CMB polarisation results from QUIET

Ingunn Kathrine Wehus 23rd Rencontres de Blois, 1/6 -11

CMB polarisation

• We can measure the polarisation of the CMB the same way as for light • The Stokes parameters quantify the polarization properties of a light ray – – – I = no filter at all Q = linear polarizer at 0 and 90 ° U = linear polarizer at -45 and 45 ° – V = circular polarizer • • • I is just the temperature Q and U combine to form E- and B-modes No known physical process can generate V-polarised CMB radiation

B-modes and inflation

• • • • • Stokes Q and U can be combined to E modes and B-modes Density fluctuations at last scattering produce E-modes Gravitational lensing turns E-modes into B modes at small scales Primordial gravitational waves produce B modes – Inflation predicts primordial gravitational waves B-modes never measured – The tensor-to-scalar ratio r parametrizes how much B-modes there are compared to E-modes – r gives the energy scale of inflation

QUIET (Q/U Imaging ExperimenT)

• • • • • QUIET is a groundbased experiment for measuring CMB polarisation – Constrains B-modes – Teaches us about inflation Only B-mode radiometer experiment – – – Different, and possibly better, systematics Unique radiometer on a chip technology Input to case studies for the next generation satellite Phase I (Pilot) – – 19 Q-band detectors (43 GHz) Aug 08 - May 09 91 W-band detectors (95 GHz) Jun 09 – Dec 10 Phase II (If funded) – ~500 detectors in 3 bands (32, 44 and 90 GHz) Measure the E- and B-mode spectra between

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– detection of lensing at more than 20σ – = 25 and 2500 constraining the tensor-to-scalar ratio r down to 0.01

QUIET collaboration

Chicago (KICP) Fermilab QUIET collaboration Manchester Oxford Oslo MPIfR-Bonn Stanford (KIPAC) Caltech JPL Columbia Princeton Miami KEK Observational Site Atacama, Chile 5 countries, 13 institutes, ~30 people

The site

• • • • • Located at 5080 m above sea level at the Chajnantor platau in the Atacama desert in Chile One of the driest places on earth..

– South pole has 40% lower PWV, but lower temperature results in comparable transmission – More of the sky is available than on south pole, and the same patch of sky can be observed from different angles. Good for systematics control – Accessible year round, day and night ..but still varying weather Control room Local inhabitants

QUIET Patches

Patch 2a Patch 4a Patch 6a Patch 7b All CMB Patch Gb Patch Gc Q-band observing hours Observing hours 905 703 837 223 2668 311 92 In total 3458 observation hours (77% cmb, 12% galaxy, 7% calib, 4% cut)

Two independent pipelines

• Pseudo-Cl (PCl) pipeline – Computationally less heavy; massive null-testing – Easy to simulate systematic errors • Maximum-likelihood (ML) pipeline – Produces optimally filtered map – Power spectrum calculated from exact likelihood – Needs the full covariance matrix from the previous step – Gives smaller and more accurate error bars

Temperature maps – galactic center QUIET vs WMAP

CMB temperature observations

QUIET vs WMAP – galactic center Stokes Q Stokes U

QUIET vs WMAP – galactic plane Stokes Q Stokes U

QUIET vs WMAP – CMB patch

Stokes Q Stokes U

Decomposition into E and B modes

The EE power spectrum

The BB power spectrum

Tensor-to-scalar ratio r

• • ML: r = 0.52+0.97−0.81.

PCL: r=0.35+1.06-0.87 (r < 2.2 at 95% confidence) (BICEP: r < 0.72 at 95% confidence)

Future prospects • • More Q-band papers to follow: – Foregrounds, point sources, instrumentation, data analysis W-band analysis now started – Optimized pipelines to handle more data – Null-testing ongoing

W-band galactic center

Stokes Q Stokes U

Future prospects • • • More Q-band papers to follow: – Foregrounds, point sources, instrumentation, data analysis W-band analysis now started – Optimized pipelines to handle more data – Null-testing ongoing Future phase II plans – Improved detectors under development at JPL

Phase II power spectra forecasts Current Performance (noise, duty cycle, 1/f) Likely Improvements 0.018

10   r lensing 0.005

35  Courtesy K. Smith

Summary

• CMB polarisation is a future main source of cosmological data – Detecting primordial gravitational waves will teach us about inflation • QUIET is among the most sensitive CMB B-mode experiments in the world: – Unique radiometer technology – Q-band receiver is world leading in published array sensitivity at 69 uK sqrt(s) – Excellent location • Q-band results show that everything is working – Power spectra consistent with LCDM – Current constraint on tensor-to-scalar ratio is r = 0.35 ± 1.0

• W-band results will be world leading when presented later this year • Phase II may possibly detect gravitational waves.

– Will constrain r below 0.01

• • First Q-band results: arXiv:1012.3191

See http://quiet.uchicago.edu/ for more information

QUIET