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Physical Review D 85 (2012) 083006
Astrophysical foregrounds and primordial tensor-to-scalar ratio constraints from cosmic microwave background B-mode polarization observations
J. Errard1, R. Stompor1

We study the effects of astrophysical foregrounds on the ability of Cosmic Microwave Background B-mode polarization experiments to constrain the primordial tensor-to-scalar ratio, r. To clean the foreground contributions we use parametric, maximum likelihood component separation technique, and consider experimental setups optimized to render a minimal level of the foreground residuals in the recovered CMB map. We consider nearly full-sky observations, include two diffuse foreground components, dust and synchrotron, and study cases with and without calibration errors, spatial variability of the foreground properties, and partial or complete B-mode lensing signal removal. In all these cases we find that in the limit of an arbitrarily low noise level and in the absence of the systematic effects, due to the instrument or modeling, the foreground residuals do not lead to a limit on the lowest detectable value of r. Nevertheless, the need to control the foreground residuals will play a major role in determining the minimal noise levels necessary to permit a robust detection of r(≲0.1) and therefore in optimizing and forecasting the performance of the future missions. For noise levels corresponding to current and proposed experiments, the foreground residuals are found non-negligible and potentially can significantly affect our ability to set constraints on r. We furthermore show how in some of these cases the constraints can be significantly improved on by restricting the post-component separation processing to a smaller sky area. This procedure applied to a case of a COrE-like satellite mission is shown to result potentially in more than an order of magnitude improvement in the detectable value of r. Our conclusions are found to be independent on the assumed overall normalization of the foregrounds and only quantitatively depend on specific parametrizations assumed for the foreground components. They however assume sufficient knowledge of the experimental bandpasses as well as foreground component scaling laws.
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique
Background radiations – Observational cosmology
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