Bicep2/KECK ARRAY VIII: MEASUREMENT OF GRAVITATIONAL LENSING FROM LARGE-SCALE B-MODE POLARIZATION

Abstract

We present measurements of polarization lensing using the 150 GHz maps, which include all data taken by the BICEP2andKeck Array Cosmic Microwave Background polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution (~ 0 . 5), the excellent sensitivity (∼3μK-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales (  ℓ 700). From the auto-spectrum of the reconstructed potential, we measure an amplitude of the spectrum to be) and reject the no-lensing hypothesis at s 5.8 , which is the highest significance achieved to date using an EB lensing estimator. Taking ). 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 scales350) 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.

Maximum a posteriori CMB lensing reconstruction

“…6 The Planck number matches well the result of the B-mode delensing analysis performed by Ref. [31] on data.…”

“…Lensing estimators use these higher-order statistics to construct an integrated measure of the linear mass fluctuations in the Universe that cross-correlates to all traditional large-scale structure tracers. After the first direct detection of lensing in the CMB by the ACT team [2], the SPT [3], POLARBEAR [4], SPTpol [5], BICEP2-KECK [6] and Planck [7] collaborations have also reported the detection of the lensing signal and published band-powers. The most decisive detection yet was by the Planck satellite [8]: its full-sky coverage comes with a statistical power that simply cannot be matched at the present time.…”

Looking through the same lens: Shear calibration for LSST, Euclid, and WFIRST with stage 4 CMB lensing

“…It is a practical example of real synergy between overlapping surveys, where combining probes leads to improved systematics and not just a marginally higher signal-tonoise ratio. CMB lensing has been measured by the WMAP satellite [39,40], the Atacama Cosmology Telescope (ACT) [41][42][43][44], the South Pole Telescope (SPT) [45][46][47], POLARBEAR [48], the Planck satellite [49,50], and the BICEP 2/Keck Array [51]. In the future, Advanced ACT [52], SPT-3G [53], and a stage 4 ground-based CMB experiment (CMB S4) [54,55], as well as the Simons Observatory [56], will provide high fidelity maps of the CMB lensing convergence over a large fraction of the sky.…”

Status of Neutrino Properties and Future Prospects—Cosmological and Astrophysical Constraints

“…From the ground, the Atacama Cosmology Telescope (ACT) polarization-sensitive receiver and the South Pole Telescope (SPT) have been measuring with incredible accuracy CMB anisotropies at the smallest scales in temperature and polarization [16,17]. At degree and subdegree scales, the BICEP/Keck collaboration [18,19] and the POLARBEAR telescope [20] are looking at the faint CMB "B-mode" signal, containing information about both the early stages of the Universe (primordial B-modes) and the late time evolution (lensing B-modes). The Cosmology Large Angular Scale Surveyor (CLASS) [21] is working at mapping the CMB polarization field over 70% of the sky.…”