The Cosmic Background Imager – U. Sydney, 22 Oct 2004 2 CMB Polarization Results from the Cosmic...

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2The Cosmic Background Imager – U. Sydney, 22 Oct 2004

CMB Polarization Results from the

Cosmic Background ImagerSteven T. Myers

National Radio Astronomy Observatory

Socorro, NM

The Cosmic Background Imager

• A collaboration between– Caltech (A.C.S. Readhead PI, S. Padin PS.)– NRAO– CITA– Universidad de Chile– University of Chicago

• With participants also from– U.C. Berkeley, U. Alberta, ESO, IAP-Paris, NASA-MSFC,

Universidad de Concepción

• Funded by– National Science Foundation, the California Institute of

Technology, Maxine and Ronald Linde, Cecil and Sally Drinkward, Barbara and Stanley Rawn Jr., the Kavli Institute, and the Canadian Institute for Advanced Research

The CMB Landscape

The Cosmic Microwave Background

• Discovered 1965 (Penzias & Wilson)– 2.7 K blackbody– Isotropic– Relic of hot “big bang”– 3 mK dipole (Doppler)

• COBE 1992– Blackbody 2.725 K– Anisotropies ≤10-5

Thermal History of the Universe

Courtesy Wayne Hu – http://background.uchicago.edu

““First 3 minutes”:First 3 minutes”:very hot (10 million very hot (10 million °°K)K)like interior of Sunlike interior of Sunnucleosynthesis!nucleosynthesis!

After “recombination”:After “recombination”:cooler, transparent, cooler, transparent, neutral hydrogen gasneutral hydrogen gas

Before “recombination”:Before “recombination”:hot (3000hot (3000°°K)K)like surface of Sun like surface of Sun opaque, ionized plasmaopaque, ionized plasma

““Surface of last scattering” Surface of last scattering” TT≈≈30003000°°K zK z≈≈10001000THIS IS WHAT WE SEE AS THIS IS WHAT WE SEE AS THE CMB!THE CMB!

Angular Power Spectrum

• brightness fluctuations on surface of last scattering– due to the small (~0.1%) density variations– gravity causes flows (velocities)– radiation pressure resists compression bounces– acoustic waves!

• Fourier analysis– break angular ripple pattern into sine & cosine (FT)– look for power on particular angular frequencies– power spectrum = square of Fourier transform

• like a cosmic Spectrum Analyzer!

– acoustic waves + expansion fundamental + overtones• fundamental = scale of first compression since horizon crossing• scale set by sound crossing time at last scattering

CMB Acoustic Peaks

• Compression driven by gravity, resisted by radiation≈ “j ladder” series of harmonics + projection corrections

peaks: ~ peaks: ~ llss jjtroughs: ~ troughs: ~ llss ( (jj ±± ½½))

Fundamental: ~ Fundamental: ~ lls s

CMB Power Spectrum Features

• Power spectrum plots:

only transverse only transverse polarization can be polarization can be transmitted on scattering!transmitted on scattering!

CMB Polarization

• Due to quadrupolar intensity field at scattering

NOTE: polarization maximum NOTE: polarization maximum when velocity is maximum when velocity is maximum (out of phase with compression (out of phase with compression maxima)maxima)

CMB Polarization• E & B modes: even & odd parity modes on k-vector

– E (even parity, “gradient”) • from scalar density fluctuations predominant!

– B (odd parity, “curl”) • from gravity wave tensor modes, or secondaries

Polarization Power Spectrum

Hu & Dodelson ARAA 2002

Planck “error boxes”Planck “error boxes”

Note: polarization peaks Note: polarization peaks out of phase w.r.t. out of phase w.r.t. intensity peaksintensity peaks

B-modes from Inflation:B-modes from Inflation:Beyond Einstein missionBeyond Einstein missionkey mission goal.key mission goal.

The Cosmic Background Imager

The Instrument

• 13 90-cm Cassegrain antennas– 78 baselines

• 6-meter platform– baselines 1m – 5.51m

• 10 1 GHz channels 26-36 GHz– HEMT amplifiers (NRAO)

– cryogenic 6K, Tsys 20 K

• Single polarization (R or L)– polarizers from U. Chicago

• Analog correlators– 780 complex correlators

• Field-of-view 44 arcmin– image noise 4 mJy/bm 900s

• Resolution 4.5 – 10 arcmin– configuration dependent

CBI milestones• 1980’s

– 1984 OVRO 40m single-dish work (20 GHz maser Rx!)– 1987 genesis of idea for CMB interferometer

• 1990’s– 1992 OVRO systems converted to HEMTs– 1994 NSF proposal (funded 1995)– 1998 assembled and tested at Caltech– 1999 August shipped to Chile– 1999 November Chile first “light”

• 2000+– 2000 January routine observing begins– 2001 first paper; 2002 first year results; 2003 2yrs; 2004 pol– 2002 continued NSF funding to end of 2004– exploring funding prospects to operate until end of 2005

CBI Site – Northern Chilean Andes

• Elevation 16500 ft.!

CBI in Chile

The CBI Adventure…

• Steve Padin wearing the cannular oxygen system– because you never know when you

need to dig the truck out!

CBI 2000+2001, WMAP, ACBAR, BIMA

Readhead et al. ApJ, 609, 498 (2004)Readhead et al. ApJ, 609, 498 (2004)

astro-ph/0402359astro-ph/0402359

SZE SZE SecondarySecondaryCMB CMB

PrimaryPrimary

CBI PolarizationNew Results!

Brought to you by:A. Readhead, T. Pearson, C. Dickinson (Caltech)

S. Myers, B. Mason (NRAO),J. Sievers, C. Contaldi, J.R. Bond (CITA)

P. Altamirano, R. Bustos, C. Achermann (Chile)& the CBI team!

plus guest appearance by DASI !

dmdlvmuljemlIvuV ..2.),(),(

Interferometers

• Spatial coherence of radiation pattern contains information about source structure– Correlations along wavefronts

• Equivalent to masking parts of a telescope aperture– Sparse arrays = unfilled aperture– Resolution at cost of surface brightness sensitivity

• Correlate pairs of antennas– “visibility” = correlated fraction of total signal

• Fourier transform relationship with sky brightness– Van Cittert – Zernicke theorem

Polarization Interferometry

• CBI receivers can observe either RCP or LCP– correlation products RR, RL, LR, or LL from antenna pair

• Correlations to Stokes parameters (I,Q,U,V) :

• co-polar: RR = I + V LL = I – V – CMB not circularly polarized, ignore V (RR = LL = I)– co-polar correlations measure intensity (CMB temperature)

• cross-polar: RL = [Q + i U] e-i2 LR = [Q – i U] ei2 – cross-polar visibilities measure linear polarization– electric vector position angle EVPA = ½ tan-1(U/Q)– rotates with parallactic angle of detector on sky

Polarization Interferometry

• Stokes I,Q,U to E and B:

• Q + i U = [E + i B] ei2 RL = [E + i B] ei2( – counter-rotates with wave vector angle = ½ tan-1 (v/u)

• visibility covariances:– <RR RR*> = TT <RR RL*> = TE <RL RL*> = EE + BB

• interferometry works in Fourier domain– multipole l = 2 B / for baseline B– power spectrum from amplitude of visibility covariances– circularly polarized interferometer “directly” measures E and B!

2002 DASI & 2003 WMAP Polarization

Carlstrom et al. 2003 astro-ph/0308478

DASI 3-year polarization results

• Leitch et al. 2004 (astro-ph/0409357) 16Sep04! 16Sep04! – EE 6.3 σ – TE 2.9 σ – consistent w/ WMAP+ext model– BB consistent with zero– no foregrounds yet!

CBI & DASI Fields

galactic projection – image WMAP “synchrotron” (Bennett et al. 2003)

CBI Current Polarization Data

• Observing since Sep 2002 (processed to May 2004)– compact configuration, maximum sensitivity

CBI Current Polarization Data

• Four mosaics = 02h, 08h, 14h, 20h at = 0° – 02h, 08h, 14h 6 x 6 fields, 20h deep strip 6 fields , 45’ centers

• Scan subtraction/projection– observe scan of 6 fields, 3m apart = 45’, remove mean

• lose only 1/6 data to differencing (cf. ½ previously)

• Point source projection (important for TT)– list of NVSS sources (extrapolation to 30 GHz unknown)– need 30 GHz GBT measurements to know brightest

• Massive computations parallel codes– grid visibilities and max. likelihood (Myers et al. 2003)– using 256 node/ 512 proc McKenzie cluster at CITACITA

New: CBI Polarization Power Spectra

• 7-band fits (l = 150)• 10-band fits (l = 100)

New: Data Tests

• Test robustness to systematic effects, such as:– instrumental effects (amplitude, polarization)– foregrounds (synchrotron, free-free, dust)

• Numerous 2 and noise tests– few discrepant days found no difference to results

• Conduct series of splits and “jack-knife” tests, e.g.:– primary vs. secondary calibrators (calibration consistency)– first half vs. second half of data (time-variable instrument)– “jack-knife” on antennas (bad single antenna)– “jack-knife” on fields (bad single field)– high vs. low frequency channels (e.g. foregrounds)

NO SIGNIFICANT DEVIATIONS FOUND!

New: Shaped Cl fits

• Use WMAP’03 best-fit Cl in signal covariance matrix– bandpower is then relative to fiducial power spectrum– compute for single band encompassing all ls

• Results for CBI data (sources projected from TT only)– qB = 1.22 ± 0.21 (68%)

– EE likelihood vs. zero : equivalent significance 8.9 σ

• Conservative - project subset out in polarization also– qB = 1.18 ± 0.24 (68%)

– significance 7.0 σ

k b cdm ns m h

CBI Mosaic Observation

THE PILLARS OF INFLATION

1) super-horizon (>2°) anisotropies2) acoustic peaks and harmonic pattern (~1°)3) damping tail (<10')4) Gaussianity5) secondary anisotropies6) polarization7) gravity waves

But … to do this we need to measure a signal which is 3x107 timesweaker than the typical noise!

geometry baryonic fraction cold dark matter primordial dark energy matter fraction Hubble Constant optical depthof the protons, neutrons not protons and fluctuation negative press- size & age of the to last scatt-universe neutrons spectrum ure of space universe ering of cmb

The CBI measures these fundamental constants of cosmology:

New: CBI Polarization Parameters

• use fine bins (l = 75) + window functions (l = 25) • cosmological models vs. data using MCMC

– modified COSMOMC (Lewis & Bridle 2002)

• Include:– WMAP TT & TE– WMAP + CBI’04 TT & EE (Readhead et al. 2004b = new!)– WMAP + CBI’04 TT & EE l <1000

+ CBI’02 TT l >1000 (Readhead et al. 2004a) [overlaps ‘04]

New: CBI Polarization Parameters

• use fine bins (l = 75) + window functions (l = 25) • Include:

– WMAP TT & TE– CBI 2004 Pol TT, EE (Readhead et al. 2004b = new)– CBI 2001-2002 TT (Readhead et al. 2004a)

• NOTE: parameter constraints dominated by higher precision TT from CBI 2001-2002 data!

• NOTE: parameter constraints dominated by higher precision TT data! To discern what polarization data is adding, will need to be more subtle…

Cosmology from EE Polarization

• The New Standard Cosmological Model ™– EE “predictable” from TT– constraints dominated by more precise TT measurements

• Beyond the Standard Model– derive key parameters from EE alone – check consistency– add new ingredients (e.g. isocurvature) later…

Example: Acoustic Overtone Pattern

• Sound crossing angular size at photon decoupling– fiducial model WMAP+ext : θ0 = 1.046

WMAPWMAP

WMAP+CBI’04WMAP+CBI’04

WMAP+CBI’04+CBI’02WMAP+CBI’04+CBI’02

grand unified:grand unified:

θθ == 1.0441.044±0.005±0.005

θθ//θθ00 = = 0.998±0.0050.998±0.005(WMAP+CBI’04+CBI’02)(WMAP+CBI’04+CBI’02)

New: CBI EE Polarization Phase

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

= 0= 0°° : EE prediction: EE prediction = 180= 180°°: aligned with TT: aligned with TT

• Peaks in EE should be offset one-half cycle vs. TT – fix amplitude a=1 and allow phase to vary

slice at: slice at: aa=1=1

== 2525°±°±3333°° rel. phase ( rel. phase (22=1)=1)

22(1, 0(1, 0°°)=0.56)=0.56

• Peaks in EE should be offset one-half cycle vs. TT– allow amplitude a and phase to vary

best fit: best fit: aa=0.94=0.94

== 2424°±°±3333°° ( (22=1)=1)

22(1, 0(1, 0°°)=0.56)=0.56

• Scaling model: spectrum shifts by scaling l – same envelope f,g as before

fiducial model:fiducial model:

θθ00== 1.0461.046(“WMAP+ext”)(“WMAP+ext”)

θθ sound crossingsound crossingangular scaleangular scale

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

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

best fit: best fit: aa=0.93=0.93

slice along a=1:slice along a=1:

θθ//θθ00== 1.021.02±±0.04 (0.04 (22=1)=1)

zoom in: zoom in:

± one-half cycle± one-half cycle

New: CBI, DASI, Capmap

New: DASI EE Polarization Phase

• Use 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:

θθ//θθ00== 0.94±0.060.94±0.06a=0.5 (low DASI)a=0.5 (low DASI)

New: CBI + DASI EE Phase

• Combined constraints on θ model:– DASI (Leitch et al. 2004) & CBI (Readhead et al. 2004)

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:

θθ//θθ00== 1.00±0.031.00±0.03a=0.78a=0.78±0.15±0.15 (low DASI) (low DASI)

Conclusions

• CMB polarization interferometry (CBI,DASI)– straightforward analysis {RR,RL} → {TT,EE,BB,TE}– polarization systematics minimized

• CMB polarization results– EE power spectrum measured

• consistent with Standard Cosmological Model™

– EE acoustic spectrum• peaks phase one-half cycle offset from TT

• sound crossing angular scale independently consistent (3%)

– BB null, no polarized foregrounds detected– TE difficult to extract in wide bins

• more data, narrower bins

CBI Polarization Projections

Future

• CBI– 6 months more data in hand finer l bins– more detailed papers: data tests, analysis, parameters– run to end of 2005 (pending funding)– also: SZE clusters (e.g. Udomprasert et al. 2004)

• Beyond CBI QUIET– detectors are near quantum & bandwidth limit – need more!– but: need clean polarization (low stable instrumental effects)– large format (1000 els.) coherent (MMIC) detector array– polarization B-modes! (at least the lensing signal)

• Further Beyond– Beyond Einstein (save the Bpol mission!)

SZE with CBI: z < 0.1 clusters

P. Udomprasert thesis (Caltech)

The CBI Collaboration

Caltech Team: Tony Readhead (Principal Investigator), John Cartwright, Clive Dickinson, Alison Farmer, Russ Keeney, Brian Mason, Steve Miller, Steve Padin (Project Scientist), Tim Pearson, Walter Schaal, Martin Shepherd, Jonathan Sievers, Pat Udomprasert, John Yamasaki.Operations in Chile: Pablo Altamirano, Ricardo Bustos, Cristobal Achermann, Tomislav Vucina, Juan Pablo Jacob, José Cortes, Wilson Araya.Collaborators: Dick Bond (CITA), Leonardo Bronfman (University of Chile), John Carlstrom (University of Chicago), Simon Casassus (University of Chile), Carlo Contaldi (CITA), Nils Halverson (University of California, Berkeley), Bill Holzapfel (University of California, Berkeley), Marshall Joy (NASA's Marshall Space Flight Center), John Kovac (University of Chicago), Erik Leitch (University of Chicago), Jorge May (University of Chile), Steven Myers (National Radio Astronomy Observatory), Angel Otarola (European Southern Observatory), Ue-Li Pen (CITA), Dmitry Pogosyan (University of Alberta), Simon Prunet (Institut d'Astrophysique de Paris), Clem Pryke (University of Chicago).

The CBI Project is a collaboration between the California Institute of Technology, the Canadian Institute for Theoretical Astrophysics, the National Radio Astronomy Observatory, the University of Chicago, and the Universidad de Chile. The project has been supported by funds from the National Science Foundation, the California Institute of Technology, Maxine and Ronald Linde, Cecil and Sally Drinkward, Barbara and Stanley Rawn Jr., the Kavli Institute,and the Canadian Institute for Advanced Research.

The Cosmic Background Imager – U. Sydney, 22 Oct 2004 2 CMB Polarization Results from the Cosmic...

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