Journal Article

Large-scale polarized foreground component separation for <i>Planck</i>

Charmaine Armitage-Caplan, Joanna Dunkley, Hans Kristian Eriksen and Clive Dickinson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 418, issue 3, pages 1498-1510
Published in print December 2011 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI:
Large-scale polarized foreground component separation for Planck

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We use Bayesian component estimation methods to examine the prospects of large-scale polarized map and cosmological parameter estimation with simulated Planck data assuming simplified white noise properties. The sky signal is parametrized as the sum of the cosmic microwave background (CMB), synchrotron emission, and thermal dust emission. The synchrotron and dust emission components are modelled as power laws in frequency, with a spatially varying spectral index for synchrotron and a uniform index for dust. Using the Gibbs sampling technique, we estimate the linear polarization Q and U posterior amplitudes of the CMB, synchrotron and dust maps as well as the two spectral indices in ∼4° pixels. We use the recovered CMB map and its covariance in an exact pixel likelihood algorithm to estimate the optical depth to reionization τ, the tensor-to-scalar ratio r, and to construct conditional likelihood slices for CEE and CBB. Given our foreground model, we find σ(τ) ≈ 0.004 for τ= 0.1, σ(r) ≈ 0.03 for a model with r= 0.1, and a 95 per cent upper limit of r < 0.02 for r= 0.0.

Keywords: cosmic background radiation; cosmological parameters; cosmology: observations

Journal Article.  6802 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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