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The Cosmic Microwave Background. Lecture 1 Elena Pierpaoli . (Cosmic Microwave Background). Brief History of time. Properties: isotropy and anisotropies. The CMB radiation is isotropic We are moving with respect to the CMB rest frame - PowerPoint PPT Presentation
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The Cosmic Microwave Background
Lecture 1Elena Pierpaoli
(Cosmic Microwave Background)
Brief History of time
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.
Space Missions
• PLANCK:• Smaller beam• Lower noise• Polarization • Better frequency coverage
COBE WMAP PlanckYear data received 1992 2003 2009Spatial resolution (deg) 7 0.23 0.08Frequencies (GHz) 30-90 22-94 30–857Polarization no yes yesSensitivity (muK/30' pix) 10.5 (8yrs) 1.4
SDSS sliceMatterRadiation
CMB - Cosmic Microwave Background(Temperature and Polarization)
Observables
Measuring the Fundamental Properties of the Universe
DT(q,f) = S al,m Yl,m (q,f) cl = Sm |al,m|2
d (x) = dr/r (x) d (k) = FT[d (x)] P(k) = < |d (k)|2> Pgal(k) = b2 P(k)
bias
The power spectrum
Nolta et al 08
The decomposition of the CMB spectrum
Challinor 04
Evolution equationsPhotons
Massive neutrinosMassless neutrinos
Cold dark amtter
Baryons
metric
Evolution of fluctuations
Ma & Bertschinger 95
Line of sight approach
Seljak & Zaldarriaga 06
Polarization
Due to parity symmetry of the density field, scalar perturbationsHave U=0, and hence only produce E modes.
Scattering and polarization
If there is no U mode to start with, scattering does not generate it. No B mode is generated.
Scattering sources polarization through the quadrupole.
Tensor modes
Parity and rotation symmetry are no longer satisfied. B modes could be generated, along with T and E.
The tensor modes expansion
Scattering only produces E modes, B Are produced through coupling with E And free streaming.
Power spectra for scalar and tensor perturbations
Tensor to scalar ratio r=1
Effect of parameters
• Effect of various parameters on the T and P spectrum
1)Neutrino mass: Physical effects
Fluctuation on scale enters the horizon
Neutrinos free-stream Neutrinos do not free-stream(I.e. behave like Cold Dark Matter)
Derelativization
on fluctuations
on expansion Expan. factor a
Recombination
Radiation dominated Matter dominatedheavy
light
(T=0.25 eV) – change the expansion rate – Change matter-radiation equivalence (but not recombination)
2) The relativistic energy density Nn
Nn = (rrad - rg) / r1n
• Effects: – change the expansion rate– Change matter-radiation equivalence (but not the
radiation temperature, I.e. not recombination)• Model for:
– neutrino asymmetry– other relativistic particles– Gravitational wave contribution (Smith, Pierpaoli, Kamionkowski 2006)
Expan. factor a
Recombination
Radiation dominated Matter dominated3n
>3n
CONSTRAINTS:
Before WMAP: Nn <17
After WMAP:Nn< 6.6
(Pierpaoli MNRAS 2003)
Neutrino species
Bell, Pierpaoli, Sigurdson 06
Neutrino interactions