Recent Results from the Wilkinson Microwave Anisotropy Probe

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Recent Results from the Wilkinson Microwave
Anisotropy Probe

• YKIS 2005
• June 29, 2005
• Eiichiro Komatsu
• (University of Texas at Austin)

WMAP Science Team
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Full Sky Microwave Map
COBE/FIRAS T2.725 K
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COBE/FIRAS, 1990
Perfect blackbody Thermal equilibrium Big Bang
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Temperature Fluctuations

• Radiative transfer in a perturbed universe
• (perturbations are small 10-5)

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COBE/DMR, 1992
Gravity is STRONGER in cold spots DT/TF
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R. Sachs A. Wolfe, 1967

• SOLVE GENERAL RELATIVISTIC BOLTZMANN EQUATIONS TO
  THE FIRST ORDER IN PERTURBATIONS

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Use temperature fluctuations, QDT/T, instead of
f
Expand the Boltzmann equation to the first order
in perturbations
where
describes the Sachs-Wolfe effect purely GR
fluctuations.
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For metric perturbations in the form of
Newtonian potential
Curvature perturbations
the Sachs-Wolfe terms are given by
where g is the directional cosine of photon
propagations.

• The 1st term gravitational redshift
• The 2nd term integrated Sachs-Wolfe effect

h00/2
(higher T)
Dhij/2
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WMAP, 2003

• WHAT DOES WMAP SEE??

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SMALL SCALES
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Hydrodynamic Perturbations
Collision term describing coupling between
photons and baryons via electron scattering.

• When coupling is strong, photons and baryons move
  together and behave as a single fluid.
• When coupling becomes less strong, they behave as
  two components with shear viscosity and heat
  conductivity
• So, the problem can be formulated as
  hydrodynamics. (cf S-W effect was pure GR.)

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Boltzmann to Hydrodynamics

• Multipole expansion
• Energy density, Velocity, Stress

Energy density
Velocity
Stress
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Photon Transport
f2 3/4 FA -h00/2, FH hii/2 tCThomson
scattering optical depth
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Baryon Transport

• Cold Dark Matter

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The Strong Coupling Regime

• SOUND WAVE!

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Wave Form Tells Us Cosmological Parameters
Jungman, Kamionkowski, Kosowsky, Spergel
(1996) Hu Sugiyama (1996)

• Higher baryon density
• Lower sound speed
• Compress more
• Higher peaks at compression phase (even peaks)

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DO WE HEAR THE SOUND?
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How to See the Sound

• The angular power spectrum, Cl
• Cl measures the amplitude of temperature
  fluctuations at a given angular scale.
• Decompose temparature fluctuations into Waves

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Sound Wave on the Sky
Amplitude of temperature fluctuations at a given
scale, lp/q
400
800
200
40
100
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Multipole moment lp/q
Small scales
Large scales
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Weighing Dark Matter
where g is the directional cosine of photon
propagations.

• The 1st term gravitational redshift
• The 2nd term integrated Sachs-Wolfe effect

h00/2
(higher T)
Dhij/2
During the radiation dominated epoch, even CDM
fluctuations cannot grow (the expansion of the
Universe is too fast) thus, dark matter
potential gets shallower and shallower as the
Universe expands --gt potential decay --gt ISW --gt
Boost Cl.
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Weighing Dark Matter

• Smaller dark matter density
• More time for potential to decay
• Higher first peak

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Measuring Geometry
Sound cross. length

• W1

• Wlt1

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Geometry Test Result

• Geometry is Euclidean Flat W Wm WL 1

W1.020.02
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Energy Budget

• Composition of the Universe
• Baryonic Matter Wb 4.70.6 (Wbh20.0240.001)
• Dark Matter Wcdm 247 (Wmh20.140.02)
• Dark Energy WL 717

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Expansion Ratea.k.a. Hubble Constant

• Hubble Constant 725 km/s/Mpc

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Initial Fluctuations

• CMB fluctuations were not created spontaneously
  at the surface of last scatter!
• Rather, the fluctuations were generated in the
  ultra early Universe --- INFLATION
• Inflation predicts initial (or primordial or
  seed) fluctuations with a specific Shape
  P(k)Akn-1
• n is called a tilt, which determines the slope
  of the power spectrum.
• ngt1 BLUE spectrum, having more small scale power
• nlt1 RED spectrum, having more large scale power
• n1 Scale Invariant spectrum, having equal power
  at all scales
• Inflation predicts n1.

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Tilt

• Primordial Tilt n 0.990.04

Cosistent with Inflationary Spectrum
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Polarized CMB Fluctuations

• Test of Standard Model
• First Star Formation
• Primordial Gravity Waves

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• Temperature anisotropy can be generated by
  gravitational effect via the SW term.
• Polarization is generated only through scattering.

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Source of Polarization

• Linear polarization will be generated from
  temperature quadrupole
• Circular polarization will NOT be generated.

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Physics of CMB Pol.

• Temperature quadrupole at the surface of last
  scatter generates polarization.
• Quadrupole is generated by VELOCITY GRADIENT.
  (Tight coupling must be broken)

electron
isotropic
no net polarization
anisotropic
net polarization
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Photon Transport
Quadrupole
f23/4 FA -h00/2, FH hii/2 tCThomson
scattering optical depth
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Primordial Gravity Waves

• Gravity waves create quadrupolar temperature
  anisotropy --gt Polarization
• Directly generate polarization without kV

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E-mode and B-mode
Seljak Zaldarriaga (1997) Kamionkowski,
Kosowsky, Stebbins (1997)

• Polarization is a rank-2 tensor field.
• One can decompose it into a gradient-like
  E-mode and a curl-like B-mode.

E-mode
B-mode
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Power Spectrum
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E-mode Polarization as a Test of the Standard
Model

• Polarization is generated from temperature
  fluctuations, which are already measured very
  precisely.
• Since we know temperature, we can make
  predictions for what we should see in the
  polarization.
• Do we see it or not?
• Parameter-free
• FUNDAMENTAL TEST OF THE STANDARD MODEL!!

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WMAP Polarization Confirms It!
Prediction from the Temperature Data
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The Universe Reionized

• CMB emitted at z1089.
• 15 of CMB was re-scattered in a reionized
  universe.
• The estimated reionization redshift 20, or 200
  million years after the Big-Bang.

IONIZED
z1089, t1
NEUTRAL
First-star formation
z20, t0.17
REIONIZED
z0
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Measuring Optical Depth

• Since polarization is generated by scattering,
  the amplitude is given by the number of
  scattering, or optical depth of Thomson
  scattering
• which is related to the electron column number
  density as

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Polarization from Reioniazation
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B-mode is a Smoking-Gun for Gravity Waves

• Sachs-Wolfe effect and hydrodynamical effects
  mentioned before DO NOT PRODUCE ANY B-MODE BUT
  ONLY E-MODE.
• Detection of the B-mode is a strong evidence for
  the primordial gravity waves from Inflation.

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SUMMARY FROM WMAP

• WMAP has measured the Sound Waves as predicted
  by cosmological linear perturbation theory, BOTH
  IN TEMPERATURE AND POLARIZATION.
• Cosmological parameters determined.
• Evidence for the early star formation.
• Consistency with Inflationary spectrum.
• Next Frontier I -- Hunting B-mode!
• Would WMAP 4yr, , 8yr data and/or Planck data do
  it? Lets cross our fingers
• Next Frontier II -- Better determinations of the
  inflationary spectrum (a value of n) toward the
  inflationary model. ? Is CMB the only way?

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Smithsonian Astrophysical Observatory University
of Texas, Austin Lockheed Martin
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Cosmic Inflation Probe will characterize the
physics underlying inflation by precisely
measuring the power spectrum of matter density
fluctuations in the present-day universe. The
experiment involves a survey of the galaxy
distribution over 140 sq. degrees from z3 to
6.5 using Ha as the tracer. The CIP mission has
an extremely simple instrument design and
mission plan. The team includes SAO, UT, and
Lockheed-Martin who are currently carrying out
a NASA funded study
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Cosmology - Exciting, but Embarrassing Situation

• Successful determinations of the cosmological
  parameters have revealed that we dont understand
  most of the universe!

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How much we dont know about the universe
10-34 sec Inflation Dark Energy I
Log(Time)
lt30,000 yrs Radiation Era Radiation
lt8 billion yrs Matter Era Dark Matter
ltnow Dark Energy Era Dark Energy II
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Four Big Questions in Cosmology

• The nature of dark matter
• What are they? How many of them?
• The nature of dark energy
• What is it?
• Modification to gravity? Another form of energy?
• The origin of baryons
• Physics of Baryogenesis?
• The physics of inflation
• Did it happen at all?
• If so, how did it happen? What powered inflation?

CIP
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Observe Inflation

• Inflation generates primordial fluctuations in
  spacetime.
• (a) Fluctuations inherited in radiation
• Cosmic Microwave Background
• Temperature Anisotropy
• Polarization Anisotropy
• (b) Fluctuations inherited in matter
• Dark Matter Distribution (Gravitational Lensing)
• Galaxy Distribution (Redshift Surveys)
• Gas Distribution (Lyman-alpha clouds)
• (c) Fluctuations in spacetime itself
• Primordial Gravitational Waves

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Inhomogeneous
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Andrei Linde

• The number of papers whose title contains
  inflation (as of today) 121
• New Inflation (1981, cited 1430 times)
• Chaotic Inflation (1983, cited 867 times)
• Hybrid Inflation (1994, cited 433 times)
• Dr. Inflationary Universe

But, which model is right?
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Approaching the Inflationary Paradigm

• 0th order test did inflation happen?
• Is the observable universe flat?
• Are fluctuations Gaussian?
• Are fluctuations nearly scale independent?
• Are fluctuations adiabatic?
• 1st order test which model is right?
• Deviation from Gaussianity?
• Deviation from scale independence?
• Deviation from adiabaticity?

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Did Inflation Happen?

• Flatness (Wtot 1) Wtot 1.02 0.02
• Gaussianity (NL1) -58 lt NL lt 134
• Scale invariance (ns1) ns 0.99 0.04
• Adiabaticity (DT/T(1/3)Dr/r) deviation lt 30

Spergel, Verde, Peiris, Komatsu et al. (2003)
Komatsu et al. (2003)
Spergel, Verde, Peiris, Komatsu et al. (2003)
Peiris, Komatsu et al. (2003)
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Dev. from Scale Invariance

• Different wave-numbers probe different parts of
  potential.
• We need to cover many decades in wave-number to
  determine the shape of potential
• Require a variety of probes.

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The Current State-of-the-Art
V(f)
f
f
f
f
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Toward the Inflation Model

• What is necessary?
• More accurate measurements of P(k)
• Not just statistical error! Minimum systematic
  error
• Sample more k-modes
• One solution A galaxy survey at high-z
• Why high-z? Less non-linear power!

As the universe ages, gravitational effects
distort initial power spectrum on increasingly
larger scales At z6, non-linear contribution
at k1 Mpc-1 is about 15.
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CIP will nail it!
V(f)
f
f
f
f
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MESSAGE FROM CIP

• CIP will measure the inflationary parameters down
  to
• Tilt - 0.0017
• Running - 0.0020
• As a bonus, it will lift massive degeneracies
  between these parameters and the other
  inflationary parameters constrained by CMB
• Gravity wave amplitude
• Deviation from adiabatic fluctuations
• Hopefully, CIP, in combination with CMB
  experiments, will nail the inflationary model.