Istituto di Scienza e Tecnologie dell'Informazione     
Leach S. M., Cardoso J., Baccigalupi C., Barreiro R. B., Betoule M., Bobin J., Bonaldi A., De Zotti G., Delabrouille J., Dickinson C., Eriksen H. K., Gonzalez-Nuevo J., Hansen F. K., Herranz D., Le Jeune M., Lopez-Caniego M., Martinez-Gonzalez E., Massardi M., Melin J., Miville-Dechêne M., Patanchon G., Prunet S., Ricciardi S., Salerno E., Sanz J. L., Stark J., Stivoli F., Stolyarov V., Stompor R., Vielva P. Component separation methods for the Planck mission. Astronomy & Astrophysics. Preprint, 2008.
Context. The Planck satellite will map the full sky at nine frequencies from 30 to 857 GHz. The CMB intensity and polarization that are its prime targets are contaminated by foreground emission. Aims. The goal of this paper is to compare proposed methods for separating CMB from foregrounds based on their diff erent spectral and spatial characteristics, and to separate the foregrounds into 'components' of diff erent physical origin (Galactic synchrotron, freefree and dust emissions; extra-galactic and far-IR point sources; Sunyaev-Zeldovich e tc. etc). Methods. A component separation challenge has been organized, based on a set of realistically complex simulations of sky emission. Several methods including those based on internal template subtraction, maximum entropy method, parametric method, spatial and harmonic cross correlation methods, and independent component analysis have been tested. Results. Diff erent methods proved to be e ffective in cleaning the CMB maps from foreground contamination, in reconstructing maps of diff use Galactic emissions, and in detecting point sources and thermal Sunyaev-Zeldovich signals. The power spectrum of the residuals is, on the largest scales, four orders of magnitude lower than that of the input Galaxy power spectrum at the foreground minimum. The CMB power spectrum was accurately recovered up to the sixth acoustic peak. The point source detection limit reaches 100 mJy, and about 2300 clusters are detected via the thermal SZ e ect on two thirds of the sky. We have found that no single method performs best for all scientific objectives. Conclusions. We foresee that the final component separation pipeline for Planck will involve a combination of methods and iterations between processing steps targeted at di fferent objectives such as diff use component separation, spectral estimation and compact source extraction.
URL: http://arxiv.org/pdf/0805.0269v2
Subject Component Separation
Astrophysical Imaging
Cosmic Microwave Background
J.2 Physical sciences and engineering

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