cmb polarisation results from quiet
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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CMB polarisation results from QUIET
Ingunn Kathrine Wehus23rd Rencontres de Blois, 1/6 -11
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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
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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
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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
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QUIET collaboration
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Miami
Chicago (KICP)Fermilab
ColumbiaPrinceton
ManchesterOxford Oslo MPIfR-Bonn
KEK
Observational Site Atacama, Chile
5 countries, 13 institutes, ~30 people5 countries, 13 institutes, ~30 people
CaltechJPL
Stanford(KIPAC)
QUIET collaboration
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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
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QUIET Patches
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Observing hours
Patch 2a 905
Patch 4a 703
Patch 6a 837
Patch 7b 223
All CMB 2668
Patch Gb 311In total 3458 observation hours
(77% cmb, 12% galaxy, 7% calib, 4% cut)Patch Gc 92
Q-band observing hours
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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
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Temperature maps – galactic centerQUIET vs WMAP
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CMB temperature observations
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QUIET vs WMAP – galactic center
Stokes Q Stokes U
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QUIET vs WMAP – galactic plane
Stokes Q Stokes U
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QUIET vs WMAP – CMB patch
Stokes Q Stokes U
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Decomposition into E and B modes
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The EE power spectrum
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The BB power spectrum
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• 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)
Tensor-to-scalar ratio r
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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
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W-band galactic center
Stokes Q Stokes U
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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
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Current Performance(noise, duty cycle, 1/f) Likely Improvements
0.018r 0.00510 lensing 35
Phase II power spectra forecasts
Courtesy K. Smith
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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
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QUIET
• First Q-band results: arXiv:1012.3191• See http://quiet.uchicago.edu/ for more information
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