The Cosmic Microwave Background and the WMAP satellite results

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The Cosmic Microwave Background and the WMAP
satellite results

• Elena Pierpaoli (Caltech)

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Outline

• What is the Cosmic Microwave Background (CMB)
  radiation and why it is important
• Properties frequency spectrum, temperature,
  (an)isotropy
• The satellite missions COBE, WMAP and Planck
• The sky map and the power spectrum
• Where we stand now the WMAP results
• Perspectives Planck predictions

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Recombination
Reionization
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Penzias and Wilson discovered the 3 K CMB
radiation in 1965 (and received the Nobel Prize
for it in 1978)
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The space experiments
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Properties the frequency spectrum
The CMB radiation is a black body with
temperature T2.726
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Properties isotropy and anisotropies

• The CMB radiation is isotropic
• We are moving with respect to the CMB rest frame
• There are tiny anisotropies, imprints of
  matter-radiation fluctuations.

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The CMB anisotropies map
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The power spectrum
DT(q,f) S al,m Yl,m (q,f) cl Sm al,m2
The power spectrum is the most compact way to
describe (all) the cosmological information in a
sky map. It allows efficient comparison between
theory and observation.
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Measuring the power spectrum
Pierpaoli, Scott, White (Science, 2000)
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The cosmological parameters

• Hubble constant H0 (v H0 d)
• Curvature Wk?? Cl
• densities
• matter density Wm rm /rcrit
• baryon density Wb Cl
• dark matter density Wdm rdm /rcrit Cl
• reionization/optical depth t Cl
• nature of dark matter (Cold, warm or hot?) and
  dark energy
• nature of primordial density perturbations (e.g.
  primordial spectral index ns)

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The cosmological parameters from WMAP
2) Precise history of the Universe
1) The Universe is flat
tUniverse 13.7 Gyr ( 0.2) trecomb380 Kyr (
10) treionization 200 Myr
3) Fluctuations are Gaussian (confirmation for
inflation)
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Perspectivesthe Planck satellite

• Higher beam
• Lower noise
• Polarization
• Better frequency coverage

Wm within 0.5 per cent H0 within 0.4 per
cent Wb within 0.5 per cent
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Summary

• The Cosmic Microwave Background is the relic
  radiation of the Big Bang
• By studying the anisotropies of the CMB it is
  possible to determine the main cosmological
  parameter with the precision of a few percent
• Future satellite missions (Planck) will improve
  these constraints by one order of magnitude

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The Suniaev-Zeldovich clusters
Frequencies of observation
vc
- Thermal and kinetic signal expected - Signal is
independent of redshift - Signal scales as ne -
Need complementary information on redshift from
other data. - Future surveys SPT, ACT (high
resolution), Planck (all sky)