based/balloon missions
• USA CMBPOL (before 2020)
• Galaxy surveys, gravitational lensing, 21 cm
  radiation

D. Spergel ultimately one might reach 10-6 level
precision
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Conclusions

• Unprecedented data
• Rigorous test of Standard Model of Cosmology
• Closing in on a cosmological constant
• First hint of departure from scale invariance, as
  predicted by inflation
• What about low multipole (l2) anomaly?
• Axis of evil ?

20
WMAP three-year papers Three-Year Wilkinson
Microwave Anisotropy Probe (WMAP) Observations
Beam Profiles, Data Processing, Radiometer
Characterization and Systematic Error LimitsN.
Jarosik, et.al., submitted Three-Year Wilkinson
Microwave Anisotropy Probe (WMAP) Observations
Temperature ResultsG. Hinshaw, et.al.,
submitted Three-Year Wilkinson Microwave
Anisotropy Probe (WMAP) Observations
Polarization AnalysisL. Page, et.al.,
submitted Three-Year Wilkinson Microwave
Anisotropy Probe (WMAP) Observations
Implications for CosmologyD.N. Spergel, et.al.,
submitted, astro-ph/0302209 Three-Year Wilkinson
Microwave Anisotropy Probe (WMAP) Observations
Three Year Explanatory SupplementM. Limon,
et.al.,
The WMAP Science Team is acknowledged for
providing most of the figures