2-year Total Intensity Observations 2000+2001

1-year Polarization Observations 2003+2004

Cosmic Background Imager

Tony ReadheadZeldovich celebration

Moscow December 2004

Caltech:(Cartwright*)Dickinson(Keeney)(Mason)(Padin (project scientist))PearsonReadhead(Schaal)(Shepherd)(Sievers*)(Udomprasert*)(Yamasaki)

CITA:BondContaldi(Pen)Pogosyan(Prunet)

Chicago:CarlstromKovac*LeitchPryke

U. de Chile:Achermann*(Altamirano)BronfmanCasassusMayOyarce

Berkeley:(Halverson*)(Holzapfel)

NRAO:Myers

MSFC:(Joy)

* students altitude 16,800 feet

U. de ConcepcionBustos*Reeves*Torres

Polarization Observations

Pablo Altamirano, Ricardo Bustos, John Kovac

Rodrigo Reeves, Cristobal Achermann

CBI, 5080 m

APEX

1 meter

CBI Configuration for Polarization Observations

Very close to a perfect matched filter to the expected polarization signal

LCP

RCP

v

u

D cos D si

n

u.x

D=uE1(t) E2(t)

/2

complex correlator

Im Re

to c

eles

tial s

igna

l

cmb temperature variations T(x)

V(u)

_ie

e2iu x.

Q U

Thomson scattering gives rise to E-mode (curl-free) polarization (~10 % of T)

Gravitational waves and lensing also give rise to B-mode polarization (<1 % of T)

North

-Q

-U

CBI:78 baselines

10 frequency channels= 780 separateinterferometers

CBI Flux Density scale is tied to the WMAP Flux Density scale, absolute uncertainty = 1.3%

Page et al. ApJ 2003, 148, 39

Silk damping

CBI Polarization EE Observations

strategy: size of mosaics chosen so that at the end of 3-4 years the cosmic variance will equal the thermal noise in the center of the CBI l-range

If point sources were a factor we would see a l(l +1)x Cl dependence in both EE and BB

simulations with realistic point source contributions show that the first two

bins are expected to change by < 4 K2

significance of shaped fit is 8.9- without point source projection, or 7.0- with point source projection

2.1-3.4-

1.6-

CBI EE Polarization Phase

• Parameterization 1: envelope plus shiftable sinusoid– fit to “WMAP+ext” fiducial spectrum using

rational functions

( )( ) ( ) ( )[ ]φ++

=+lll

ll l

kgfa

C EE

sin

1

slice at: slice at: aa=1=1

== 2525°±°±3333°° rel. phase rel. phase

7.0- to 8.9- detection in amplitude of EE-mode polarizationand 3- rejection of “in phase” EE-TT spectra

Example: Acoustic Overtone Pattern

• Sound crossing angular size at photon decoupling

• Overtone pattern– TT extrema spaced at j intervals– EE spaced at j+1/2 (plus corrections)

( )21+∝

∝

j

j

sEEj

sTTj

ll

ll

π

π

1−≈ slθ

CBI EE Polarization Phase

• Parameterization 2: • Scaling model: spectrum shifts by scaling l

– allow amplitude a and scale l to vary

best fit: best fit: aa=0.93=0.93slice along a=1:slice along a=1:

//00== 1.021.02±±0.04 (0.04 (22=1)=1)

( )( ) ( ) ( )[ ]

0

0

sin

1

ss

EE

AAa

kgfa

C

=

=′

′′+′

=+

θθll

lll

ll l

• Scaling model: spectrum shifts by scaling l – allow amplitude a and scale l to vary

overtone 0.67 island: overtone 0.67 island: aa=0.69=0.69±±0.030.03

excluded by TTexcluded by TTand other priorsand other priors

other overtone islandsother overtone islands

also excludedalso excluded

• DASI EE 5-bin bandpowers (Leitch et al. 2004)– bin-bin covariance matrix plus approximate

window functions

a=0.5, 0.67 overtone islands:a=0.5, 0.67 overtone islands:

suppressed by DASIsuppressed by DASI

DASI phase lock:DASI phase lock:

//00== 0.94±0.060.94±0.06a=0.5 (low DASI)a=0.5 (low DASI)

CBI a=0.67 overtone island:CBI a=0.67 overtone island:

suppressed by DASI datasuppressed by DASI data

other overtone islandsother overtone islands

also excludedalso excluded

CBI+DASI phase lock:CBI+DASI phase lock:

//00== 1.00±0.031.00±0.03a=0.78a=0.78±0.15±0.15 (low DASI) (low DASI)

slice at: slice at: aa=1=1

== 2525°±°±3333°° rel. phase rel. phase

7.0- to 8.9- detection in amplitude of EE-mode polarizationand 3- rejection of “in phase” EE-TT spectra

a marginal result?I don’t think so!

apples & oranges: known uncertainties vs. blue-sky predictions of new technologies

Ey ~ Ea - Eb

Ex ~ Ea + Eb

Gx Gy (ExEy) ~ Gx Gy ( Ea2 - Eb

2 )

polarizers

Ga Ea2 Gb Eb

2

x

y

a b

EyEx

±

OMT

Correlation Polarimetry

Differencing Bolometers

Polarimetry Techniques

synchrotron 100 GHz

dust 100 GHz

WMAPBICEPQUIET1QUEST (QUaD)PlanckQUIET2

synchrotron 100 GHz

dust 100 GHz

Hivon