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

  • Author(s): Ade, PAR
  • Aghanim, N
  • Ashdown, M
  • Aumont, J
  • Baccigalupi, C
  • Banday, AJ
  • Barreiro, RB
  • Bartolo, N
  • Basak, S
  • Battaner, E
  • Benabed, K
  • Benoit-Lévy, A
  • Bernard, JP
  • Bersanelli, M
  • Bielewicz, P
  • Bock, JJ
  • Bonaldi, A
  • Bonavera, L
  • Bond, JR
  • Borrill, J
  • Bouchet, FR
  • Boulanger, F
  • Burigana, C
  • Butler, RC
  • Calabrese, E
  • Cardoso, JF
  • Catalano, A
  • Chiang, HC
  • Christensen, PR
  • Clements, DL
  • Colombi, S
  • Colombo, LPL
  • Combet, C
  • Crill, BP
  • Curto, A
  • Cuttaia, F
  • Danese, L
  • Davis, RJ
  • De Bernardis, P
  • De Zotti, G
  • Delabrouille, J
  • Dickinson, C
  • Diego, JM
  • Doré, O
  • Ducout, A
  • Dupac, X
  • Elsner, F
  • Enßlin, TA
  • Eriksen, HK
  • Finelli, F
  • Forni, O
  • Frailis, M
  • Fraisse, AA
  • Franceschi, E
  • Galeotta, S
  • Galli, S
  • Ganga, K
  • Ghosh, T
  • Giard, M
  • Giraud-Héraud, Y
  • Gjerløw, E
  • González-Nuevo, J
  • Górski, KM
  • Gruppuso, A
  • et al.
Abstract

© ESO, 2016. The secondary cosmic microwave background (CMB) B-modes stem from the post-decoupling distortion of the polarization E-modes due to the gravitational lensing effect of large-scale structures. These lensing-induced B-modes constitute both a valuable probe of the dark matter distribution and an important contaminant for the extraction of the primary CMB B-modes from inflation. Planck provides accurate nearly all-sky measurements of both the polarization E-modes and the integrated mass distribution via the reconstruction of the CMB lensing potential. By combining these two data products, we have produced an all-sky template map of the lensing-induced 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 multipoles up to 2000. 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 measurement at a significance level of 12σ, which agrees with the theoretical expectation derived from the Planck best-fit Λ cold dark matter model. This unique nearly all-sky secondary B-mode template, which includes the lensing-induced information from intermediate to small (10 ≤ l ≤ 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 lensing-induced contribution to the measured total CMB B-modes.

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