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

QUIET collaboration

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

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

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r 0.005 10 lensing 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