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22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
1
THE COSMIC BACKGROUND
“My goal is simple. It is complete understanding of the universe, why it as it is and why it exists as all.”
— Stephen Hawking.
Observational Cosmology: 2.Observational Cosmology: 2.The Cosmic The Cosmic BackgroundBackground
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.1: The Isotropic Background2.1: The Isotropic BackgroundIs the Universe really homogeneous & isotropic ?? - Olbers Paradox revisited
Heinrich Olbers 1826 (Thomas Digges 1576)WHY IS THE SKY SO DARK ?The Sky should be the average surface brightness of a star !!!
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 =5cmAt a constant temperature of 2.73K
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.1: The Isotropic Background2.1: The Isotropic BackgroundIs the real Universe really homogeneous and isotropic ??
ActualTemperatureDistribution
1 / 1000 Temperaturevariation
1 / 100, 000 Temperaturevariation
4c m
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.1: The Isotropic Background2.1: The Isotropic BackgroundThe discovery of the microwave Background
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
• 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
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
HHH
H
Last Scattering
HH
HH
De-coupling
2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackgroundRecombination and Decoupling
zT
tR
• matter in thermal equilibrium with the radiation. photons and
electrons to interact via Thompson scattering
pe-
p pp
e-
e- e-
recombination•Temperature drops then p+e-H
recombination
• Eventually interactions stop allowing the photons to flow freely on scales of the horizon de-coupling
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• Era at which any photon last scattered off any electron
surface of last scattering
BIG BANG
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave 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
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackground
The Relic BackgroundEnergy density of radiation
€
ε =ρc2 = aT 4 ⇒ εγ ,o
= ρ oc2 = aTo
4 ≈ 0.26MeVm−3 ~ 5x10−5 ρ c
€
a = radiation constant = 4.73x10−3 MeVm−3K−4
€
εb,o = Ωb,oρ cc2 ⇒ 0.04 3Ho
2c 2
8πG
⎛ ⎝ ⎜
⎞ ⎠ ⎟= 0.04(5200MeVm−3) ≈ 208MeVm−3
Energy density of the matter
• Today : Energy density in Baryons is 800 times energy density in photons• But : Number density of Baryons to photon is 1 in 109
€
nγ ,o ≈εγ ,o
hυ 2mm
≈ 4x108 m−3Photon Number Density
€
nb,o ≈εb,o
mproton
= 0.22m−3Baryon Number density
€
η =nb,o
nγ ,o
≈ 0.224x108 ≈ 5.5x10−10
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackgroundThe Physics of Recombination
Temperature drops then p+e-H recombination depends on I. Ionization energy of Hydrogen =13.6eVII. The baryon/photon ratio, η~5x10-10
But even at lower temperatures sufficient photons with appropriate ionization energy
Number densities of particles as a function of To given by Boltzmann function
€
nH = gHmH kT2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟3 / 2
e−
m H c 2
kT
np = gp
mpkT2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟3 / 2
e−
m p c 2
kT
ne = gemekT2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟3 / 2
e−
me c 2
kT
⎫
⎬
⎪ ⎪ ⎪ ⎪
⎭
⎪ ⎪ ⎪ ⎪
nH
npne
= gH
gpge
mH
mpme
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
3 / 2kT
2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟−3 / 2
e−
(m H −m p −me )c 2
kT
Therefore define the fractional ionization
€
χ =np
np + nH
=np
nb
= ne
nb
np = number of unbound protons
nH = number of bound protonsnb = number of baryonsne = number of electrons
⎧
⎨ ⎪ ⎪
⎩ ⎪ ⎪
H binding energy = Q = (mp+me-mH)c2
mp~ mH
Statistical weights mp= me=2, mH=4SAHA EQUATION
€
nH
npne
= mekT2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟−3 / 2
eQkT
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackgroundThe Physics of Recombination
IonizationFraction
€
χ =np
np + nH
=np
nb
⇒nH = 1− χ
χnp
η =np
χnγ
⎧
⎨ ⎪ ⎪
⎩ ⎪ ⎪
1
2
€
nH
npne
= mekT2πh2
⎛ ⎝ ⎜
⎞ ⎠ ⎟−3 / 2
eQkTSaha
Equation 3
€
εBB (ν )dν = 16π 2hc 3
ν 3dνehν / kT −1
⇒ nγ = 2.404π 2
kThc ⎛ ⎝ ⎜
⎞ ⎠ ⎟3
Black Body Energy Density Distribution 4
€
1− χχ 2 = 3.84 kT
mec2
⎛ ⎝ ⎜
⎞ ⎠ ⎟−3 / 2
eQkT
Between temperatures of To~5000 2000, Ionization fraction drops 1 0
Quadratic in χ
24
31
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackgroundThe Physics of Recombination
DecouplingOptical Depth
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.2: The Origin of the Microwave 2.2: The Origin of the Microwave BackgroundBackgroundThe Physics of Recombination
Epoch of Recombination (kT~Q) To ~ 3740Kz ~ 1370, z ~ 200T ~ 240kyr, t ~ 70kyr
Epoch of Decoupling (~H) To ~ 3000z ~ 1089, z ~ 195T ~ 379,000yr, t ~ 118ky
10-26
10-24
10-22
10-20
10-18
10-16
10-14
10-12
10-10
10-8
10-6
0.0001
0.01
1
1250 2500 3750 5000 6250 7500
Fractional Ionization as function of Temperature
Ionization
Temperature (K)
χ(T)
χ(z)
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBTemperature Fluctuations
Observations of CMB Fluctuations in Temperature
At the level of T ~ 10-3 : Observe Dipole Anisotropy
Early Universe was highly homogenous
Subtract Dipole DistortionAt the level of T ~ 10-5 : Observe complicated fluctuations
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBTemperature 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
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBTemperature Fluctuations - The Dipole Anisotropy
At the level of 10-3 : Observe Dipole AnisotropyOne half of sky seemingly blue shifted to higher temperaturesOne half of sky seemingly red shifted to lower temperatures
Net motion of COBE wrt frame of reference in which CMB is isotropic
Like the Ether ?
1+ cos )
Doppler Effect? 1) increases energy of photons seen in direction of motion ~ 1+cosDoppler Effect? 2) d, interval of frequencies also increased ~ 1+cos =v/c Net D
oppler
Effect ZERO!
1) Sweeps up cdt+vdtcos more photons in direction of travel 1+cos 2) Abberation effect (solid angle for moving observer decreases) (1+cos
I () = (1+cos Ie (e)
€
To(θ) = TCMB(1+ β cosθ)
1+ β
• COBE - Earth correction ~ 8 kms-1
• Earth - Sun correction ~ 30 kms-1
• Sun - Galactic Centre correction ~ 220 kms-1
• Galaxy - Local Group ~ 80 kms-1
• Local Group moving towards Hydra at v~630±20kms-1 ~ 0.002c
There is no quadrapole moment
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBTemperature Fluctuations
• Early Universe was highly homogenous• Planck Time ~ quantum fluctuations• Inflation ~ amplified fluctuations macroscopic• Fluctuations frozen until zdec• Fluctuations in the density (ρρ)~3(TT)
€
TT
(θ,φ) =T(θ,φ) − T
T
δTT ⎛ ⎝ ⎜
⎞ ⎠ ⎟2
COBE ,DMR
1/ 2
≈1x10−5T1(1,1) T2(2,2)
€
T1T2 = almYlm (θ,φ)m=−l
l
∑l= 0
∞
∑ ,
alm2 1/ 2
= δT1
T1
δT2
T2
= Cl (θ)
Temperature fluctuations defined of surface of sphere Expand as spherical harmonics
Cl() = Correlation function (mean product over all points seperated by )Value of Cl() as a function of (0< <180o) gives a complete statistical description of the CMB
QuickTime™ and aSorenson Video decompressorare needed to see this picture.
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
€
T = l(l +1)2π
⎛ ⎝ ⎜
⎞ ⎠ ⎟
1/ 2
Cl
2.3: Observations of the CMB2.3: Observations of the CMBTemperature Fluctuations
€
T1T2 = almYlm (θ,φ)m=−l
l
∑l= 0
∞
∑ , alm2 1/ 2
= δT1
T1
δT2
T2
= Cl (θ)
Expand Cl() in spherical harmonics(Pl = Legendre Polynomials)
€
C(θ) = 14π
(2l +1)l= 0
∞
∑ ClPl cosθ
Cl() is scale dependent The value probed will depend on resolution of instrument
Individual Cl ’s probe structure on different angular scales given by =o / l l = 0 the monopolel = 1 the dipole (due to our motion wrt CMB)l = >1 fluctuations imprinted on SLS
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBHorizons 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.
€
r(z) = cRo
dzH(z)0
z∫ Comoving coordinate
rlc (te ) = c dtR(t)te
to∫ Past Light Cone
rp (t) = c dtR(t)o
t∫ Particle Horizon
rE (t) = c dtR(t)
Event Horizont
∞∫
DH = cH
The Hubble Distance
€
τ = dtR(t)0
t∫
Davis & Lineweaver 2003
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
BIGBANG INFLATION
2.3: Observations of the CMB2.3: Observations of the CMBHorizons and Fluctuations: Large Scale Fluctuations o
dA
L/2H
horizon
horizon
observer
observer
The Horizon Distance at recombination and decoupling (Surface of Last Scattering SLS)
€
dH ,SLS = R(tSLS )rp (t) = R(tSLS ) cdtR(t)o
tSLS∫ ~ 0.22MpcHorizon Distance given by particle horizon distance
Angular Diameter Distance at SLS
€
dA = Lδθ
( for z >>1) ≈ dH (to)z
~ 13Mpc
For scales = Horizon scale at last scattering,
€
L = dH,SLS⇒ δθ = θ H ~ 1o
Scales of o different origin to scales o
Spherical harmonics =o / lo Corresponds to l<180o Corresponds to l>180
Scales of o outside horizon fluctuations from inflation Gravitational effect of primordial density fluctuations
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBHorizons and Fluctuations: Sachs-Wolfe Effect
Scales of o outside horizon fluctuations from inflation Gravitational effect of primordial density fluctuations
€
∇2δΦ = 4πGδρ ≡ 4πGc 2 δε
Fluctuations in density fluctuations in gravitational potential Gravitational Wells
Poisson eqn
At surface of last scattering:
Red spots - higher temperature - potential maxima
Blue spots - lower temperature - potential minima
• 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
€
TT
= 13
δΦc 2
SACHS - WOLFE EFFECT (1967)
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
BIGBANG INFLATION
2.3: Observations of the CMB2.3: Observations of the CMBHorizons and Fluctuations: Small Scale Fluctuations o
horizon
horizon
• Scales of o are inside the horizon baryons & photons• Baryons and photons fall into DM potential well
Generally (l=180) corresponds to potential wells in which Baryon/photon fluid had just reached max compression at time of decoupling (fundamental mode of oscillation).
Compression
Pressure
Expansion
AcousticOscillations
Overtones (l<180)
Fundamental
l = 180
At decoupling• Baryon/photon fluid in max compression high ρ,T• Baryon/photon fluid in max expansion low ρ,T
These potential wells had sizes of ~ dH,SLS (seen as H today)
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBHorizons and Fluctuations
Multipole (l) Angular scale ()
60’
6’
600’
Pow
er in
the
fluct
uatio
nsl2 C
l(2)
1/2
Savage 2003
Different angular scales probing different Physical processes
odd peaks max compression
even peaksmax rarefaction
Dobbs 2003
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBCMB Experiments
Different angular scales probing different Physical processes.
http://planck.mpa-garching.mpg.de/Planck/experiments.html
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBCMB 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)
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBWMAP
QuickTime¢‚∞˙ Sorenson Video æ–√‡ «ÿ¡¶±‚∞°
¿Ã ±◊∏≤¿ª ∫∏±‚ ¿ß«ÿ « ø‰«’¥œ¥Ÿ.
• 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• ~ 900 - 0.2 (l=2-1000)
~ 70 ~ 0.20
QuickTime™ and aSorenson Video decompressorare needed to see this picture.
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBWMAP
QuickTime¢‚∞˙ Sorenson Video æ–√‡ «ÿ¡¶±‚∞°
¿Ã ±◊∏≤¿ª ∫∏±‚ ¿ß«ÿ « ø‰«’¥œ¥Ÿ.
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
Red - warm Blue - cool
2.3: Observations of the CMB2.3: Observations of the CMBResolving the Different Cosmological World Models
fundemental 1st harmonic• Relative heights and locations of these peaks 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)
*** THE UNIVERSE IS FLAT ***
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBResolving the Different Cosmological World Models
Wandelt et al. 2004
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMBPolarization measurements
•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
DASI polarization measurement 2002
Stokes vector S=(I,Q,U,V) characterizies Stokes vector S=(I,Q,U,V) characterizies the intensity and polarization of light.the intensity and polarization of light.
Q=IQ=I00-I-I9090
U=IU=I+45+45-I-I-45-45
V=IRCP-ILCP Unpolarized light Q=U=V=0Unpolarized light Q=U=V=0polarized light, Qpolarized light, Q22+U+U22+V+V22=1=1CMB Polarization V=0CMB Polarization V=0
CMB photons may be polarizedCMB photons may be polarized
•Inflation Gravitational wave background
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.3: Observations of the CMB2.3: Observations of the CMB
Hu et al. astro-ph/0210096
~100mK
~4mK RMS
≤300nK
1 degree
TemperatureE (Tensor)-modes
B (curl)-modes
B-mode amplitude is Determined only by the energy scale of inflation. Characterized by Tensor to scalar ratio ~ < 0.71 (WMAP
Polarization measurements
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponents
Backgrounds or Foregrounds? (signals or noise?)
• 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
60m• Galactic emission from dust, peaks at about 100m• 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
The total integrated background light comes from many sources
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponentsBackgrounds or Foregrounds? (signals or noise?)
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponents
Infrared Cirrus
B100 Contours at 1 and 2 MJy/sr
• 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 ∝ d3 ∝ k 3
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponentsConfusion to extragalactic sources
• Extragalactic Background• The superposition of sources below the flux limit / resolution of the instrument
€
Iν = Sν0
∞
∫ dN(Sν )dS
dS ≡ dSν dN(s
∞
∑ Sν )
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponentsContributions to the Extragalactic Background
Optical
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND2.4: Background Light 2.4: Background Light ComponentsComponentsBackgrounds or Foregrounds? (signals or noise?)
CMBGalactic HI (correlated)Galactic HI (uncorrelated)Galactic SynchrotronExtragalactic Radio SourcesExtragalactic IR Sources
Instrument on sky noise level
Bouchet 1999
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.5: Summary2.5: SummarySummary
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 30K
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….
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.5: Summary2.5: SummarySummary
22/04/23 Chris Pearson : Observational Cosmology 2: The Cosmic Background - ISAS -2004
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THE COSMIC BACKGROUND
2.5: Summary2.5: SummarySummary
Observational Cosmology Observational Cosmology 2. The Cosmic Background2. The Cosmic Background 終終
次:次:Observational Cosmology Observational Cosmology
3. Structure Formation3. Structure Formation