CMB polarisation results from QUIET

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CMB polarisation results from QUIET

• Ingunn Kathrine Wehus
• 23rd 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 20s
• constraining the tensor-to-scalar ratio r down to
  0.01

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QUIET collaboration
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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
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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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Q-band observing hours
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 In total 3458 observation hours (77 cmb, 12 galaxy, 7 calib, 4 cut)
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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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Tensor-to-scalar ratio r

• ML r 0.520.97-0.81.
• PCL r0.351.06-0.87 (r lt 2.2 at 95
  confidence)
• (BICEP r lt 0.72
  at 95 confidence)

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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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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
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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.

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• First Q-band results arXiv1012.3191
• See http//quiet.uchicago.edu/ for more
  information

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