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)