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CMB polarisation results from QUIET

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

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CMB polarisation results from QUIET

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  1. CMB polarisation results from QUIET Ingunn Kathrine Wehus 23rd Rencontres de Blois, 1/6 -11

  2. 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

  3. 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

  4. 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

  5. QUIET collaboration

  6. 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

  7. 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

  8. QUIET Patches

  9. Q-band observing hours

  10. 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

  11. Temperature maps – galactic centerQUIET vs WMAP

  12. CMB temperature observations

  13. QUIET vs WMAP – galactic center Stokes Q Stokes U

  14. QUIET vs WMAP – galactic plane Stokes Q Stokes U

  15. QUIET vs WMAP – CMB patch Stokes Q Stokes U

  16. Decomposition into E and B modes

  17. The EE power spectrum

  18. The BB power spectrum

  19. 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)

  20. 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

  21. W-band galactic center Stokes Q Stokes U

  22. 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

  23. Phase II power spectra forecasts Current Performance (noise, duty cycle, 1/f) Likely Improvements 0.018r0.005 10lensing35 Courtesy K. Smith

  24. 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

  25. First Q-band results: arXiv:1012.3191 • See http://quiet.uchicago.edu/ for more information QUIET

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