Big Bang, and the Cosmic Microwave Background Eiichiro Komatsu - - PowerPoint PPT Presentation

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Big Bang, and the Cosmic Microwave Background Eiichiro Komatsu (Max-Planck-Institut fr Astrophysik, Garching) Celebration for the continuation of the Universe Cluster Deutsches Museum, November 22, 2012 1 Cosmology: The Questions How much

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Big Bang, and the Cosmic Microwave Background

Eiichiro Komatsu (Max-Planck-Institut für Astrophysik, Garching) Celebration for the continuation of the Universe Cluster Deutsches Museum, November 22, 2012

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Cosmology: The Questions

  • How much do we understand our Universe?
  • How old is it?
  • How big is it?
  • What shape does it take?
  • What is it made of?
  • How did it begin?

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The Breakthrough

  • Now we can observe the physical condition of the

Universe when it was very young.

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Cosmic Microwave Background (CMB)

  • Fossil light of the Big Bang!

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From “Cosmic Voyage”

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Night Sky in Optical (~0.5µm)

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Night Sky in Microwave (~1mm)

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Night Sky in Microwave (~1mm)

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Ttoday=2.725K

COBE Satellite, 1989-1993

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Spectrum of CMB

4K Black-body 2.725K Black-body 2K Black-body Rocket (COBRA) Satellite (COBE/FIRAS) CN Rotational Transition Ground-based Balloon-borne Satellite (COBE/DMR)

Wavelength

3mm 0.3mm 30cm 3m

Brightness, W/m2/sr/Hz

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(from Samtleben et al. 2007)

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Arno Penzias & Robert Wilson, 1965

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  • Isotropic
  • Unpolarized
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“For their discovery of cosmic microwave background radiation”

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  • P. Roll and D. Wilkinson, 1966

D.Wilkinson (W of WMAP)

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  • The spectrum of CMB has a peak at 1.1mm.
  • Let’s compare it with…

–Microwave oven: 12cm –Cellular phone: 20cm –UHF Television: 39-64cm –FM radio: 3m –AM radio: 300m

You can “see” CMB by TV (not by a cable TV of course!). Perhaps you can “hear” CMB by a cell phone?

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  • Dr. Hiranya Peiris

University College London

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How was CMB created?

  • When the Universe was hot, it was a hot soup made of:
  • Protons, electrons, and helium nuclei
  • Photons and neutrinos
  • Dark matter (DM)
  • DM does not do much, except for providing a a

gravitational potential because ρDM/ρH,He~5

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Universe as a hot soup

  • Free electrons can

scatter photons efficiently.

  • Photons cannot go

very far. proton helium electron photon

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Recombination and Decoupling

  • [recombination]

When the temperature falls below 3000 K, almost all electrons are captured by protons and helium nuclei.

  • [decoupling] Photons

are no longer

  • scattered. I.e., photons

and electrons are no longer coupled. Time 1500K 6000K

3000K

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proton helium electron photon

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COBE/DMR, 1992

  • Isotropic?
  • CMB is anisotropic! (at the 1/100,000

level)

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Smoot et al. (1992)

1cm 6mm 3mm

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SLIDE 19

“For their discovery of the blackbody form and anisotropy

  • f the cosmic microwave background radiation”

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CMB: The Farthest and Oldest Light That We Can Ever Hope To Observe Directly

  • When the Universe was 3000K (~380,000 years after the Big Bang),

electrons and protons were combined to form neutral hydrogen.

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WMAP at Lagrange 2 (L2) Point

  • L2 is a million miles from Earth
  • WMAP leaves Earth, Moon, and Sun

behind it to avoid radiation from them

June 2001: WMAP launched!

February 2003: The first-year data release March 2006: The three-year data release March 2008: The five-year data release January 2010: The seven-year data release

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used to be September 8, 2010: WMAP left L2

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WMAP at Lagrange 2 (L2) Point

  • L2 is a million miles from Earth
  • WMAP leaves Earth, Moon, and Sun

behind it to avoid radiation from them

June 2001: WMAP launched!

February 2003: The first-year data release March 2006: The three-year data release March 2008: The five-year data release January 2010: The seven-year data release

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used to be September 8, 2010: WMAP left L2

We are currently working

  • n the final data release!

(nine-year data release)

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WMAP WMAP Spacecraft Spacecraft

thermally isolated instrument cylinder secondary reflectors focal plane assembly feed horns back to back Gregorian optics, 1.4 x 1.6 m primaries upper omni antenna line of sight deployed solar array w/ web shielding medium gain antennae passive thermal radiator warm spacecraft with:

  • instrument electronics
  • attitude control/propulsion
  • command/data handling
  • battery and power control

60K 90K

300K

Radiative Cooling: No Cryogenic System

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COBE to WMAP (x35 better resolution)

COBE WMAP

COBE 1989 WMAP 2001

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WMAP 7-Year Science Team

  • C.L. Bennett
  • G. Hinshaw
  • N. Jarosik
  • S.S. Meyer
  • L. Page
  • D.N. Spergel
  • E.L. Wright
  • M.R. Greason
  • M. Halpern
  • R.S. Hill
  • A. Kogut
  • M. Limon
  • N. Odegard
  • G.S. Tucker
  • J. L.Weiland
  • E.Wollack
  • J. Dunkley
  • B. Gold
  • E. Komatsu
  • D. Larson
  • M.R. Nolta
  • K.M. Smith
  • C. Barnes
  • R. Bean
  • O. Dore
  • H.V. Peiris
  • L.

Verde

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Cosmic Pie Chart: 7-year

  • Standard Model
  • H&He = 4.58% (±0.16%)
  • Dark Matter = 22.9% (±1.5%)
  • Dark Energy = 72.5% (±1.6%)
  • H0=70.2±1.4 km/s/Mpc
  • Age of the Universe = 13.76 billion

years (±0.11 billion years)

“ScienceNews” article on the WMAP 7-year results

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How did we obtain these numbers?

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23 GHz [unpolarized]

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33 GHz [unpolarized]

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41 GHz [unpolarized]

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61 GHz [unpolarized]

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94 GHz [unpolarized]

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How many components?

  • 1. CMB: Tν~ν0
  • 2. Synchrotron (electrons going around magnetic

fields): Tν~ν–3

  • 3. Free-free (electrons colliding with protons): Tν~ν–2
  • 4. Dust (heated dust emitting thermal emission): Tν~ν2
  • 5. Spinning dust (rapidly rotating tiny dust grains):

Tν~complicated You need at least five frequencies to separate them!

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Galaxy-cleaned Map

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Analysis: 2-point Correlation

  • C(θ)=(1/4π)∑(2l+1)ClPl(cosθ)
  • How are temperatures on two

points on the sky, separated by θ, are correlated?

  • “Power Spectrum,” Cl

– How much fluctuation power do we have at a given angular scale? – l~180 degrees / θ

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θ

COBE WMAP

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COBE/DMR Power Spectrum Angle ~ 180 deg / l

Angular Wavenumber, l

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~9 deg ~90 deg (quadrupole)

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COBE To WMAP

  • COBE is unable to resolve the

structures below ~7 degrees

  • WMAP’s resolving power is 35

times better than COBE.

  • What did WMAP see?

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θ

COBE WMAP

θ

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WMAP Power Spectrum

Angular Power Spectrum Large Scale Small Scale about 1 degree

  • n the sky

COBE

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The Cosmic Sound Wave

  • “The Universe as a Miso soup”
  • Main Ingredients: protons, helium nuclei, electrons, photons
  • We measure the composition of the Universe by

analyzing the wave form of the cosmic sound waves.

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CMB to Baryon & Dark Matter

  • 1-to-2: baryon-to-photon ratio
  • 1-to-3: matter-to-radiation ratio (zEQ: equality redshift)

Baryon Density (Ωb) Total Matter Density (Ωm) =Baryon+Dark Matter

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CMB Polarization

  • CMB is (very weakly) polarized!

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“Stokes Parameters”

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Q<0; U=0 North East

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23 GHz [polarized]

Stokes Q Stokes U

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23 GHz [polarized]

Stokes Q Stokes U North East

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33 GHz [polarized]

Stokes Q Stokes U

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41 GHz [polarized]

Stokes Q Stokes U

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61 GHz [polarized]

Stokes Q Stokes U

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94 GHz [polarized]

Stokes Q Stokes U

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How many components?

  • 1. CMB: Tν~ν0
  • 2. Synchrotron (electrons going around magnetic

fields): Tν~ν–3

  • 3. Free-free (electrons colliding with protons): Tν~ν–2
  • 4. Dust (heated dust emitting thermal emission): Tν~ν2
  • 5. Spinning dust (rapidly rotating tiny dust grains):

Tν~complicated You need at least THREE frequencies to separate them!

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Physics of CMB Polarization

  • CMB Polarization is created by a local temperature

quadrupole anisotropy.

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Wayne Hu

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Stacking Analysis

  • Stack polarization

images around temperature hot and cold spots.

  • Outside of the Galaxy

mask (not shown), there are 12387 hot spots and 12628 cold spots.

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Radial and Tangential Polarization Patterns around Temp. Spots

  • All hot and cold spots are stacked
  • “Compression phase” at θ=1.2 deg and

“slow-down phase” at θ=0.6 deg are predicted to be there and we observe them!

  • The overall significance level: 8σ

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E-mode and B-mode

  • Gravitational potential

can generate the E- mode polarization, but not B-modes.

  • Gravitational

waves can generate both E- and B-modes!

B mode E mode

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Gravitational waves are coming toward you... What do you do?

  • Gravitational waves stretch

space, causing particles to move.

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Two Polarization States of GW

  • This is great - this will automatically

generate quadrupolar anisotropy around electrons!

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From GW to CMB Polarization

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Electron

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From GW to CMB Polarization

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Redshift Redshift Blueshift Blueshift R e d s h i f t R e d s h i f t B l u e s h i f t B l u e s h i f t

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From GW to CMB Polarization

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Gravitational waves can produce both E- and B-mode polarization

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“Tensor-to-scalar Ratio,” r

r = [Power in Gravitational Waves] / [Power in Gravitational Potential]

Theory of “Cosmic Inflation” predicts r <~ 1 – I will come back to this in a moment

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SLIDE 59
  • No detection of B-mode polarization yet.

B-mode is the next holy grail!

Polarization Power Spectrum

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Theory of the Very Early Universe

  • The leading theoretical idea about the primordial Universe,

called “Cosmic Inflation,” predicts:

  • The expansion of our Universe accelerated in a tiny

fraction of a second after its birth.

  • Just like Dark Energy accelerating today’s expansion: the

acceleration also happened at very, very early times!

  • Inflation stretches “micro to macro”
  • In a tiny fraction of a second, the size of an atomic nucleus

(~10-15m) would be stretched to 1 A.U. (~1011m), at least.

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(Guth 1981; Linde 1982; Albrecht & Steinhardt 1982; Starobinsky 1980)

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Cosmic Inflation = Very Early Dark Energy

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Origin of Fluctuations

  • OK, back to the cosmic hot soup.
  • The sound waves were created when we perturbed it.
  • “We”? Who?
  • Who actually perturbed the cosmic soup?
  • Who generated the original (seed) ripples?

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WMAP Power Spectrum

Angular Power Spectrum Large Scale Small Scale about 1 degree

  • n the sky

COBE

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SLIDE 64

Getting rid of the Sound Waves

Angular Power Spectrum

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Primordial Ripples

Large Scale Small Scale

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The Early Universe Could Have Done This Instead

Angular Power Spectrum

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More Power on Large Scales

Small Scale Large Scale

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...or, This.

Angular Power Spectrum

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More Power on Small Scales

Small Scale Large Scale

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...or, This.

Angular Power Spectrum

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Small Scale Large Scale

Parametrization: l(l+1)Cl ~ lns–1 And, inflation predicts ns~1

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Theory Says...

  • The leading theoretical idea about the primordial Universe,

called “Cosmic Inflation,” predicts:

  • The expansion of our Universe accelerated in a tiny

fraction of a second after its birth.

  • the primordial ripples were created by quantum

fluctuations during inflation, and

  • how the power is distributed over the scales is

determined by the expansion history during cosmic inflation.

  • Measurement of ns gives us this remarkable information!

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Stretching Micro to Macro

Macroscopic size at which gravity becomes important δφ Quantum fluctuations on microscopic scales INFLATION! Quantum fluctuations cease to be quantum, and become observable! δφ

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Inflation Offers a Magnifier for Microscopic World

  • Using the power spectrum of primordial fluctuations

imprinted in CMB, we can observe the quantum phenomena at the ultra high-energy scales that would never be reached by the particle accelerator.

  • Measured value: ns = 0.968 ± 0.012 (68%CL)

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  • Quantum fluctuations also generate ripples in space-

time, i.e., gravitational waves, by the same mechanism.

  • Primordial gravitational waves generate temperature

anisotropy in CMB, as well as polarization in CMB with a distinct pattern called “B-mode polarization.” h = (Expansion Rate)/(21/2πMplanck) [in natural units] [h = “strain”]

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(Tensor) Quantum Fluctuations, a.k.a. Gravitational Waves

Starobinsky (1979)

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Probing Inflation (2-point Function)

  • Joint constraint on the

primordial tilt, ns, and the tensor-to-scalar ratio, r.

  • r < 0.24 (95%CL)

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Summary

  • CMB is the fossil light of the Big Bang.
  • We could determine the age, composition, expansion

rate, etc., from CMB.

  • We could even push the boundary farther back in time,

probing the origin of fluctuations in the very early Universe: inflationary epoch at ultra-high energies.

  • Next Big Thing: Primordial gravitational waves.
  • The 3-point function: Powerful test of inflation.

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Bispectrum

  • Three-point function!
  • Bζ(k1,k2,k3)

= <ζk1ζk2ζk3> = (amplitude) x (2π)3δ(k1+k2+k3)F(k1,k2,k3)

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model-dependent function

k1 k2 k3 Primordial fluctuation ”fNL”

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SLIDE 75

MOST IMPORTANT

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Probing Inflation (3-point Function)

  • Inflation models predict that primordial fluctuations are very

close to Gaussian.

  • In fact, ALL SINGLE-FIELD models predict a particular form
  • f 3-point function to have the amplitude of fNL=0.02.
  • Detection of fNL>1 would rule out ALL single-field models!
  • No detection of 3-point functions of primordial curvature
  • perturbations. The 95% CL limits are:
  • –10 < fNL < 74
  • The WMAP data are consistent with the prediction of

simple single-field inflation models: 1–ns≈r≈fNL

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Trispectrum

  • Tζ(k1,k2,k3,k4)=(2π)3δ(k1+k2+k3+k4)

{gNL[(54/25)Pζ(k1)Pζ(k2)Pζ(k3)+cyc.] +τNL[Pζ(k1)Pζ(k2)(Pζ(|k1+k3|)+Pζ(|k1+k4|))+cyc.]} The local form consistency relation, τNL=(6/5)(fNL)2, may not be respected – additional test of multi-field inflation! k3 k4 k2 k1

gNL

k2 k1 k3 k4

τNL

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The diagram that you should take away from this talk.

  • The current limits

from WMAP 7-year are consistent with single-field or multi- field models.

  • So, let’s play around

with the future.

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ln(fNL) ln(τNL) 74 3.3x104

(Smidt et

  • al. 2010)
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Case A: Single-field Happiness

  • No detection of

anything after

  • Planck. Single-field

survived the test (for the moment: the future galaxy surveys can improve the limits by a factor of ten). ln(fNL) ln(τNL) 10 600

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Case B: Multi-field Happiness

  • fNL is detected. Single-

field is dead.

  • But, τNL is also

detected, in accordance with the Suyama-Yamaguchi inequality, as expected from most (if not all - left unproven) of multi- field models. ln(fNL) ln(τNL) 600

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Case C: Madness

  • fNL is detected. Single-

field is dead.

  • But, τNL is not

detected, inconsistent with the Suyama- Yamaguchi inequality.

  • (With the caveat that

this may not be completely general) BOTH the single-field and multi-field are gone. ln(fNL) ln(τNL) 30 600

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Planck Launched!

  • The Planck satellite was successfully launched from French

Guiana on May 14, 2009.

  • Separation from the Herschell satellite was also successful.
  • Planck has mapped the full sky already - results expected to be

released in December, 2012.

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Planck: Expected ClTemperature

  • WMAP: l~1000 => Planck: l~3000

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Planck: Expected ClPolarization

  • (Above) E-modes
  • (Left) B-modes (r=0.3)

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