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Published August 20, 2009 | Published
Journal Article Open

Cosmological Parameters from the QUaD CMB Polarization Experiment


In this paper, we present a parameter estimation analysis of the polarization and temperature power spectra from the second and third season of observations with the QUaD experiment. QUaD has for the first time detected multiple acoustic peaks in the E-mode polarization spectrum with high significance. Although QUaD-only parameter constraints are not competitive with previous results for the standard six-parameter ΛCDM cosmology, they do allow meaningful polarization-only parameter analyses for the first time. In a standard six-parameter ΛCDM analysis, we find the QUaD TT power spectrum to be in good agreement with previous results. However, the QUaD polarization data show some tension with ΛCDM. The origin of this 1σ-2σ tension remains unclear, and may point to new physics, residual systematics, or simple random chance. We also combine QUaD with the five-year WMAP data set and the SDSS luminous red galaxies 4th data release power spectrum, and extend our analysis to constrain individual isocurvature mode fractions, constraining cold dark matter density, α_(cdmi) < 0.11 (95% confidence limit (CL)), neutrino density, α_(ndi) < 0.26 (95% CL), and neutrino velocity, α_(nvi) < 0.23 (95% CL), modes. Our analysis sets a benchmark for future polarization experiments.

Additional Information

© 2009. The American Astronomical Society. Received 2008 December 19; accepted 2009 May 11; published 2009 July 28. QUaD is funded by the National Science Foundation in the USA, through grants AST-0096778, ANT-0338138, ANT-0338335, and ANT-0338238, by the UK Science and Technology Facilities Council (STFC) and its predecessor the Particle Physics and Astronomy Research Council (PPARC), and by the Science Foundation Ireland. J.R.H. acknowledges the support of an NSF Graduate Research Fellowship, a Stanford Graduate Fellowship and a NASA Postdoctoral Fellowship. C.P. and J.E.C. acknowledge partial support from the Kavli Institute for Cosmological Physics through the grant NSF PHY-0114422. E.Y.W. acknowledges receipt of an NDSEG fellowship.Y.M. acknowledges support from a SUPAPrize studentship. P.G.C. acknowledges funding from the Fundação para a Ciência e a Tecnologia. M.Z. acknowledges support from a NASA Postdoctoral Fellowship. This work has made use of the resources provided by the Edinburgh Compute and Data Facility (ECDF) that is partially supported by the eDIKT initiative. We also thank Licia Verde and Joanna Dunkley for useful discussion.

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