Transcript z= 1000 - z= 10

Cosmic Microwave
Background Radiation:
z=1000 - z= 10
David Spergel
Princeton University
Standard Cosmological Model

General Relativity + Uniform Universe



Big Bang
Density of universe determines its fate + shape
Universe is flat (total density = critical density)
 Atoms 4%
 Dark Matter 23%
 Dark Energy (cosmological constant?) 72%
Universe has tiny ripples


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Adiabatic, scale invariant, Gaussian Fluctuations
Harrison-Zeldovich-Peebles
Inflationary models
Quick History of the Universe


Universe starts out hot,
dense and filled with
radiation
As the universe expands,
it cools.
• During the first minutes, light
elements form
• After 500,000 years, atoms form
• After 100,000,000 years, stars start
to form
• After 1 Billion years, galaxies and
quasars
Thermal History of Universe
radiation
matter
NEUTRAL
r
IONIZED
103
104
z
Growth of Fluctuations
•Linear theory
•Basic elements have
been understood for
30 years (Peebles,
Sunyaev &
Zeldovich)
•Numerical codes
agree at better than
0.1% (Seljak et al.
2003)
Temperature
85% of sky
cosmic variance
Best fit model
1 deg
Temperaturepolarization
CBI Results

ACBAR, VSA also tests physics of damping tail
 Important confirmation of theory
 Improves parameter constraints
Readhead et al. (2004)
Astro-ph/0409569
Structure Formation
Model Predicts Universe
Today
SDSS Tegmark et al.
Astro-ph/0310723
Verde et al. (2003)
Consistent Parameters
WMAP+CBI+ All
ACBAR
CMB(Bond)
CMB+
2dFGRS
CMB+SDSS
(Tegmark)
Wb h 2
.023 + .001
.0230 + .0011
.023 + .001
.0232 + .0010
Wxh2
.117 + .011
.117 + .010
.121 + .009
.122 + .009
h
.73 + .05
.72 + .05
.73 + .03
.70 + .03
ns
.97 + .03
.967 + .029
.97 + .03
.977 + .03
s8
.83 + .08
.85 + .06
.84 + .06
.92 + .08
Zentner & Bullock
2003
Top Hat Collapse

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Focus on overdensity
Follow evolution of
isolated sphere

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Expansion
Turn-around
Virialization
Press-Schechter Formalism

Probability of being in
an overdense region

Halo Mass Function
Do Stars Form in the Halos?
•Can the gas cool?
•Metals usually dominate the cooling --- but there
are no metals
•Molecular hydrogen is the only significant
cooling in primordial gas
•Molecular hydrogen usually forms on
dust…but there is no dust
•Formation through H+
Numerical Simulation
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CDM initial conditions
Hydrodynamics
Gas chemistry
Radiative Transfer
Simulations usually
show the formation of
a single massive star
100 - 1000 solar masses
No fragmentation seen
Abel 2003
First Stars
 Massive

stars with no primordial metals
Very hot surface--- lots of ionizing photons
• Destroys H2 -- suppresses star formation

Short-lived
• Supernova explosions?


Shocks compress gas
Shocks accelerate cosmic rays-- Compton cool and
produce X-rays. X-rays ionize universe and produce H2
• Gamma-ray bursts?
• Enrich environment with metals
Can We Observe the First
Stars?
 Direct
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detection of high z objects
Galaxies
Gamma Ray Bursts
Quasar
 Remnants
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Low z stars
Chemical Contamination
 Reionization
Effects of Reionization on
CMB
 Temperature
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Power Spectrum
Suppression of fluctuations at l > 40
Generation of new fluctuations at l > 10
Generation of small scale fluctuations
 Polarization
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Generates large scale temperature
polarization correlation
Generates large scale polarizationpolarization correlation
Reionization and
Temperature Spectrum
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Suppression
exp(-2t)
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Suppression of small
scale fluctuations
Additional fluctuations
generated on large
scales
Degenerate with
variations in slope
CMB Polarization

CMB polarization can
be split into two
pieces: E and B
 Scattering converts
local temperature
quadrupole into E
signal
 Generates TE and EE
signal
EE Polarization Signal

Amplitude and peak
position sensitive to
reionization history
Holder & Hu 2003
Doppler Effect Contribution
•Vanishes to linear order (except at
the largest scales)
•Doesn’t vanish to 2nd order
(Ostriker-Vishniac effect)
•Inhomogeneous reionization leads to
additional fluctuations
Why Is Polarization Difficult to
Observe?

Weak signal
 signal is statistical rather than a detection in
each pixel
 Foregrounds
 Synchrotron (dominant)
 Dust
 Systematic Uncertainties
WMAP Results

Significant uncertainty in
reionization redshift
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Will improve with more data
Polarization auto-correlation
Dt/t~0.1 in 4 year data
Current Estimate of Optical
Depth
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Significant uncertainty
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Temperature data pushes fit towards low tau
Polarization data pushes fit towards high tau
ACT:The Next
Step

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
Atacama Cosmology
Telescope
Funded by NSF
Will measure CMB
fluctuations on small
angular scales
Probe the primordial
power spectrum and the
growth of structure
ACT COLLABORATIONS
Government Labs
PENN
CatÓlica
Haverford
Schools
Museums
Princeton
Toronto
CUNY
…united through research, education and public outreach.
Simulations of mm-wave data.
1%
1.4
Survey area
0
 2%
High quality area
150 GHz
SZ Simulation
MAP
MBAC on ACT
1.7’ beam
2X noise
PLANCK
PLANCK
Where will we
be with CMB
Bond et al.
astro-ph/046195
Cosmic Timeline for ACT Science
• First galaxies
• Universe is reionized
• Ostriker-Vishniac/KSZ
• Extraction of
cosmological
parameters
• Initial conditions for
structure formation
z = 1000
t = 4 x 104 yrs
Primary CMB
• Surveys of Sunyaev-Zel’dovich (SZ) clusters
• Diffuse thermal SZ
• N(mass,z) – Evolution of Cosmic Structure
• Lensing of the CMB
• The growth of structure is sensitive to w and mn
• Additional cross-checks from correlations among effects
z=7
t = 3 x 106 yrs
CMB Lensing
z=1
t = 1 x 109 yrs
OV/KSZ
Diffuse Thermal SZ
z = .25
t = 12 x 109 yrs
now
Cluster Surveys
Sunyaev-Zel’dovich (SZ) clusters
Telectron = 108 K
Coma Cluster
e-
ee-
eee-
ee-
e-
Optical:
mm-Wave: SZ –
X-ray Flux:
Redshift and Mass
Compton Scattering
Mass
SZ Signature
Hot electron gas
imposes a unique
spectral signature
145 GHz
decrement
220 GHz
null
270 GHz
increment
NO SZ Contribution in Central Band
1.4°x 1.4°
Coordinated Cluster
Measurements
Galaxy Cluster
Identify and measure
>500 clusters in an
unbiased survey with
multi-wavelength
observations
HOT Electrons
limits of 3 x 1014 estimated from simulations
• Science derived from N(mass,z)
• Mass
Lensing of the CMB
• Lensing arises from integrated
mass fluctuations along the line
of sight.
-1850
(K)
• The CMB acts as a fixed
distance source, removing the
degeneracy inherent to other
lensing measurements.
0
• Signal at l = 1000-3000
• Image distortion – only a
minor effect in the power
spectrum.
• Must have a deep, high
fidelity map to detect this
effect.
1820
CMB
1.4°x 1.4°
Lensing of the CMB
-34
(K)
• RMS signal well above
noise floor.
• Isolate from SZ and point
sources spectrally.
0
• Identify with distinctive
4-point function.
34
Lensing Signal
2% of CMB RMS
1.4°x 1.4°
Cross-Correlating Lensing
and CMB
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CMB provides a source plane at z = 1100 with
very well determined statistical properties (but
poorer statistics)
CMB + Quasar & Galaxy Counts will measure
bias
CMB lensing+ Galaxy lensing crosscorrelation improves parameter
measurements by roughly a factor of 3
(Mustapha Ishak)
CMB +
SN
Add Lensing
CMB +
Lensing
X-correlate
ACT \REGION: Target for
future lensing surveys
ACT will begin surveying in 2006
We already plan deep multi-band
imaging with SALT of low extinction
part of ACT strip (200 square degrees)
Would be a very interesting target for
a lensing survey
ACT is but one of several next
generation CMB experiments

APEX (Atacama
Pathfinder Experiment)

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UCB/MPI
1.4mm and 2 mm obs.
SZ science
SPT (South Pole
Telescope)
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8m at South Pole
Chicago group (2008)
Large area
• Optimized for SZ/clusters
CMB Observations are an important
cosmological tool

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Large angle observations have helped solidify a
“standard model of cosmology” that fits a host of
astronomical observations
Small angle observations use this CMB backlight to
probe the emergence of structure
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First stars: OV effect, polarization
Cluster properties: SZ effect
Distribution of mass: lensing