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Published byLinette Armstrong Modified over 9 years ago
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Update on QUaD Sarah Church QUaD Collaboration Funded: National Science Foundation Astronomy Program and Office of Polar Programs
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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
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The QUaD CassegrainTelescope 2.6m primary Secondary supported with foam cone Re-imaging lenses “Deck” rotation axis
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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
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QUaD Summary Freq (GHz) Beam (arcmin) No. feeds Fractional Bandwidth NEQ per pair ( K s 1/2 ) 1005.1 (5.6)12 (9)0.28480 1503.7 (4.5)19 (17)0.27440
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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
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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
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Polarization Calibration Chopped thermal source with pol grid Cross PolarCo Polar
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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
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Slightly processed data Picture credit: Pryke
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QUaD is a good polarimeter QUaD maps of Cen A QUaD map of the Moon Polarization levels in these maps are 1-2%
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150 GHz temperature map
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150 GHz Stokes U map
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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
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Field differencing is used to mitigate ground pickup Picture credit: Pryke
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150 GHz Field-differences Stokes U map
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Smoothed maps show polarization Picture credit: Wu
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Smoothed maps show polarization Picture credit: Wu
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Data analysis method Power 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
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Season 1 100GHz/150GHz Cross-correlation QUaD first year power spectra One pipeline uses full spherical harmonic analysis using HEALPIX, other uses flat sky approx. and 2D FFTs
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Season 1 100GHz/150GHz Cross-correlation QUaD 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 10 th ApJ) Bandpowers are publicly available
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Observing Strategy Allows for Many Jack-knife Tests
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Power spectra are consistent with -CDM
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QUaD cosmological parameter estimates Using the polarization data only Using priors: 0.0<h <1 <0.8 0.0<A s <2.5 0<n s <2
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Preview of next data release
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Other science from 3 rd season data Measurements of galactic dust – spectral index and polarization Map above shows 2 days of QUaD observations from season 3
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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
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