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Cosmology Answers and Questions

- David Spergel
- Princeton University

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

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

NEUTRAL

radiation

matter

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)

Sunyaev Zeldovich

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CMB Overview

- We can detect both CMB temperature and

polarization fluctuations - Polarization Fluctuations can be decomposed into

E and B modes

q 180/l

ADIABATIC DENSITY FLUCTUATIONS

ISOCURVATURE ENTROPY FLUCTUATIONS

Determining Basic Parameters

Baryon Density Wbh2 0.015,0.017..0.031 also

measured through D/H

Determining Basic Parameters

Matter Density Wmh2 0.16,..,0.33

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

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

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

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

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

June 30, 2001

K - 22GHz

Ka - 33GHz

Q - 41GHz

V - 61GHz

W - 94GHz

W - 94GHz

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5º

Q band V band W band

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

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FOREGROUND CORRECTED MAP

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

Temperature

85 of sky

cosmic variance

Best fit model

1 deg

Temperature-polarization

Simple Model Fits CMB data

Readhead et al. astro/ph 0402359

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

Model Predicts Universe Today

SDSS Tegmark et al. Astro-ph/0310723

Verde et al. (2003)

Evolution from Initial Conditions I

WMAP team assembled

WMAP completes 2 year of observations!

DA leave Princeton

WMAP at Cape

Evolving Initial Conditions II

Verde et al.

Evolution from Initial Conditions III

Verde et al.

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

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

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

Probing the Dark Energy

- Detected only through Friedman equation

?

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

Baryon Oscillations

CMB

C(q)

Baryon oscillation scale

q

1o

Galaxy Survey

Limber Equation

C(q)

(weaker effect)

Selection function

q

photo-z slices

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

SDSS and Baryon Wiggles

- Purely geometric test
- (SDSS WMAP)

Eisenstein et al. (2005)

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

Current Constraints

Seljak et al. 2004

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

ACT COLLABORATIONS

Government Labs

Museums

Schools

united through research, education and public

outreach.

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

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

- 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

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

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

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)

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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

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

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

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

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

THANK YOU !

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

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

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

W - 94GHz

Is the Universe Finite or Infinite?

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Topology

Two Torus

Other Tilings

Three Torus

Same idea works in three space dimensions

Infinite number of tiling patterns

This one only works in hyperbolic space

Spherical Topologies

This example only works in spherical space

Dodecahedral Space

Tiling of the three-sphere by 120 regular

dodecahedrons

Homogeneous Isotropic Universe

The microwave background in a multi-connected

universe

Matched circles in a three torus universe

If the universe was finite

Cornish, Spergel, Starkman, Komatsu

What we see in the WMAP data

UNIVERSE IS BIG!

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!

Pen, Seljak, Turok astro-ph/974231

ACTIVE ISOCURVATURE MODELS

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

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

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

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

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

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?

LCDM Best Fit Parameters

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

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

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

June 30, 2001

K - 22GHz

Ka - 33GHz