K. Ganga – CMB Science and Observations 1 Rencontres du Vietnam - 2006/08

The QuaDCMB Polarization

Experiment

K. GangaAPC

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The Collaboration● Stanford: M. Bowden, S.

Church, J. Hinderks, P. Marshall, B. Rusholme, K. Thompson, E. Wu

● Chicago: J. Carlstrom, T. Culverhouse, R. Friedmann, C. Pryke

● JPL/Caltech: J. Bock, J. Kovac, E. Leitch, A. Lange

● Pole: A. Day, R. Schwarz

● Cardiff: P. Ade, O. Mallie, S. Melhuish, A. Orlando, W. Gear, M. Zemcov

● ROE: P. Castro, M. Brown, A. Taylor

● UCL: N. Rajguru● Mancester: L. Piccirillo● Maynooth: G. Cahill, A.

Murphy, F. Noviello, C. O'Sullivan

● APC: K. Ganga

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The QUaD survey• The aim of QUaD:

– First high-resolution maps of E-type polarisation• l=75 – 2500

• Cosmological parameters (neutrinos, dark energy, inflation?)

– Limits on B-type polarisation from gravitational lensing– Say something about B-type polarisation from gravitational

waves• The QUaD environment:

– 2.6 m primary

– 62 PSBs at 250 mK

– Operates from South Pole on DASI mount

– Almost finished with second season.

– Hoping for one, and probably only one, more

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Optics

metal-meshfilters (Cardiff)

JFETs at 4K

Focal planeat 250 mK

Load resistors

Corrugated feed

Focal plane (Stanford)

• 31 Polarization Sensitive Bolometers• 12@100 GHz (~6.5')

• 19@150 GHz (~5')

Technologysimilar to

Planck

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Scanning Strategy

Between scans the focal plane can be

rotated on the sky by rotating the entire

telescope about the optic axis

We did 0 and 60 degrees for the first half of the season.

Now we're doing -30 and 30.

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1st season’s observationsEach hour of observations is split between a lead and trail field – separated by 0.5 hrs (7.5°) in RA – exact same scan pattern with respect to ground.

Two 8-hour CMB runs/day: 2nd run repeats same scan pattern as 1st with telescope rotated 60° about line of sight axis (deck angle rotation).

Relative calibration from source (RCW38) + “el-nods” (small el scan to inject atmospheric ramp).

99 days of CMB data taken in 1st season covering a 10°×6° patch of the B03 (low-foreground) deep field region.

Calibrate using BOOMERanG, which is in turn calibrated on WMAP.

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The South Pole

NSF NSFNSF

NSF

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The QUaD Telescope- QUaD is a classical Cassegrain design with 2.6m primary

- A foam cone supports the secondary mirror for clean polarization characteristics

- Outside work is kept to a minimum

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Atmospheric Noise

● The two detectors in a given assembly see essentially the same atmospheric signal: subtracting the two effectively eliminates the atmosphere, but retains the polarization signal– This cannot be used for total power measurements,

however

Filtered

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Moon

While this measurement is difficult to interpret quantitatively given the

obscuration of the primary mirror, it does give us an important

confirmation of the geometry of our focal plane and the detector orientations.

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QUaD Sky Coverage

100 sq deg

• Galactic dust map at 150 GHz

(Bowden, Taylor, et al 2003)

Obervable skyfrom South Pole.

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These show T, Q & U maps at 100 GHz for our full first season of data. A third order polynomial has been subtracted from each scan to remove low-f atmospheric noise, but that’s about all the filtering that has been applied.

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- These are the same maps, but at 150 GHz. Obviously, the sky is a bigger contaminant in T, but PSB differencing does a good job for the polarization fields.

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Field differencingDifference lead & trail fields to remove possible ground signal (sensitivity hit: S/N ↓ by √2).100 GHz T 150 GHz T

150 GHz Q 150 GHz U

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Redundant Processing

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- This set of images compares our very early maps to those of B2K and WMAP in the same region of sky.

- There is good concordance with previous measurements of this region of the sky.

- We will use the comparison with B2K to perform our final absolute calibration.

Comparison, Confirmation and Calibration

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Jacknives

Temperature map

Focal Plane AngleJackknife Map

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Foregrounds

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Predicted Spectra

l-space coverage of QUaD

Largest scales determined by sky coverage and scan strategy.

Smallest scales determined bybeam

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Jacknife power spectra – 150 GHz real /sims

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Power spectra from simulations

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Summary● First light in Feb. 2005● QUaD has observed for almost two seasons

– Should have one more● First season results should be out “soon”