Planck intermediate results. XLI. A map of lensing-induced B-modes

Abstract : The lensing-induced $B$-mode signal is a valuable probe of the dark matter distribution integrated back to the last-scattering surface, with a broad kernel that peaks at $z\simeq2$. It also constitutes an important contaminant for the extraction of the primary CMB $B$-modes from inflation. Combining all-sky coverage and high resolution and sensitivity, Planck provides accurate nearly all-sky measurements of both the polarization $E$-mode signal and the integrated mass distribution via the reconstruction of the CMB gravitational lensing. By combining these two data products, we have produced an all-sky template map of the secondary CMB $B$-modes using a real-space algorithm that minimizes the impact of sky masks. The cross-correlation of this template with an observed (primordial and secondary) $B$-mode map can be used to measure the lensing $B$-mode power spectrum at all angular scales. In particular when cross-correlating with the $B$-mode contribution directly derived from the Planck polarization maps, we obtain lensing-induced $B$-mode power spectrum measurements at a significance of $12\,\sigma$, which are in agreement with the theoretical expectation derived from the \Planck\ best-fit $\Lambda$CDM model. This unique nearly all-sky secondary $B$-mode template, which includes the lensing-induced information from intermediate to small ($10\lesssim \ell\lesssim 1000$) angular scales, is delivered as part of the Planck 2015 public data release. It will be particularly useful for experiments searching for primordial $B$-modes, such as BICEP2/Keck Array or LiteBIRD, since it will enable an estimate to be made of the secondary (i.e., lensing) contribution to the measured total CMB $B$-modes.
Document type :
Journal articles

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Submitted on : Thursday, December 10, 2015 - 10:53:39 AM
Last modification on : Monday, December 21, 2020 - 4:04:12 PM

Citation

P. A. R. Ade, O. Perdereau, M. Tristram, A. Catalano, C. Combet, et al.. Planck intermediate results. XLI. A map of lensing-induced B-modes. Astronomy and Astrophysics - A&A, EDP Sciences, 2016, 596, pp.A102. ⟨10.1051/0004-6361/201527932⟩. ⟨in2p3-01241228⟩

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