Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-09-07
Astrophys.J.676:10-32,2008
Astronomy and Astrophysics
Astrophysics
23 pages, 16 figures; version accepted for publication in ApJ -- only minor changes, all clarifications. More information abou
Scientific paper
10.1086/525277
We describe and implement an exact, flexible, and computationally efficient algorithm for joint component separation and CMB power spectrum estimation, building on a Gibbs sampling framework. Two essential new features are 1) conditional sampling of foreground spectral parameters, and 2) joint sampling of all amplitude-type degrees of freedom (e.g., CMB, foreground pixel amplitudes, and global template amplitudes) given spectral parameters. Given a parametric model of the foreground signals, we estimate efficiently and accurately the exact joint foreground-CMB posterior distribution, and therefore all marginal distributions such as the CMB power spectrum or foreground spectral index posteriors. The main limitation of the current implementation is the requirement of identical beam responses at all frequencies, which restricts the analysis to the lowest resolution of a given experiment. We outline a future generalization to multi-resolution observations. To verify the method, we analyse simple models and compare the results to analytical predictions. We then analyze a realistic simulation with properties similar to the 3-yr WMAP data, downgraded to a common resolution of 3 degree FWHM. The results from the actual 3-yr WMAP temperature analysis are presented in a companion Letter.
Banday Anthony J.
Dickinson Cameron
Eriksen Hans Kristian
Górski Kris M.
Jewell Jeffrey B.
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