A Demonstration of Improved Constraints on Primordial Gravitational Waves with Delensing

Abstract

We present a constraint on the tensor-to-scalar ratio, $r$, derived from measurements of cosmic microwave background (CMB) polarization $B$-modes with "delensing," whereby the uncertainty on $r$ contributed by the sample variance of the gravitational lensing $B$-modes is reduced by cross-correlating against a lensing $B$-mode template. This template is constructed by combining an estimate of the polarized CMB with a tracer of the projected large-scale structure. The large-scale-structure tracer used is a map of the cosmic infrared background derived from Planck satellite data, while the polarized CMB map comes from a combination of South Pole Telescope, BICEP/Keck, and Planck data. We expand the BICEP/Keck likelihood analysis framework to accept a lensing template and apply it to the BICEP/Keck data set collected through 2014 using the same parametric foreground modelling as in the previous analysis. From simulations, we find that the uncertainty on $r$ is reduced by $\sim 10\%$, from $\sigma (r)$= 0.024 to 0.022, which can be compared with a $\sim 26\%$ reduction obtained when using a perfect lensing template. Applying the technique to the real data, the constraint on $r$ is improved from $r_{0.05}<0.090$ to $r_{0.05}<0.082$ (95\% C.L.). This is the first demonstration of improvement in an $r$ constraint through delensing.

23 pages, 11 figures; match published version

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Cited by in corpus (22)

• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• The Benefits of CMB Delensing
• The Simons Observatory: Constraining inflationary gravitational waves with multi-tracer B-mode delensing
• CMB-S4: Iterative Internal Delensing and $r$ Constraints
• The Simons Observatory: Galactic Science Goals and Forecasts
• Foreground Separation and Constraints on Primordial Gravitational Waves with the PICO Space Mission
• First Constraints on the Epoch of Reionization Using the non-Gaussianity of the Kinematic Sunyaev-Zel{'}dovich Effect from the South Pole Telescope and {\it Herschel}-SPIRE Observations
• LiteBIRD Science Goals and Forecasts: Improving Sensitivity to Inflationary Gravitational Waves with Multitracer Delensing
• QUIJOTE scientific results -- VIII. Diffuse polarized foregrounds from component separation with QUIJOTE-MFI
• The impact of extragalactic foregrounds on internal delensing of CMB B-mode polarization
• Delensing of Cosmic Microwave Background Polarization with machine learning
• Subtracting the kinetic Sunyaev-Zeldovich effect from the cosmic microwave background with surveys of large-scale structure
• QUIJOTE scientific results -- V. The microwave intensity and polarisation spectra of the Galactic regions W49, W51 and IC443
• Simulating Calibration and Beam Systematics for a Future CMB Space Mission with the TOAST Package
• A halo model of extragalactic contamination to CMB lensing, delensing, and cross-correlations
• Detecting deviations from Gaussianity in high-redshift CMB lensing maps
• Improving Cosmic Birefringence Constraints via Delensing
• Delensing for Precision Cosmology: Optimizing Future CMB B-mode Surveys to Constrain r
• Enhancing Primordial B-mode Detection: Comprehensive Delensing Pipelines for Improved Sensitivity to $r$
• LiteBIRD science goals and forecasts: improved full-sky reconstruction of the gravitational lensing potential through the combination of Planck and LiteBIRD data
• Delensing CMB B-modes using galaxy surveys: the effect of galaxy bias and matter clustering non-linearities
• Receiver development for BICEP Array, a next-generation CMB polarimeter at the South Pole