Transcript The Cosmic Microwave Background Lecture 1 Elena Pierpaoli Brief History of time (Cosmic Microwave Background)

The Cosmic Microwave
Background
Lecture 1
Elena Pierpaoli
Brief History of time
(Cosmic Microwave Background)
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
•
•
•
•
•
Y ear data receiv ed
Spatial resolution (deg)
Frequencies (GHz)
Polarization
Sensitiv ity (muK/30' pix)
PLANCK:
Smaller beam
Lower noise
Polarization
Better frequency coverage
COBE
1992
7
30-90
no
WMAP
2003
0.23
22-94
y es
10.5 (8y rs)
Planck
2009
0.08
30Ğ857
y es
1.4
Measuring the Fundamental Properties of the
Universe
Radiation
Observables
Matter
SDSS slice
CMB - Cosmic Microwave Background
(Temperature and Polarization)
DT(q,f) = S a
c = S |a |2
l,m
l
m
l,m
Yl,m (q,f)
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 equations
Photons
Cold dark amtter
Baryons
metric
Massive neutrinos
Massless neutrinos
Evolution of fluctuations
Ma & Bertschinger 95
Line of sight approach
Seljak & Zaldarriaga 06
Polarization
Due to parity symmetry of the density field, scalar perturbations
Have 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
on fluctuations
Fluctuation on scale  enters the horizon
Derelativization
Neutrinos free-stream
Neutrinos do not free-stream
(I.e. behave like Cold Dark Matter)
on expansion
heavy
Radiation dominated
Matter dominated
light
Recombination
(T=0.25 eV)
– change the expansion rate
– Change matter-radiation equivalence (but not recombination)
Expan. factor a
2) The relativistic energy density Nn
Nn = (rrad - rg) / r1n
Matter dominated
Radiation dominated
3n
Expan. factor a
>3n
Recombination
• Effects:
CONSTRAINTS:
– change the expansion rate
– Change matter-radiation equivalence (but not the Before WMAP: Nn <17
radiation temperature, I.e. not recombination)
After WMAP:Nn< 6.6
• Model for:
– neutrino asymmetry
– other relativistic particles
– Gravitational wave contribution
(Smith, Pierpaoli, Kamionkowski 2006)
(Pierpaoli MNRAS 2003)
Neutrino species
Bell, Pierpaoli, Sigurdson 06
Neutrino interactions