Latest Results from W Latest Results from W
MAP: Three-year Obser MAP: Three-year Obser
vations vations
Eiichiro Komatsu (UT Austin) Eiichiro Komatsu (UT Austin)
Texas Symposium in Melbourne Texas Symposium in Melbourne
December 15, 2006 December 15, 2006
Full Sky Microwave Map Full Sky Microwave Map
Penzias & Wilson, 1965
Uniform, “Fossil” Light from the Big Bang
-Isotropic -Unpolarized
Galactic Center Galactic Anti-
center
A. Penzias & R. Wilson, 1965 A. Penzias & R. Wilson, 1965
CMB
T = 2.73 K Helium Supe
rfluidity
T = 2.17 K
COBE/FIRAS, 1990 COBE/FIRAS, 1990
Perfect blackbody = Thermal equilibrium = Big Bang
COBE/DMR, 1992 COBE/DMR, 1992
Gravity is STRONGER in cold spots: T/T~
Isotropic?
COBE, “Followed-up” by WMAP COBE, “Followed-up” by WMAP
COBE
WMAP
COBE 1989
WMAP 2001
[COBE’s] measurements als o marked the inception of co smology as a precise science . It was not long before it was followed up, for instanc e by the WMAP satellite, whi ch yielded even clearer imag es of the background radiati on.
Press Release from the Nobel Foundatio n
So, It’s Been Three Years Since So, It’s Been Three Years Since
The First Data Release in 2003.
The First Data Release in 2003.
What Is New Now?
What Is New Now?
POLARIZATION DATA!!
POLARIZATION DATA!!
CMB is not only anisotropic, but CMB is not only anisotropic, but
also
also polarizedpolarized..
The Wilkinson Microwave The Wilkinson Microwave
Anisotropy Probe Anisotropy Probe
• A microwave satellite working at L2
• Five frequency bands
– K (22GHz), Ka (33GHz), Q (41GHz), V (61GHz), W (94GHz) – Multi-frequency is crucial for cleaning the Galactic emission
• The Key Feature: Differential Measurement
– The technique inherited from COBE – 10 “Differencing Assemblies” (DAs)
– K1, Ka1, Q1, Q2, V1, V2, W1, W2, W3, & W4, each consisting of two radiometers that are sensitive to orthogonal linear polarization modes.
• Temperature anisotropy is measured by single difference.
• Polarization anisotropy is measured by double difference.
POLARIZATION DATA!!
WMAP Three Year Papers WMAP Three Year Papers
K band (22GHz) K band (22GHz)
Ka Band (33GHz) Ka Band (33GHz)
Q Band (41GHz) Q Band (41GHz)
V Band (61GHz) V Band (61GHz)
W Band (94GHz) W Band (94GHz)
The Angular Power Spectrum The Angular Power Spectrum
• CMB temperature anisotropy is very clos e to Gaussian (Komatsu et al., 2003); t hus, its spherical harmonic transform, alm, is also Gaussian.
• Since alm is Gaussian, the power spectru m:
completely specifies statistical proper ties of CMB.
WMAP 3-yr Power Spectrum WMAP 3-yr Power Spectrum
What Temperature Tells Us What Temperature Tells Us
Distance to z~1100
Baryon- to-Photon Ratio
Matter-Radiation Equality Epoch Dark Energy/
New Physics?
nnss: Tilting Spectrum: Tilting Spectrum
nnss>1: “Blue Spectru>1: “Blue Spectru m”m”
nnss: Tilting Spectrum: Tilting Spectrum
nnss<1: “Red Spectrum<1: “Red Spectrum
””
CMB to Cosmology CMB to Cosmology
&Third
Baryon/Photon Density Ratio
Low Multipoles (ISW)
Constraints on Inflation Models
K Band (23 GHz) K Band (23 GHz)
Dominated by synchrotron; Note that polarization direction is perpendicular to the magnetic field lines.
Ka Band (33 GHz) Ka Band (33 GHz)
Synchrotron decreases as -3.2 from K to Ka band.
Q Band (41 GHz) Q Band (41 GHz)
We still see significant polarized synchrotron in Q.
V Band (61 GHz) V Band (61 GHz)
The polarized foreground emission is also smallest in V band.
We can also see that noise is larger on the ecliptic plane.
W Band (94 GHz) W Band (94 GHz)
While synchrotron is the smallest in W, polarized dust (hard to see by eyes) may contaminate in W band more than in V band.
Polarization Mask Polarization Mask
fsky=0.743
Jargon: E-mode and B-mode Jargon: E-mode and B-mode
• Polarization has directions!
• One can decompose it into a divergence -like “E-mode” and a vorticity-like
“B-mode”.
E-mode B-mode
Seljak & Zaldarriaga (1997); Kamionkowski, Kosowsky, Stebbins (1997)
Polarized Light Filtered
Polarized Light Un-filtered
Physics of CMB Polarization Physics of CMB Polarization
• Thomson scattering generates polarization, if and only if…
– Temperature quadrupole exists around an electron – Where does quadrupole come from?
• Quadrupole is generated by shear viscosity of photon-baryon fluid.
electron isotropic
anisotropic
no net polarization
net polarization
Boltzmann Equation Boltzmann Equation
• Temperature anisotropy, , can be generated by gravi tational effect (noted as “SW” = Sachs-Wolfe, 1967)
• Linear polarization (Q & U) is generated only by scat tering (noted as “C” = Compton scattering).
• Circular polarization (V) is not generated by Thomson scattering.
Primordial Gravity Waves Primordial Gravity Waves
• Gravity waves also create quadrupolar temperature anisotropy -> Polarization
• Most importantly, GW creates B mode.
Power Spectrum Power Spectrum
Scalar T
Tensor T
Scalar E Tensor E
Tensor B
Polarization From Reionizati Polarization From Reionizati
onon
• CMB was emitted at z~1100.
• Some fraction of CMB was re-scattered in a reion ized universe.
• The reionization redshift of ~11 would correspon d to 365 million years after the Big-Bang.
z=1100, ~ 1
z ~ 11, ~ 0.1
First-star formation
z=0 IONIZED
REIONIZED NEUTRAL
e-
e- e- e-
e-
e- e-
e- e-
e-
e- e-
e- e- e-
Measuring Optical Depth Measuring Optical Depth
• Since polarization is generated by scattering, the amplitude is given by the number of scattering, or optical depth of Thomson scattering:
which is related to the electron column number density as
Temperature Damping, and Temperature Damping, and
Polarization Generation Polarization Generation
“Reionization Bump”
2
e-
• Outside P06
– EE (solid) – BB (dashed)
• Black lines
– Theory EE
• tau=0.09
– Theory BB
• r=0.3
• Frequency = Geometri c mean of two freque ncies used to comput e Cl
Masking Is Not Enough:
Masking Is Not Enough:
Foreground Must Be Cleaned Foreground Must Be Cleaned
Rough fit to BB FG in 60GHz
Clean FG Clean FG
•Only two-parameter fit!
•Dramatic improvement in chi-squared.
•The cleaned Q and V maps have the reduced chi-squared of ~1.02 per DOF=4534 (outside P06)
BB consistent with zero after FG removal.
3-sigma detection of EE.
The “Gold” mu ltipoles: l=3,4, 5,6.
Parameter Determination (M Parameter Determination (M
L): L):
First Year vs Three Years First Year vs Three Years
• The simplest LCDM model fits the data very well.
– A power-law primordial power spectrum – Three relativistic neutrino species
– Flat universe with cosmological constant
• The maximum likelihood values very consistent
– Matter density and sigma8 went down slightly
Parameter Determination (Mea Parameter Determination (Mea
n): n):
First Year vs Three Years First Year vs Three Years
• ML and Mean agree better for the 3yr data.
– Degeneracy broken!
Low-l TE Data: Comparison betwe Low-l TE Data: Comparison betwe
en 1-yr and 3-yr en 1-yr and 3-yr
• 1-yr TE and 3-yr TE have about the same error-bars.
– 1yr used KaQVW and wh ite noise model
• Errors significantly underestimated.
• Potentially incomple te FG subtraction.
– 3yr used QV and corre lated noise model
• Only 2-sigma detecti on of low-l TE.
High-l TE Data High-l TE Data
• The amplitude and phases of high-l TE data agree very we ll with the prediction from TT data and linear perturbat ion theory and adiabatic initial conditions. (Left Pane l: Blue=1yr, Black=3yr)
Phase Shift
Amplitude
High-l EE Data High-l EE Data
• When QVW are coadded, the high-l EE amplitude relative t o the prediction from the best-fit cosmology is 0.95 +- 0.35.
• Expect ~4-5sigma detection from 6-yr data.
WMAP: QVW combined
1st year vs 3rd year1st year vs 3rd year
• Tau is almost entirely determined by the EE fr om the 3-yr data.
– TE adds very little.
• Dotted: Kogut et al.’s stand-alone tau analysi s from TE
• Grey lines: 1-yr full a nalysis (Spergel et al.
2003)
Tau is Constrained by EE Tau is Constrained by EE
• The stand-alone analysis of EE data gives
– tau = 0.100 +- 0.029
• The stand-alone analysis of TE+EE gives
– tau = 0.092 +- 0.029
• The full 6-parameter analysis gives
– tau = 0.088 +- 0.029 (Spergel et al.; no SZ)
• This indicates that the stand-alone EE analysis has exhausted most of the information on tau contained in the polarization data.
– This is a very powerful statement: this immediately implie s that the 3-yr polarization data essentially fixes tau in dependent of the other parameters, and thus can break mass ive degeneracies between tau and the other parameters.
Degeneracy Finally Broken:
Degeneracy Finally Broken:
Negative Tilt & Low Fluctuation Negative Tilt & Low Fluctuation
Amplitude Amplitude
Degeneracy Line from Temperature Data Alone
Polarization Data Nailed Tau
Temperature Data Constrain “8exp(-)”
Lower
Polarization Nailed Tau
Lower 3rd peak
Constraints on GW Constraints on GW
• Our ability to constrain the
amplitude of gravity waves is still coming mostly from the
temperature spectrum.
– r<0.55 (95%)
• The B-mode
spectrum adds very little.
• WMAP would have to integrate for at least 15 years to detect the B-mode spectrum from
inflation.
What Should WMAP Say What Should WMAP Say
About Inflation Models?
About Inflation Models?
Hint for ns<1 Zero GW
The 1-d
marginalized constraint from WMAP alone is ns=0.96+-0.02.
GW>0
The 2-d joint constraint still allows for ns=1.
What Should WMAP Say What Should WMAP Say
About Flatness?
About Flatness?
Flatness, or very low Hubble’s
constant?
If H=30km/s/Mpc, a closed universe
with Omega=1.3 w/o cosmological constant still fits the WMAP data.
What Should WMAP Say What Should WMAP Say
About Dark Energy?
About Dark Energy?
Not much!
The CMB data alone cannot constrain w very well.
Combining the large-scale
structure data or supernova data breaks degeneracy
between w and matter density.
What Should WMAP Say What Should WMAP Say
About Neutrino Mass?
About Neutrino Mass?
3.04 )
• Understanding of
– Noise,
– Systematics, – Foreground, and
• Analysis techniques
• have significantly impro ved from the first-year release.
• A simple LCDM model fits both the temperature and polarization data very w
• To-do list for the next data release (now working on the 5-year data)ell.
• Understand FG and noise better.
• We are still using only 1/2 of the polarization data.
• These improvements, combined with more years of data, would further reduce the error on tau.
• Full 3-yr would give delta(tau)~0.02
• Full 6-yr would give delta(tau)~0.014 (hopefully)
• This will give us a better estimate of the tilt, and better constraints on inflation.
Summary Summary
•Tau=0.09+-0.03