The Cosmic Microwave Background and the WMAP satellite results Elena Pierpaoli (Caltech) siamo tanto belli e bravi

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

Recombination Reionization

Penzias and Wilson discovered the ~3 K CMB radiation in 1965 (and received the Nobel Prize for it in 1978)

The space experiments:

Properties: the frequency spectrum The CMB radiation is a black body with temperature T=2.726

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.

The CMB anisotropies map

The power spectrum DT(q,f) = S al,m Yl,m (q,f) cl = Sm |al,m|2 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.

Measuring the power spectrum Pierpaoli, Scott, White (Science, 2000) The 1 yr WMAP power spectrum

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)

The cosmological parameters from WMAP 2) Precise history of the Universe 1) The Universe is flat tUniverse= 13.7 Gyr (+ 0.2) trecomb=380 Kyr (+ 10) treionization= 200 Myr 3) Fluctuations are Gaussian (confirmation for inflation)

Perspectives:the 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

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

The Suniaev-Zeldovich clusters Frequencies of observation e- g cluster 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)