04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND ObservationalObservational Cosmology:Cosmology: 2.2.TheThe CosmicCosmic BackgroundBackground
“My goal is simple. It is complete understanding of the universe, why it as it is and why it exists as all.” — Stephen Hawking. 1 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.1:2.1: TheThe IsotropicIsotropic BackgroundBackground Is the Universe really homogeneous & isotropic ?? - Olbers Paradox revisited Heinrich Olbers 1826 (Thomas Digges 1576) WHYWHY ISIS THETHE SKYSKY SOSO DARKDARK ?? TheThe SkySky shouldshould bebe thethe averageaverage surfacesurface brightnessbrightness ofof aa starstar !!!!!!
Solution: The Universe has a finite age ➠ Not all the light has had time to reach us yet !
This is the optical Olbers Paradox…. BUT … What if Mr Olber had microwave eyes ?
The sky would be uniformly bright at λ=5cm At a constant temperature of 2.73K 2 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.1:2.1: TheThe IsotropicIsotropic BackgroundBackground Is the real Universe really homogeneous and isotropic ??
Actual Temperature Distribution
1 / 1000 Temperature variation
1 / 100, 000 Temperature variation m c 4
3 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.1:2.1: TheThe IsotropicIsotropic BackgroundBackground The discovery of the microwave Background • 1964: Penzias & Wilson - • Bell Laboratries Satellite Telecommunications at microwave wavelengths ~ 7.35cm • Found a value of 3.5K higher temperature than expected when turning antenna to blank sky • Serendipitously discover the 2.73K microwave background radiation
These photons are the redshifted relic or ashes of the Big Bang Originally high energy gamma rays, these primordial photons have cooled to be 2.73K 2mm microwaves today 4 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground Recombination and Decoupling
BIG BANG
- - e γ e- γ e p p γ • matter in thermal equilibrium with e- p p γ the radiation. photons and electrons to interact via Thompson scattering t z recombination •Temperature drops then p+e-→H ➠ γ H recombination T γ H
R H H γ γ • Eventually interactions stop allowing the photons to flow freely on scales of the De-coupling H γ horizon ➠ de-coupling H γ H γ γ H γ • Era at which any photon last scattered off any electron surface of last scattering Last Scattering 5 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground
The Surface of Last Scattering
After Recombination and Decoupling the photons are no longer bound to matter and can stream freely Photons from the Big Bang fill the universe and we observe them as the 2.7K microwave background. These photons are the redshifted relic or ashes of the Big Bang Last time photons interacted ➠ Surface of Last Scattering This also means that we can not observe the Universe when it was younger than ~400,000 years
6 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground The Relic Background Energy density of radiation c 2 aT 4 c 2 aT 4 0.26MeVm−3 ~ 5x10−5 εγ = ργ = ⇒ εγ ,o = ρo = o ≈ ρc −3 −3 −4 Energy density of the matter a = radiation constant = 4.73x10 MeVm K 2 2 2 3Hoc −3 −3 εb,o = Ωb,oρcc ⇒ 0.04 € = 0.04(5200MeVm ) ≈ 208MeVm € 8πG
εγ ,o 8 −3 Photon Number Density nγ ,o ≈ ≈ 4x10 m hυ 2mm nb,o 0.22 −10 η = ≈ 8 ≈ 5.5x10 εb,o −3 n 4x10 € γ ,o Baryon Number density nb,o ≈ = 0.22m mproton € • Today : Energy density in Baryons is 800 times energy density in photons • But : Number density of Baryons €to photon is 1 in 109 € 7 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground The Physics of Recombination I. Ionization energy of Hydrogen =13.6eV Temperature drops then p+e-→H ➠ recombination ➠ depends on II. The baryon/photon ratio, η~5x10-10
But even at lower temperatures sufficient photons with appropriate ionization energy
n p = number of unbound protons n p n p ne n H = number of bound protons ➠ Therefore define the fractional ionization χ = = = n p + n H nb nb n b = number of baryons n e = number of electrons 3 / 2 m c 2 − H mH kT kT n H = gH 2 e Number densities of 2πh € 3 / 2 2 3 / 2 2 particles as a function m p c −3 / 2 (m H −m p −me )c mp kT − n g m kT − o kT H H H kT of T given by n p = gp 2 e = 2 e 2 n n g g m m 2 Boltzmann function πh p e p e p e πh 3 / 2 m c 2 m kT − e e kT ne = ge 2 e 2πh
2 −3 / 2 Q H binding energy = Q = (mp+me-mH)c n H mekT kT m ~ m SAHA EQUATION p H = 2 e Statistical weights€ mp= me=2, mH=4 n p ne 2πh 8
€ 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground The Physics of Recombination 1− χ n = n −3 / 2 Q H p 1 n m kT n p n p χ Saha H e kT Ionization χ = = ⇒ = e 3 Fraction n Equation 2 n p + n H nb p η = 2 n p ne 2πh χnγ
2 3 3 Black Body Energy 16π h ν dν 2.404 kT εBB (ν)dν = 3 hν / kT ⇒ nγ = 2 4 Density Distribution c e −1 π hc € €
Quadratic in χ 1 3 −3 / 2 Q € 1− χ kT kT 2 = 3.84 2 e 4 2 χ mec
Between temperatures of To~5000 ⇒ 2000, Ionization fraction drops 1 ⇒ 0 €
9 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground The Physics of Recombination
Decoupling Optical Depth
10 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.2:2.2: TheThe OriginOrigin ofof thethe MicrowaveMicrowave BackgroundBackground The Physics of Recombination Fractional Ionization as function of Temperature 1 0.01 0.0001 10-6 Ionization 10-8 χ(z) 10-10 10-12 10-14 Ionization 10-16 10-18 χ(T) 10-20 10-22 10-24 10-26 1250 2500 3750 5000 6250 7500 Temperature (K)
Epoch of Recombination (kT~Q) Epoch of Decoupling (Γ~H) To ~ 3740K To ~ 3000 z ~ 1370, Δz ~ 200 z ~ 1089, Δz ~ 195 T ~ 240kyr, Δt ~ 70kyr T ~ 379,000yr, Δt ~ 118ky 11 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Temperature Fluctuations
Observations of CMB ➠ Fluctuations in Temperature
Early Universe was highly homogenous
At the level of δT ~ 10-3 : Observe Dipole Anisotropy
Subtract Dipole Distortion At the level of δT ~ 10-5 : Observe complicated fluctuations
12 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB
Temperature Fluctuations - Isotropy and Homogeneity
Early Universe was highly homogenous
• 1989: COBE • Cosmic Microwave Background Explorer • Diffuse Infrared Background Experiment • DIRBE 0.001mm < l < 0.24mm • Far Infrared Absolute Spectrometer • FIRAS 0.1mm < l < 10mm • Differential Microwave Radiometer • DMR l= 3.3, 5.7, 9.6mm
COBE 13 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Temperature Fluctuations - The Dipole Anisotropy Like the Ether ? At the level of 10-3 : Observe Dipole Anisotropy One half of sky seemingly blue shifted to higher temperatures One half of sky seemingly red shifted to lower temperatures
Net motion of COBE wrt frame of reference in which CMB is isotropic
Doppler Effect? 1) increases energy of photons seen in direction of motion ~ 1+βcosθ Doppler Doppler Effect? 2) dν, interval of frequencies also increased ~ 1+βcosθ (β=v/c∼10−3) ZERO! Net Effect
1) Sweeps up cdt+vdtcosθ more photons in direction of travel ➠1+βcosθ 3 Iο (νο) = (1+βcosθ) Ie (νe) 2) Abberation effect (solid angle for moving observer decreases) ➠(1+βcosθ)−2
(1+ β cosθ) To(θ) = TCMB 1+ β
θ There is no quadrapole moment • COBE - Earth correction ~ 8 kms-1 1+ cos(θ ) • Earth - Sun correction ~ 30 kms-1 • Sun€ - Galactic Centre correction ~ 220 kms-1 • Galaxy - Local Group ~ 80 kms-1 ➽ -1 • Local Group moving towards Hydra at v~630±20kms ~ 0.002c 14 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Temperature Fluctuations • Early Universe was highly homogenous • Planck Time ~ quantum fluctuations • Inflation ~ amplified fluctuations ➠ macroscopic
• Fluctuations frozen until zdec • Fluctuations in the density (δρ/ρ)~3(δT/T)
δT T(θ,φ) − T (θ,φ) = T T
2 1/ 2 T (θ ,φ ) T2(θ2,φ2) δT 1 1 1 ≈1x10−5 T COBE,DMR ∞ l T1T2 = ∑ ∑almYlm (θ,φ), Temperature fluctuations defined of surface of sphere l= 0 m=−l € ➠ Expand as spherical harmonics 1/ 2 2 δT1 δT2 alm = = Cl (θ) T1 T2
Cl(θ) = Correlation function (mean product over all points seperated by θ) o Value of Cl(θ) as a function of θ (0< θ <180 ) gives a complete statistical description of the CMB 15 € 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB
Temperature Fluctuations ∞ l 1/ 2 2 δT1 δT2 T1T2 = ∑ ∑almYlm (θ,φ), alm = = Cl (θ) l= 0 m=−l T1 T2 Cl(θ) is scale dependent The value probed will depend on resolution of instrument
∞ Expand C ( ) in spherical harmonics€ 1 l θ C(θ) = (2l +1)C P cosθ (P = Legendre Polynomials) ∑ l l l 4π l= 0 o Individual Cl ’s probe structure on different angular scales given by θ=180 / l l = 0 the monopole l = 1 the dipole (due to our motion wrt CMB) € l = >1 fluctuations imprinted on SLS 1/ 2 l(l +1) ΔT = C 2π l
€
16 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Horizons and Fluctuations • Particle horizon: the distance light can have traveled from t = 0 to any given time t
• Event horizon: the distance light can travel from any given time t to t=∞ (or tmax). • Hubble Distance (Hubble Sphere): the distance beyond which recession velocity exceeds the speed of light.
c z dz r(z) = Comoving coordinate ∫0 Ro H(z) to dt r (t ) = c Past Light Cone lc e ∫te R(t) t dt r (t) = c Particle Horizon p ∫o R(t) ∞ dt r (t) = c Event Horizon E ∫t R(t)
c t dt DH = The Hubble Distance τ = H ∫0 R(t)
€ € Davis & Lineweaver 2003 17 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Horizons and Fluctuations: Large Scale Fluctuations θ>1o The Horizon Distance at recombination and decoupling (Surface of Last Scattering SLS)
tSLS cdt Horizon Distance given by particle horizon distance d = R(t )r (t) = R(t ) ~ 0.22Mpc H ,SLS SLS p SLS ∫o R(t) L d (t ) Angular Diameter Distance at SLS d = ( for z >>1) ≈ H o ~ 13Mpc A δθ z o For scales = Horizon scale at last scattering,€ L = d ⇒ δθ = θ ~ 1 H,SLS H o € o Scales of θ>1 different origin to scales θ<1 Spherical harmonics θ=180o / l θ>1o Corresponds to l<180 € observer o θ<1 Corresponds to l>180 horizon L/2 BIG θH INFLATION BANG dA horizon
observer Scales of θ>1o outside horizon ➠fluctuations from inflation ➠ Gravitational effect of primordial density fluctuations 18 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Horizons and Fluctuations: Sachs-Wolfe Effect
Scales of θ>1o outside horizon ➠fluctuations from inflation ➠ Gravitational effect of primordial density fluctuations
2 4πG Poisson eqn ∇ δΦ = 4πGδρ ≡ δε c 2
Fluctuations in density ➠ fluctuations in gravitational potential ➠ Gravitational Wells
At surface€ of last scattering: • Photon a local potential minima (bottom of well) has to climb out ➠ lose energy ➠ Redshift •Photon a local potential maxima (top of well) falls in ➠ gain energy ➠ Blueshift
δT 1 δΦ = SACHS - WOLFE EFFECT (1967) T 3 c 2
Red spots - higher temperature - potential maxima
€ Blue spots - lower temperature - potential minima 19 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Horizons and Fluctuations: Small Scale Fluctuations θ<1o
• Scales of θ<1o are inside the horizon ➠ baryons & photons • Baryons and photons fall into DM potential well
Compression At decoupling • Baryon/photon fluid in max compression ➠ high ρ,T Acoustic • Baryon/photon fluid in max expansion ➠ low ρ,T Oscillations Pressure
Expansion
horizon Fundamental
BIG INFLATION Overtones (l<180) BANG l = 180 Generally θ∼10 (l=180) corresponds to horizon potential wells in which Baryon/photon fluid had just reached max compression at time of decoupling (fundamental mode of oscillation).
These potential wells had sizes of ~ dH,SLS (seen as θH today) 20 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Horizons and Fluctuations Different angular scales probing different Physical processes
odd peaks even peaks max compression max rarefaction 1/2 ) fluctuations π (2 l the C 2 l in Power
600’ 60’ 6’ Dobbs 2003 Multipole (l) ⇒ ⇐ Angular scale (θ)
Savage 2003 21 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB CMB Experiments
Different angular scales probing different Physical processes.
http://planck.mpa-garching.mpg.de/Planck/experiments.html 22 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB CMB Experiments
1965 : CMB Discovery (Penzias & Wilson)
1977 : CMB Dipole Observed (Smoot et al)
1989 : CMB anisotropies observed (COBE)
2001 : Fundamental acoustic peak observed (Boomerang, Maxima)
2002 : Secondary acoustic peaks observed (Maxima,Boomerang DASI)
2002 : CMB Polarization (E-modes) observed (DASI)
2001 : Acoustic Peaks mapped (WMAP)
2005 ? : Discovery of B-modes ? (Polar Bear)
2007? : Characterize E-modes, Discovery of B-modes ? (Planck)
2015? : Discovery of B-modes ? (CMBPOL Einstein Probe Satellite) 23 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB WMAP
θ ~ 70 θ ~ 0.20
• Wilkinson Microwave Anisotropy Probe (2001 at L2) • Detailed full-sky map of the oldest light 380,000yr old in Universe. • It is a "baby picture" of the 380,000yr old Universe • Probe the CMB fluctuation Spectrum below the horizon scale • θ ~ 900 - 0.2 (l=2-1000)
24 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB WMAP
25 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Resolving the Different Cosmological World Models
Red - warm Blue - cool • Relative heights and locations of these peaks fundemental 1st harmonic ➡ signatures of properties of the gas at this time
Open Universe - photons move on faster diverging paths => angular scale is smaller for a given size
Peak moves to smaller angular scales (larger values of l)
****** THETHE UNIVERSEUNIVERSE ISIS FLATFLAT ****** 26 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Resolving the Different Cosmological World Models
Wandelt et al. 2004
27 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Polarization measurements CMB photons may be polarized
Stokes vector S=(I,Q,U,V) characterizies the intensity and polarization of light.
V=IRCP-ILCP Unpolarized light Q=U=V=0 polarized light, Q2+U2+V2=1 U=I+45-I-45 CMB Polarization V=0 Q=I0-I90
•Inflation ➠ Gravitational wave background DASI polarization measurement 2002 •CMB SLS gravity wave amplitude ➠ B (curl) mode component to CMB polarization •The smoking gun of inflation •Extend observations from 380,000yrs ➠ 10-35 s after Big Bang !! •Combination of Scalar, Vector & Tensor fields carry information on temperature anisotropies, acoustic peaks, cosmological parameter. •Information on epoch of re-ionization 28 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.3:2.3: ObservationsObservations ofof thethe CMBCMB Polarization measurements
~100mK Temperature E (Tensor)-modes ~4mK RMS
B (curl)-modes ≤300nK
1 degree B-mode amplitude is Determined only by the energy scale of inflation. Characterized by Tensor to scalar ratio ~ < 0.71 (WMAP Hu et al. astro-ph/0210096 29 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents
Backgrounds or Foregrounds? (signals or noise?)
The total integrated background light comes from many sources
• Cosmic Microwave Background Radiation CMBR 3K, peaks at 5cm
• Our Atmosphere: Sunlight scattered through atmosphere
• Zodiacal Light: Dust in plane of Solar System illuminated by Sun peaks at 60µm
• Galactic emission from dust, peaks at about 100µm
• Emission from hot gas, Synchrotron & free-free radio emission
• Extra galactic contributions from Radio Sources, Galaxies
• S-Z Compton scattering of CMBR photons by relativistic e- in cluster gas
30 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents Backgrounds or Foregrounds? (signals or noise?)
31 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents
Infrared Cirrus
• Extended whispy neutral interstellar dust in the Milky Way heated by the interstellar radiation field. • Cirrus emission peaks at far IR wavelengths (100µm) but was detected in all 4 IRAS bands • The galactic cirrus is a function of galactic latitude and is serious for wavelengths longer than 60µm.
P ∝ d 3 ∝ k 3
€
B100 Contours at 1 and 2 MJy/sr 32 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents Confusion to extragalactic sources
• Extragalactic Background • The superposition of sources below the flux limit / resolution of the instrument ∞ ∞ dN(Sν ) Iν = ∫ Sν dS ≡ ∑dSν dN(Sν ) 0 dS s
€
33 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents Contributions to the Extragalactic Background
Optical
34 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.4:2.4: BackgroundBackground LightLight ComponentsComponents Backgrounds or Foregrounds? (signals or noise?)
CMB Galactic HI (correlated) Galactic HI (uncorrelated) Galactic Synchrotron Extragalactic Radio Sources Extragalactic IR Sources Instrument on sky noise level
Bouchet 1999 35 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.5:2.5: SummarySummary Summary ❐ The CMB is strong vindication for the Hot Big Bang Theory
❐ The CMB • Isotropic to one part in 105 - An ideal Black Body • Shows a Dipole distortion due to the motion of the Earth wrt CMB frame • After Dipole Subtraction shows fluctuations on 30µK
❐ The epoch of recombination and decoupling define the Surface of Last Scattering (SLS) • The SLS is the last time the CMB interacated with matter • The SLS is a fossil of the 380,000yr old Universe • Primoridial density fluctuations are imprinted on the SLS
❐ The Fluctuations in the CMB has 2 origins • On scales > 1 degree ➠ Primordial Fluctuations from Inflation (Sachs Wolfe effect) • On scales < 1 degree ➠ acoustic oscillations in the baryon-photon plasma
❐ Decomposing the CMB fluctuations into spherical harmonics • Plot the fluctuation power as a function of angular size • Discriminate between different world models • WMAP - THE UNIVERSE IS FLAT !
❐ Foreground (contamination) • Zodiacal Light • Discriminate between different world models • Extragalactic Background (unresolved galaxies) • ***** One man’s noise is another man’s signal ***** BUT…. 36 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.5:2.5: SummarySummary Summary
37 04.2.26 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004 THE COSMIC BACKGROUND 2.5:2.5: SummarySummary Summary
ObservationalObservational CosmologyCosmology 2.2. TheThe CosmicCosmic BackgroundBackground 終終終
ObservationalObservational CosmologyCosmology 次：次：次： 3.3. StructureStructure FormationFormation
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