First Year Wilkinson Microwave Anisotropy Probe WMAP Results

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First Year Wilkinson Microwave Anisotropy Probe
(WMAP) Results

• Hu Jian
• THCA
• Mar 6, 2003

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Outline

• About WMAP
• What is CMB power spectrum
• WMAPs cosmological results
• CMB polarization and reionization
• Perspects
• http//map.gsfc.nasa.gov/

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• The WMAP Spacecraft was launched on June 30,
  2001. It was an almost perfect launch, on time to
  the second. This photo is taken at Kennedy
  Spaceflight Center Launch, Pad 17B.

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WMAP Leaving the Earth/Moon Orbit, headed toward
L2WMAP used the Moon to gain velocity for a
slingshot to L2. After 3 phasing loops around the
Earth, WMAP flew just behind the orbit of the
Moon 3 weeks after launch. Using the Moon's
gravity, WMAP steals an infinitesimal amount of
the Moon's energy to maneuver into the L2
Lagrange point, one million miles (1.5 million
km) beyond the Earth.
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Diagram of the Lagrange Point gravitational
forces associated with the Sun-Earth system. WMAP
orbits around L2, which is about 1.5 million km
from the Earth. The forces at L2 tend to keep
WMAP aligned on the Sun-Earth axis, but requires
course correction to keep the spacecraft from
moving toward or away from the Earth.
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WMAP Spacecraft Diagram
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COBE Spacecraft, NASA. Artist's ConceptionThe
COBE spacecraft is the predecessor to the WMAP
Project. COBE was launched into an Earth Orbit in
1989 to make a full sky map of the microwave
radiation leftover from the Big Bang. The first
results were released in 1992.
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Cosmic HistoryWMAP observers the first light to
break free in the infant Universe, the afterglow
of the Big Bang. This light emerged 380,000 years
after the Big Bang. Patterns imprinted on this
light reflect the conditions set in motion a tiny
fraction of a second after the Big Bang. In turn,
the patterns are the seeds of the development of
the structures of galaxies we now see billions of
years after the Big Bang.
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• Temperature field
• Monopole T2.7250.002K

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• Dipole the motion of the solar system relative
  to CMB
• in the direction (l, b) (263º.850º.1,
  48º.250º.04).
• ?T3.3460.017mK

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• COBE Map
• subtract monopole, dipole and our Galaxy
• ?T/T 10-5

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The Microwave Sky The WMAPs first all-sky
picture of the infant universe.
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• WMAP
• Full sky survey with angular resolution 0.2o
• 5 frequencies (GHz)
• K 22.8, Ka 33.0, Q 40.7, V 60.8, W 93.5
• 45 times the sensitivity of the COBE
• 33 times the angular resolution of COBE

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• WMAP

Ka
K
Q
W
V
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What is CMB power spectrum?
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• CMB spectrum before WMAP

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• CMB Power Spectrum from WMAP

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Content of the Universe

• The new constraints on the dark energy seems
  more like a "cosmological constant" than a
  negative-pressure energy field called
  "quintessence". But quintessence is not ruled
  out.
• Fast moving neutrinos do not play any major role
  in the evolution of structure in the universe.
  They would have prevented the early clumping of
  gas in the universe, delaying the emergence of
  the first stars, in conflict with the new WMAP
  data.

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The new value of H0

• WMAPs measurement km s-1Mpc-1
• HST Key Project value of H07237 km s-1Mpc-1
• (by SN Ia)
• The result is consistent with the measurements
• Gravatational lensing
• Sunyaev-Zeldovich effect

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The age of the Universe

• The first acoustic peak in the CMB power spectrum
  represents a known acoustic size (rs 1472 Mpc)
  at a known redshift (zdec 10891). From these,
  WMAP measures the age of the universe (t0
  13.70.2 Gyr) to an accuracy of 1 by determining
  the CMB light travel time over the distance
  determined by the decoupling surface (dA
  14.00.2-0.3 Gpc) and the geometry of the
  universe (i.e., flat).
• The age of the universe is also estimated via
  stars in three ways
• the main sequence turn-off in globular clusters
  yielding a cluster age of 121 Gyr (Reid 1997)
• the temperature of the coldest white dwarfs in
  globular clusters yielding a cluster age of
  12.70.7 Gyr (Hansen et al. 2002)
• nucleosynthesis age dating yielding an age of
  15.64.6 Gyr (Cowan et al. 1999).

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Matter Density

• The matter density affects the height and shape
  of the acoustic peaks. WMAP measures the matter
  density
• Om0.270.04
• From the galaxy data, Verde et al. (2002) find
  Om0.270.06
• WMAP measures the bayron-to-matter ratio
• ObOm-10.170.01
• The combined X-ray and SZ measurements give a
  value of ObOm-10.1140.014

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Frame one depicts temperature fluctuations in
the oldest light in the universe which correspond
to slight clumping of material in the infant
Universe.
Frame two shows matter condensing as gravity
pulls matter from regions of lower density to
regions of higher density.
Frame three captures the era of the first stars,
200 million years after the Big Bang. Gas has
condensed and heated up to temperatures high
enough to initiate nuclear fusion, the engine of
the stars.
Frame four shows more stars turning on. Galaxies
form along those filaments first seen in frame
two, a web of structure.
Frame five depicts the modern era, billions upon
billions of stars and galaxies... all from the
seeds planted in the infant Universe.
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CMB Polarization physical origin Thomson
scattering
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• Cosmological importance of CMB polarization
• structure formation from primordial fluctuations
• the existence of polarization is
  inevitable
• the detection of polarization provides
  important
• check on the structure formation theory
• different sources of fluctuations (scalar,
  vector, tensor) generate different polarization
  patterns
• scalar E-mode dominant
• vector B-mode dominant (defect model)
• tensor E-mode and B-mode are comparable
• distinguish different components in initial
  fluctuations and thus falsify different theories
  and set constraints on theories
• break degeneracy in determining cosmological
  parameters

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• Reionization
• Observations indicate that the universe
  today is mostly ionized. This means that after
  the universe recombined at z 1000, it went
  through a reionization stage. The sources for
  reionization could be first generation of stars,
  quasars etc.

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• The effects on CMB
• Differential optical depth for Thomson
  scattering
• where a scale factor of the universe, ne
  electron density,
• xe ionization fraction, sT Thomson cross
  section
• The total optical depth at conformal time s
• Fraction of photons that directly come from the
  recombination epoch exp(-t)
• Fraction of photons scattered after reionization
  before reaching us 1- exp(-t)
• Then the peak position lpeak 2(s0
  sri)/(sri-sD) 2(zri)1/2
• The height of the peak 1- exp(-tri)
• For WMAP observations
• tri 0.17 0.04 (from TE correlation)
• zri 11 30 (depending on reionization
  models)

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• With same optical depth t, different reionization
• histories leave imprints on the CMB
  polarization,
• and the differences are potentially detectable.
• CMB observations and high redshift quasar
  observations start to enable people to study the
  detailed reionzation history of the universe in
  the redshift range 30gt z gt6
• The early reionization observed by WMAP
  constrains the formation epoch of first
  generation of luminous objects (e.g., Pop III
  stars), which further set constraints on
  cosmological models on structure formation.

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• Before DASI (Degree Angular Scale
  Interferometer),
• there were no definite detections of
  polarization
• DASI observation 140 lt l lt 900
• first time detection of CMB polarization
• The observational results are consistent with
  the theoretical predictions based on that the
  CMB anisotropy is due to primordial scalar
  adiabatic fluctuations,
• and quantitatively agree with that of
  concordance model with
• OB0.05, Ocdm0.35, O?0.60, h0.65

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DASI (in Antarctic)
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CMB polarization detected by DASI
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Planck will be launched in 2007 by ESA
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Plancks CMB map
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• Thanks!