The Cosmic Microwave Background Radiation
– Introduction and experimental techniques/challenges– Science and future experiments
Dorothea Samtleben, ESTRELA Workshop,Bonn, April 2008
Development of one mode
Animation by Wayne Hu, http://background.uchicago.edu/~whu/
Description of anisotropies
Statistical properties of CMB predictable Representation by spherical harmonics Ylm
T θ ,ϕ =∑ alm Y lmθ ,ϕ Temperature:
C l =< alm alm* ¿
¿
TΔ 2=l l1
2 πCl
Definition for coefficients:
Variance (observable):
WMAP Temperature power spectrum
Initial conditions
Accoustic oscillations
Horizon scale at last scatteringand curvature determine position of first peak
Different Polarization patterns
Density fluctuations Emodes
Gravity waves E and Bmodes, amplitude determined by energy scale of inflation (often linked to GUT scale)
Division of Polarization into gradient (Emode) and curl component (Bmode)
Gravitational lensing Emodes appear as Bmodes
Different Polarization patterns
Density fluctuations Emodes
Gravity waves E and Bmodes, amplitude determined by energy scale of inflation (often linked to GUT scale)
Division of Polarization into gradient (Emode) and curl component (Bmode)
EMode(gradient component)
BMode(curl component)
Gravitational lensing Emodes appear as Bmodes
Polarization Power spectra expectation
Polarization spectra
Most parameters already well measured from TT.
EE spectrum is a fundamental check on our understanding
EE is also sensitive to nonstandardmodel effects (eg. isocurvature)
TT
Lambda w
ebsite, WM
AP
pictures
EE(From MCMC)K. Vanderlinde
BB can tell us a lot of new things (eg. energy scale of inflation, neutrino mass)
BB Power Spectrum Uncertainty(from MCMC, K. Vanderlinde)
BB still very uncertain.(Even if our model is correct & complete.)
Tensors
Lensing
EE Power Spectrum Measurements
EE Power Spectrum Measurements
So far, EE spectrum is consistent with standard
ΛCDM model.
EE Power Spectrum Measurements
So far, EE spectrum is consistent with standard
ΛCDM model.
But it’s also consistent with a lot of others.
CAPMAP Results
EE spectrum BB limits (95%)
• New EE measurements at small angular scales
• One of the best limits for BB
Simulated CMB sky with T/S=0
Simulated CMB sky with T/S=0.2(best upper limit by WMAP+external data)
Cosmological parameters
11 basic parameters:
A S(T) Amplitude of primordial scalar (tensor) spectrum
r=T/S Ratio of tensor to scalar fluctuations
ns(T) Tilt of scalar (tensor) spectrum
ωb =Ωb h2 Baryon density
ωm =Ωm h2 Matter density
ωΛ =ΩΛh2 Dark energy density
Ωk Curvature, Ωm+ΩΛ+ Ωk = 1H0 Hubble constant
w Dark Energy equation of state
Cosmological parameter estimation from CMB measurements
Animation by M. Tegmark
Temperature Anisotropies(WMAP+others)
TemperaturePolarizationCorrelation (WMAP)
Galaxy survey (SDDS)
Cosmological parameter estimation from CMB measurements
Animation by M. Tegmark
Temperature Anisotropies(WMAP+others)
TemperaturePolarizationCorrelation (WMAP)
Galaxy survey (SDDS)
CMB confirms ΛCDM
Shape of power spectra determined by content and development of the Universe
=> Extract information on cosmological parameters
Baryon Content consistent with BBN results Dark Energy consistent with Supernovae results Hubble constant consistent with HST results Age of the Universe consistent with globular clusters results
CMB power spectrum consistent with inflationary predictions of flatness and gaussian adiabatic scaleinvariant fluctuations
CMB confirms ΛCDM
WMAP CMB also consistent with NO dark energy but Hubble constant would have to be 30 km/s/Mpc!
Degeneracies don‘t allow a completely autonomous determination of all parameters
CMB data complementary to other cosmological observations
WMAP 3year publications
Curvature degenerate with dark energy contentOther cosmological probes solve degeneracyAssuming Dark Energy with constant w=1
Curvature Komatsu et al.WMAP 5year results
constant w=1 assumed
w allowed to be different from 1
Tensortoscalar ratio r=T/S
Gravitational waves create tensor contributionSize of signal parametrized by T/S
Spectral tilt nS
1−ns=M Pl2 [3V '
V 2
−2 V ''V
2]Tilt of spectrum contains information about slope/curvature of inflation potential
nS 0 .986±0 . 02 0 .968±0 . 015 1. 087−0 . 0730 . 072
r < 0 . 43 < 0 .2 < 0 .58dnS /d ln k − − −0 .050±0 .034
WMAPWMAP+BAO+SN
WMAP
Inflationary models
r=831−nS
16 M Pl2
3V ''V
Singlefield modelsRelation between T/S=r and ns
and inflationary potential V(Φ)
Small r hard to measure,so far constraints mainlyfor positive curvature models (V‘‘>0)
Contours show WMAP+BAO+SN,(no running index)
Neutrino mass
∑ mυ1.31.5 eV
∑ mυ0 .610 .66 eV
for w=−1≠−1 Including BAO+SN
CMB science of the future
• Polarization break parameter degeneracies primordial gravity waves neutrino mass/dark energy parameters from lensing cosmic strings primordial magnetic fields …
• Temperature high l inflationary physics cluster physics/dark energy from Sunyaev Zel‘dovich effect …
Challenges of the future
• High sensitivity receivers operate close to fundamental limits => large receiver arrays
• Exquisite foreground removal little is known about microwave (polarization) foregrounds => multiple frequencies for removal required => specific foreground studies crucial• Unprecedented control of systematics => instrumental and environmental effects have to be minimized and well controlled
High precision measurements of temperature and polarization power spectra
V 1/4 = 3.3 * 1016 (T/S)1/4 GeVUNIQUE ACCESS TO POSSIBLY NEWPHYSICS AT PLANCK SCALE!
T/S related to energy scale of inflation:
Rewards of the Bmodes
Future Experiments
South Pole Telescope, 10m
> 1000 receivers
Significant increase of sensitivity only achievable with multiple receivers => Arrays mit 10 – 1000 receivers at one telescope!
QUAD (South Pole)Running! 31 pixels, 2 frequencies
APEX SZ330 pixels
Future direction
Bolometer arrays
Polarization sensitive bolometers were successfully used for CMB Polarization measurements by Boomerang, will also be used by Planck HFI
Transition Edge Sensitive (TES)Bolometers allow multiplexed SQUID readout and easy mass production (photolithography)
Adrian Lee, Berkeley
APEX SZ, TES Bolometer Array (330 Pixels)
Antenna coupled TES bolometerswill enable easily scalable arrayswithout feedhorns(Spider, Polarbear)
3 cm
5 mm
New approach: Interferometric Bolometry
BRAIN pathfinder at Dome C 2x256 elements planned at 90 and 150 GHz
Rome, Milano, Cardiff, APC Paris,CESR Toulouse, CSNSM Orsay, IAS Orsay
MBI prototype in lab, going to Pine Bluff Observatory 64 elements planned at 90 GHz
Brown, Cardiff, LLNL, Northwestern,UC San Diego, Richmond, Wisconsin
Combine the benefits of interferometers with the sensitivity of bolometers: Principle of adding interferometer: Measure (A+B)² and (AB)² => difference gives correlation AB
Future groundbased/balloon CMB experiments
• Bolometric arrays ACT, APEX, BICEP, ClOVER, EBEX, OLIMPO, PAPPA, Polarbear, QUAD, Spider, SPT
• Pseudocorrelation receivers QUIEt, BarSport
• Interferometers AMI, AMIBA, SZA, VSA
• Bolometric interferometers MBI, BRAIN
Already taking dataFunded and under developmentFunding pendingItalics: SZ
Future groundbased/balloon CMB experiments
• Bolometric arrays ACT, APEX, BICEP, ClOVER, EBEX, OLIMPO, PAPPA, Polarbear, QUAD, Spider, SPT
• Pseudocorrelation receiver QUIEt, BarSport
• Interferometers AMI, AMIBA, SZA, VSA
• Bolometric interferometers MBI, BRAIN
Atacama Desert ChileSouth Pole/Dome CBalloon
CBI site at Atacama Desert, 5000 m altitude
QUAD at South Pole
Low Frequency Instrument (LFI) High Frequency
Instrument (HFI)
Launch end of 2008
Multifrequency coverage in one instrument
PseudoCorrelation receivers for low frequencies 30, 44, 70 GHz Bolometric receivers at high frequencies 100, 143, 217, 353 GHz
Spacebased: Planck
Future CMB experiments(no interferometers)
Beware: sqrt(2)s …Plotted: NEQ with NET=NEQ (Q=(TxTy)/2)
These are goals/current plans BUT: some experiments are not yet (completely) fundedand future technologies are not yet fully established, don‘t take the numbers too literally!Also: SYSTEMATICS/FOREGROUNDS not taken into account in these numbers
Very few low frequency experimentsunderway!
*: BalloonX :Fundingpending
x
SZSZ
SZ
SZ
Future CMB experiments(no interferometers)
These are goals/current plans BUT: some experiments are not yet (completely) fundedand future technologies are not yet fully established, don‘t take the numbers too literally!Also: SYSTEMATICS/FOREGROUNDS not taken into account in these numbers
Reach at the temperature power spectrum
Estimates for Planck and ACTDe OliveiraCosta
WMAP
Planck
Statistical uncertainties only! Results will differ!
Q/U Imaging ExperimenT Collaboration
Miami
Chicago (KICP)
ColumbiaPrinceton
ManchesterOxford Oslo MPIfRBonn
KEK
Atacama Observational Site Chile (CBI site)
5 countries, 12 institutes, ~30 people5 countries, 12 institutes, ~30 people
CaltechJPL
Stanford(KIPAC)
CAPMAPObservational Site
Q/U Imaging ExperimenT (QUIET)
International Collaboration by: Caltech (Readhead), Chicago (Winstein), Columbia (Miller), JPL (Gaier), Manchester (Piccirillo), Miami (Gundersen), MPIfR Bonn (DS), Oslo (Eriksen), Oxford (Jones), Princeton (Staggs)
~1 inch
Radiometer on a chip:
• Automated assembly and optimization
• Large array of correlation polarimeters
Only groundbased effort using coherent detectors
Measuring Q/U simultaneously in each pixel
Complementing frequencies from other experiments
Produced by JPL (based on developments for Planck LFI), Todd Gaier
Plans for QUIET
Horn array
Ortho Mode Transducers
Modules, in dewar electronics
Cryostat
Window
Phase I,in Chile 2008
Phase II2009++
Observations at large and small scales! (resolution 14‘/5‘ for 90 GHz)
• Install up to four new 1.4m telescopes on CBI platform in the Atacama Desert (5000m altitude)
• Move 7m telescope to Chile
91 W band elements19 Q band elements
> 500 elements
7m telescope at Crawford Hill, NJ CBI platform, Atacama Desert, Chile
U
Ex
Eb
Ey
Ea
QUIET L/R Correlator:Simultaneous Q/U measurements
Q
4kHz phase switching
Radiometer on a chip
Det. Diode
L=EX+iEY R=EX−iEY
HEMT Amp.
Phaseswitch4kHz
180° Coupler
90° Coupler
|L±R|2+Q −Q
−U|L±iR|2+U
+1 ±1
WBand (90 GHz)
Prototype arrays
QBand (44 GHz)
~2 inch~1 inch
Differential total power receiver
Ex1 (Ey2) Ey2(Ex1)
⇒ Demodulated output:
Ex12 – Ey22 = Tx1 – Ty2
Ex1+Ey2 Ex1 –Ey2
Phase switch +()
Ex12 Ey22 Ex22 – Ey12
Tx1 – Ty2 Tx2 – Ty1
Differential total power receivers
Qband Wband
10% of the arrays populated with differential total power receivers
Measuring ∆T between neighboured beams, phase switching reduces 1/f of amplifiers
Identification/characterization of unpolarized foregrounds CMB TT and TE measurements
Horn array and cryostat
Horn array made from 100 single platelets which are bound together by diffusion bonding
Return loss measurement
Backend with digital demodulation
• Sampling at 800 kHz• Monitors highfrequency noise• 4kHz switching, digital blanking and demodulation by means of an FPGA• Quadrature (null demodulation) data set produced
Diode differencing removes drifts
Lab measurements
• Reflection by metal plate– Known polarization, ~100 mK
• Direct measures of– Responsivity– Noise level
Cryogenicbucket
Metal plate(reflector)
Receiver
~1KRMS~50mK(@100Hz)
θ
sin2θ
Telescope / Optics
• 1.4m primary mirror• Resolution in FWHM:
– 13 arcmin (Wband)– 28 arcmin (Qband)
• Inherit CBI mountPrimary Mirror
2nd Mirror
Mount
Focal Plane(Receiver)
ElectronicsBox
PlateletArray
Mirrors & Support Structure~40cm
CBI mount
Observation regions
Map precision on1x1 degree pixel:
Planck: 1 µK (100 GHz) QUIET: 101 µK (90 GHz)
Kband (23 GHz) WMAP 5 years, polarization intensity
Preliminary choice of 4x400 square degree patches:
low foreground regions (overlap with Quad/EBEX/Polarbear planned)
elevation above 40 degrees
distribution to allow continuous scanning
CAPMAP fieldCAPMAP field
PseudoCl Simulation
TODRecon. Map
CMB power
PseudoCl
• Fast• EBmix
CMB signal
Detector noise
Scanning
Methodology from Hivon et. al. (2001)
Naïve TOD filter• Fast• 1/f suppression• Possible syst.
• EBmix• l l ’ coupling
Expected resultsfor phase I (phase II)
50 (500) Wband receivers with ~340 µK sqrt(s) per element10 (20) months observing with 50% efficiency reaching r~102 in phase II
EE spectrum BB spectrum (r=0.2)