BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization
Creators: name: Array, The Keck
name: Collaborations, BICEP2
name: :
name: Ade, P. A. R.
name: Ahmed, Z.
name: Aikin, R. W.
name: Alexander, K. D.
name: Barkats, D.
name: Benton, S. J.
name: Bischoff, C. A.
name: Bock, J. J.
name: Bowens-Rubin, R.
name: Brevik, J. A.
name: Buder, I.
name: Bullock, E.
name: Buza, V.
name: Connors, J.
name: Crill, B. P.
name: Duband, L.
name: Dvorkin, C.
name: Filippin, J. P.
name: Fliescher, S.
name: Grayson, J.
name: Halpern, M.
name: Harrison, S.
name: Hildebrandt, S. R.
name: Hilton, G. C.
name: Hui, H.
name: Irwin, K. D.
name: Kang, J.
name: Karkare, K. S.
name: Karpel, E.
name: Kaufman, J. P.
name: Keating, B. G.
name: Kefeli, S.
name: Kernasovskiy, S. A.
name: Kovac, J. M.
name: Kuo, C. L.
name: Leitch, E. M.
name: Lueker, M.
name: Megerian, K. G.
name: Namikawa, T.
name: Netterfield, C. B.
name: Nguyen, H. T.
name: O'Brient, R.
name: Ogburn, R. W.
name: Orlando, A.
name: Pryke, C.
name: Richter, S.
name: Schwarz, R.
name: Sheehy, C. D.
name: Staniszewski, Z. K.
name: Steinbach, B.
name: Sudiwala, R. V.
name: Teply, G. P.
name: Thompson, K. L.
name: Tolan, J. E.
name: Tucker, C.
name: Turner, A. D.
name: Vieregg, A. G.
name: Weber, A. C.
name: Wiebe, D. V.
name: Willmert, J.
name: Wong, C. L.
name: Wu, W. L. K.
name: Yoon, K. W.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present measurements of polarization lensing using the 150 GHz maps which include all data taken by the BICEP2 &amp; Keck Array CMB polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution ($\sim 0.5^\circ$), the excellent sensitivity ($\sim 3μ$K-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales ($\ell\leq 700$). From the auto-spectrum of the reconstructed potential we measure an amplitude of the spectrum to be $A^{ϕϕ}_{\rm L}=1.15\pm 0.36$ (Planck $Λ$CDM prediction corresponds to $A^{ϕϕ}_{\rm L}=1$), and reject the no-lensing hypothesis at 5.8$σ$, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields $A^{ϕϕ}_{\rm L}=1.13\pm 0.20$. These direct measurements of $A^{ϕϕ}_{\rm L}$ are consistent with the $Λ$CDM cosmology, and with that derived from the previously reported BK14 B-mode auto-spectrum ($A^{\rm BB}_{\rm L}=1.20\pm 0.17$). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B-modes previously reported by BICEP / Keck at intermediate angular scales ($150\lesssim\ell\lesssim 350$) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B-modes at these angular scales.
description: 12 pages, 8 figures