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Bayesian Analysis of the Low-Resolution Polarized 3 Year WMAP Sky Maps

Eriksen, H. K. and Huey, Greg and Banday, A. J. and Górski, K. M. and Jewell, J. B. and O'Dwyer, I. J. and Wandelt, B. D. (2007) Bayesian Analysis of the Low-Resolution Polarized 3 Year WMAP Sky Maps. Astrophysical Journal Letters, 665 (1). L1-L4. ISSN 2041-8205. doi:10.1086/521191.

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We apply a previously developed Gibbs sampling framework to the foreground-corrected 3 yr WMAP polarization data and compute the power spectrum and residual foreground template amplitude posterior distributions. We first analyze the co-added Q- and V-band data, and compare our results to the likelihood code published by the WMAP team. We find good agreement, and thus verify the numerics and data-processing steps of both approaches. However, we also analyze the Q- and V-band data separately, allowing for nonzero EB cross-correlations and including two individual foreground template amplitudes tracing synchrotron and dust emission. In these analyses, we find tentative evidence of systematics: The foreground tracers correlate with each of the Q- and V-band sky maps individually, although not with the co-added QV map; there is a noticeable negative EB cross-correlation at l ≾ 16 in the V-band map; and finally, when relaxing the constraints on EB and BB, noticeable differences are observed between the marginalized band powers in the Q and V bands. Further studies of these features are imperative, given the importance of the low-l EE spectrum on the optical depth of reionization τ and the spectral index of scalar perturbations ns.

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Additional Information:© 2007. The American Astronomical Society. Received 2007 May 24; accepted 2007 June 27; published 2007 July 31. Print publication: Issue 1 (2007 August 10). We wish to thank David Larson for his contributions during the early phases of this project. We acknowledge use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA). We acknowledge use of the HEALPix software (Górski et al. 2005) and analysis package for deriving the results in this paper. This work was partially performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. H.K.E. acknowledges financial support from the Research Council of Norway. B.D.W. acknowledges support by NSF grant 0507676, the Friedrich Wilhelm Bessel Research Prize by the Alexander v. Humboldt foundation, and NASA subcontract 1236748.
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Research Council of NorwayUNSPECIFIED
National Science FoundationAST 0507676
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:cosmic microwave background; cosmology: observations; methods: numerical
Issue or Number:1
Record Number:CaltechAUTHORS:ERIapjl07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13004
Deposited By: Archive Administrator
Deposited On:15 Jan 2009 04:36
Last Modified:08 Nov 2021 22:34

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