Post on 12-Jan-2016
description
Update on QUaD
Sarah ChurchQUaD Collaboration
Funded: National Science Foundation Astronomy Program and Office of Polar Programs
Stanford University• Sarah Church (US PI)• Melanie Bowden (now industry)• James Hinderks (now Goddard) • Ben Rusholme (now IPAC)• Keith Thompson• Ed Wu
Cardiff University• Walter Gear (UK PI) • Peter Ade• Sujata Gupta• Simon Melhuish (now Manchester)• Lucio Piccirillo (now Manchester)• Nutan Rajguru (now industry)• Angiola Orlando (now Caltech)• Abigail Turner• Mike Zemcov (now Caltech)
Collège de France• Ken Ganga
U. of Chicago• Clem Pryke (Data Analysis Lead)• John Carlstrom• Tom Culverhouse• Robert Friedman• Erik Leitch (JPL)• Robert Schwarz (over winterer)
N.U.I Maynooth• Anthony Murphy• Gary Cahill• Creidhe O’Sullivan
U. of Edinburgh• Andy Taylor• Michael Brown (now Cambridge)• Patricia Castro (now Lisbon)• Yasin Memari
Caltech / JPL• Jamie Bock• John Kovac• Andrew Lange
The QUaD CassegrainTelescope
2.6m primary
Secondary supported with foam cone
Re-imaging lenses
“Deck” rotation axis
The QUaD Focal Plane
metal-mesh resonant grid filters define the band
JFETs at 4K
Focal plane at 250 mK
Load resistors
Corrugated feed
Bolometers
Vespel legs isolate the stages
440 mK plate
4K plate
QUaD Summary
Freq(GHz)
Beam(arcmin
)
No.feeds
FractionalBandwidt
h
NEQ per pair (K s1/2)
1005.1
(5.6)12 (9) 0.28 480
1503.7
(4.5)19
(17)0.27 440
Stokes Sampling
Azimuth scan
Rotation of the entire telescope
Difference 2 PSBs to get Q or U, depending on orientation
Rotate telescope and instrument about the optic axis (allowed rotation is +/-60 degrees) to change the orientation of instrumental polarization with respect to sky.
Scan in azimuth, reacquire source, rescan.
Very redundant observing strategy
Beams
No accessible planets Measured from several
sources HII regions (RCW38)
o Extended structure Quasar
o Dim and variable
5.1’ (100 GHz) 3.7’ (150 GHz) ~ 10% uncertainty
Polarization Calibration
Chopped thermal source with pol grid
Cross PolarCo Polar
Gain Calibration Relative Calibration
El nods: Frequent nods in elevation provides large correlated signal across all channels.
Cal source: Flip mirror inserts rotating polarized source into beam.
Row cals: Raster all pixels across RCW38.
Skydips, loadcurves Absolute Calibration
Temperature: Correlate full-season T-maps against BOOMERANG
Polarization: Use T calibration corrected by measured
Slightly processed data
Picture credit: Pryke
QUaD is a good polarimeterQUaD maps of Cen A
QUaD map of the Moon
Polarization levels in these maps are 1-2%
150 GHz temperature map
150 GHz temperature map
150 GHz Stokes U map
100 Degree Sidelobe ~ 1% of total power in
a narrow circular sidelobe at 100 deg. to the boresight
Source of contamination from the ground and the moon
Lead/Trail field differencing removes ground pickup
Data cuts remove moon contamination
Field differencing is used to mitigate ground pickup
Picture credit: PrykePicture credit: Pryke
150 GHz Field-differences Stokes U map
Smoothed maps show polarization
Picture credit: Wu
Smoothed maps show polarization
Picture credit: Wu
Data analysis methodPower Spectrum Determination
Monte-Carlo based analysis Noise only simulations, based on measured noise
correlation properties, used to correct noise bias in the power spectrum
Signal-only simulations, based on WMAP best fit parameters, are used to estimate the effects of sky cut and filtering
The scatter in the power spectrum from multiple simulations corrected as above gives the error bars on the band powers
Season 1 100GHz/150GHz Cross-correlationQUaD first year power spectra
One pipeline uses full spherical harmonic analysis using HEALPIX, other uses flat sky approx. and 2D FFTs
Season 1 100GHz/150GHz Cross-correlationQUaD first year power spectra
67 days mapping 60 square degrees of sky Only ~30% of final data set Submitted paper at arXiv:0705.2359 (Feb
10th ApJ) Bandpowers are publicly available
Observing Strategy Allows for Many Jack-knife Tests
Observing Strategy Allows for Many Jack-knife Tests
Power spectra are consistent with -CDM
QUaD cosmological parameter estimates Using the polarization data only
Using priors:0.0<h <1 <0.80.0<As<2.50<ns<2
Preview of next data release
Other science from 3rd season data
Measurements of galactic dust – spectral index and polarization
Map above shows 2 days of QUaD observations from season 3
Summary
QUaD first data published and power spectra are publicly available
Three observing seasons are complete Next data release probably ~ mid-late April Also work taking place on
High-ell T spectrum Polarized galactic emission Foreground limits