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Title: Cosmology: Answers and Questions


1
Cosmology Answers and Questions
  • David Spergel
  • Princeton University

2
We now have a 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
  • Adiabatic, scale invariant, Gaussian Fluctuations
  • Harrison-Zeldovich-Peebles
  • Inflationary models

3
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

4
Thermal History of Universe
NEUTRAL
radiation
matter
r
IONIZED
103
104
z
5
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)

6
Sunyaev Zeldovich
7
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8
CMB Overview
  • We can detect both CMB temperature and
    polarization fluctuations
  • Polarization Fluctuations can be decomposed into
    E and B modes

q 180/l
9
ADIABATIC DENSITY FLUCTUATIONS
10
ISOCURVATURE ENTROPY FLUCTUATIONS
11
Determining Basic Parameters
Baryon Density Wbh2 0.015,0.017..0.031 also
measured through D/H
12
Determining Basic Parameters
Matter Density Wmh2 0.16,..,0.33
13
Determining Basic Parameters
Angular Diameter Distance w -1.8,..,-0.2 When
combined with measurement of matter density
constrains data to a line in Wm-w space
14
Predictive Theory Motivates Precision Measurements
  • COBE measurement of spectrum (1990) and detection
    of large scale fluctuations (1992)
  • Detection of first acoustic peak (TOCO Miller et
    al. 1999)
  • Rapidly improving ground and balloon-based
    measurements (1999-2002)
  • First peaks (TOCO, BOOM, DASI, )
  • EE (DASI)
  • Wilkinson Microwave Anisotropy Probe (2003)
  • TT TE

15
Wilkinson Microwave Anisotropy Probe
A partnership between NASA/GSFC and Princeton
Science Team
NASA/GSFC Chuck Bennett (PI) Michael Greason Bob
Hill Gary Hinshaw Al Kogut Michele Limon Nils
Odegard Janet Weiland Ed Wollack
Brown Greg Tucker
UCLA Ned Wright
Princeton Chris Barnes Norm Jarosik Eiichiro
Komatsu Michael Nolta
Chicago Stephan Meyer
UBC Mark Halpern
Lyman Page Hiranya Peiris David Spergel Licia
Verde
16
WMAP Spacecraft
upper omni antenna
back to back
line of sight
Gregorian optics,
1.4 x 1.6 m primaries
60K
passive thermal radiator
focal plane assembly
feed horns
secondary
90K
reflectors
thermally isolated
instrument cylinder
300K
warm spacecraft with
medium gain antennae
- instrument electronics
- attitude control/propulsion
- command/data handling
deployed solar array w/ web shielding
- battery and power control
MAP990422
17
WMAP Design Goal Minimize Systematics
  • Differential design
  • milliK thermal Stability
  • Multiply linked scan pattern
  • Many cross-checks possible within data set

A-B-A-B
B-A-B-A
One of 20
18
June 30, 2001
19
K - 22GHz
20
Ka - 33GHz
21
Q - 41GHz
22
V - 61GHz
23
W - 94GHz
24
W - 94GHz
25
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26

27
Q band V band W band
28
Foregrounds
  • Synchrotron
  • Drops off sharply with n
  • Dust
  • Finkbeiner Davis Schlegel template good fit
  • Free-Free
  • H a surveys (WHAM, VTSS, SHASSA)
  • Point sources
  • Measured through skewness
  • Multifrequency power spectrum
  • Extrapolate source counts

29
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30
FOREGROUND CORRECTED MAP
31
Angular Power Spectrum is Robust
  • Same results for 28 different channel
    combinations
  • Same results for auto and cross-correlations
  • Same results for different weightings, analysis
    schemes

32
Temperature
85 of sky
cosmic variance
Best fit model
1 deg
Temperature-polarization
33
Simple Model Fits CMB data
Readhead et al. astro/ph 0402359
34
CMB BBN
  • CMB measures baryon/photon ratio
  • Determines D/H ratio
  • Helium
  • Was discrepant with CMB and D/H
  • New neutron lifetime measurement removes problem
  • Lithium
  • Sensitive to chemical evolution of Deuterium
  • Early destruction

35
Model Predicts Universe Today
SDSS Tegmark et al. Astro-ph/0310723
Verde et al. (2003)
36
Evolution from Initial Conditions I
WMAP team assembled
WMAP completes 2 year of observations!
DA leave Princeton
WMAP at Cape
37
Evolving Initial Conditions II
Verde et al.
38
Evolution from Initial Conditions III
Verde et al.
39
Consistent Parameters
WMAPCBIACBAR All CMB(Bond) CMB 2dFGRS CMBSDSS (Tegmark)
Wbh2 .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
40
Consistency!
CMB Lensing Contaldi et al. (2003)
  • Hubble Constant
  • Baryon Abundance
  • Lensing Amplitude
  • Supernova Distance Scale
  • Cluster Abundances
  • Stellar Ages
  • Helium Abundance

s8
W
Spergel et al. 2003
41
New Questions
  • Physics that we dont know (String theory,
    quantum cosmology,
  • How did the universe begin?
  • What is the dark energy?
  • Physics that we dont know how to calculate
    (Non-linear hydro, star formation
  • First stars
  • Galaxy formation

42
Probing the Dark Energy
  • Detected only through Friedman equation

?
43
How Can We Measure a(t)?
  • Standard Ruler (angular diameter distance)
  • CMB peak positions
  • Matter power spectrum
  • Standard Candle
  • Supernova
  • Growth Rate of Structure
  • Gravitational Lensing

44
Baryon Oscillations
CMB
C(q)
Baryon oscillation scale
q
1o
Galaxy Survey
Limber Equation
C(q)
(weaker effect)
Selection function
q
photo-z slices
45
Baryon Oscillations as a Standard Ruler
  • In a redshift survey, we can measure correlations
    along and across the line of sight.
  • Yields H(z) and DA(z)!
  • Alcock-Paczynski Effect

46
SDSS and Baryon Wiggles
  • Purely geometric test
  • (SDSS WMAP)

Eisenstein et al. (2005)
47
What is the dark energy?
CMB data consistent with other data sets if w is
near -1 (dark energy is a cosmological constant)
-1.0
-1.0
-1.0
-1.0
48
Current Constraints
Seljak et al. 2004
49
ACTThe Next Step
  • Atacama Cosmology Telescope
  • Funded by NSF
  • Will measure CMB fluctuations on small angular
    scales
  • Probe the primordial power spectrum and the
    growth of structure

50
ACT COLLABORATIONS
Government Labs
Museums
Schools
united through research, education and public
outreach.
51
Simulations of mm-wave data.
Survey area
High quality area
150 GHz
SZ Simulation
MBAC on ACT 1.7 beam
PLANCK
2X noise
MAP
PLANCK
52
Where will we be with CMB
Bond et al. astro-ph/046195
53
Cosmic Timeline for ACT Science
  • First galaxies
  • Universe is reionized
  • Ostriker-Vishniac/KSZ
  • Surveys of Sunyaev-Zeldovich (SZ) clusters
  • Diffuse thermal SZ

Cosmic Microwave Background
  • 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
  • Initial conditions for structure formation
  • Extraction of cosmological parameters

now
z 1000 t 4 x 104 yrs
z 7 t 3 x 106 yrs
z 1 t 1 x 109 yrs
z .25 t 12 x 109 yrs
Primary CMB CMB Lensing
OV/KSZ Diffuse Thermal SZ Cluster Surveys
54
Sunyaev-Zeldovich (SZ) clusters
Coma Cluster
Telectron 108 K
e-
e-
e-
e-
e-
e-
e-
Cosmic Microwave Background
e-
e-
X-ray Flux Mass
Optical Redshift and Mass
mm-Wave SZ Compton Scattering
55
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
1.4x 1.4
56
Coordinated Cluster Measurements
Identify and measure gt500 clusters in an unbiased
survey with multi-wavelength observations
Galaxy Cluster
Cosmic Microwave Background
HOT Electrons
  • Mass limits of 3 x 1014 estimated from
    simulations
  • Science derived from N(mass,z)

57
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58
Lensing of the CMB
-1850 (?K) 0 1820
  • Lensing arises from integrated mass fluctuations
    along the line of sight.
  • The CMB acts as a fixed distance source,
    removing the degeneracy inherent to other
    lensing measurements.
  • 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.

1.4x 1.4
59
Lensing of the CMB
-34 (?K) 0 34
  • RMS signal well above noise floor.
  • Isolate from SZ and point sources spectrally.
  • Identify with distinctive 4-point function.

Lensing Signal
2 of CMB RMS
1.4x 1.4
60
Cross-Correlating Lensing and CMB
  • 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 cross-correlation
    improves parameter measurements by roughly a
    factor of 3 (Mustapha Ishak)

CMB SN
Add Lensing
CMB Lensing
X-correlate
61
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
62
Cosmology Now Has A Standard Model
  • Basic parameters are accurately determined
  • Many can be measured using multiple techniques
  • CMB best fit now consistent with other
    measurements
  • Mysteries remain dark matter, dark energy,
    physics of inflation
  • Next step
  • Probe Physics Beyond the Standard Model

63
THANK YOU !
64
CMB Polarization
  • Weak signal
  • signal is statistical rather than a detection in
    each pixel
  • Foregrounds
  • Synchrotron (dominant)
  • Dust
  • Systematic Uncertainties
  • Significant uncertainty in reionization redshift
  • Will improve with more data
  • Polarization auto-correlation
  • Dt/t0.1 in 4 year data

65
Polarization Measurements
  • New window into Early Universe
  • Gravity waves from inflation
  • Reionization
  • Constraints on isocurvature admixtures,
    ionization history, etc.
  • CMB Polarization Measurements
  • Upcoming WMAP release
  • BOOMERANG Polarization flight
  • Lots of exciting ground and balloon experiments
    under development
  • Planck
  • CMBPOL

66
CMB Polarization Another Dark Energy Probe
  • When combined with optical measurements, this
    will enable us to cleanly measure the growth rate
    of structure an independent probe of the
    properties of the dark energy
  • Polarization lensing/ISW cross-correlation will
    enable us to probe the properties of dark energy
    at z5-50 -- an epoch inaccessible to other
    experiments
  • Small scale polarization experiments point the
    way towards the detection of gravity waves

67
W - 94GHz
68
Is the Universe Finite or Infinite?
69
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70
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71
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72
Topology
73
Two Torus
74
Other Tilings
75
Three Torus
Same idea works in three space dimensions
76
Infinite number of tiling patterns
This one only works in hyperbolic space
77
Spherical Topologies
This example only works in spherical space
78
Dodecahedral Space
Tiling of the three-sphere by 120 regular
dodecahedrons
79
Homogeneous Isotropic Universe
80
The microwave background in a multi-connected
universe
81
Matched circles in a three torus universe
82
If the universe was finite
Cornish, Spergel, Starkman, Komatsu
83
What we see in the WMAP data
UNIVERSE IS BIG!
84
Conclusions
  • Cosmology is in a golden age!
  • Advances in technology are enabling us to probe
    the physics of the very early universe and the
    birth of structure
  • So far, the standard model appears to fit the
    data, but stay tuned!

85
Pen, Seljak, Turok astro-ph/974231
ACTIVE ISOCURVATURE MODELS
86
Key Historical Papers
  • Acoustic Peaks
  • Sunyaev Zeldovich, ApSS, 7, 3 (1970)
  • Peebles Yu, ApJ 162, 815 (1970)
  • CDM
  • Peebles ApJ 263, L1 (1982) proposed cold dark
    matter
  • Lambda
  • Gunn Tinsley (1975)
  • Turner, Steigman Krauss (1984)
  • Peebles ApJ 284, 439 (1984)
  • Supernova papers

87
Key Technological StepRevolutionary CMB Cameras
(multiplexed, filled arrays of thousands of
bolometers)
  • Planning three 1024-element arrays for fine-scale
    CMB on ACT the MBAC.
  • Propose 4000-element polarized camera for ACT to
    round-out science return via lensing and
    inflationary probe.

32 mm
1 mm
SHARC II 12x32 Popup Array
One element of array
88
Too Many Bumps and Wiggles?
  • C2 1.08 (3 probability)
  • Need to include several systematic effects in
    error budget
  • Lensing of CMB
  • Beam variations asymmetries
  • 1/f noise non-Gaussian contribution to 4pt

89
More to Come.
  • WMAP has effectively no lifetime limit
  • Approved for 4 years of operation
  • Improved TE EE data will significantly improve
    t measurement
  • More accurate 2nd and 3rd peaks
  • Calibrate ground-based high l measurements
  • Improvements in complementary measurements (SDSS,
    supernovaACS, Carnegie, NOAO)

0.30 0.20 0.10 0,00
t
0.90 0.95 1.00 1.05 1.10
ns
90
Ground Based High Resolution Surveys
  • Sunyaev-Zeldovich detections of clusters and hot
    intercluster gas
  • Ostriker-Vishniac fluctuations from z5-20 from
    motions of reionized gas
  • Gravitational Lensing of CMB
  • Correlates with optical surveys, quasars
  • Probes mass fluctuations along line of sight

91
Too Little Large Scale Power?
  • Lack of large scale power
  • Seen in COBE but clearer now
  • Is the universe finite?
  • Are we seeing a characteristic scale?
  • Is it just chance?

92
LCDM Best Fit Parameters
93
Wilkinson Microwave Anisotropy Probe
A partnership between NASA/GSFC and Princeton
Science Team
NASA/GSFC Chuck Bennett (PI) Michael Greason Bob
Hill Gary Hinshaw Al Kogut Michele Limon Nils
Odegard Janet Weiland Ed Wollack
Brown Greg Tucker
UCLA Ned Wright
Princeton Chris Barnes Norm Jarosik Eiichiro
Komatsu Michael Nolta
Chicago Stephan Meyer
UBC Mark Halpern
Lyman Page Hiranya Peiris David Spergel Licia
Verde
94
WMAP Spacecraft
upper omni antenna
back to back
line of sight
Gregorian optics,
1.4 x 1.6 m primaries
60K
passive thermal radiator
focal plane assembly
feed horns
secondary
90K
reflectors
thermally isolated
instrument cylinder
300K
warm spacecraft with
medium gain antennae
- instrument electronics
- attitude control/propulsion
- command/data handling
deployed solar array w/ web shielding
- battery and power control
MAP990422
95
WMAP Design Goal Minimize Systematics
  • Differential design
  • milliK thermal Stability
  • Multiply linked scan pattern
  • Many cross-checks possible within data set

A-B-A-B
B-A-B-A
One of 20
96
June 30, 2001
97
K - 22GHz
98
Ka - 33GHz
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