CMB lensing power spectrum estimation without instrument noise bias

Abstract

The power spectrum of cosmic microwave background (CMB) lensing will be measured to sub-percent precision with upcoming surveys, enabling tight constraints on the sum of neutrino masses and other cosmological parameters. Measuring the lensing power spectrum involves the estimation of the connected trispectrum of the four-point function of the CMB map, which requires the subtraction of a large Gaussian disconnected noise bias. This reconstruction noise bias receives contributions both from CMB and foreground fluctuations as well as instrument noise (both detector and atmospheric noise for ground-based surveys). The debiasing procedure therefore relies on the quality of simulations of the instrument noise which may be expensive or inaccurate. We propose a new estimator that makes use of at least four splits of the CMB maps with independent instrument noise. This estimator makes the CMB lensing power spectrum completely insensitive to any assumptions made in modeling or simulating the instrument noise. We show that this estimator, in many practical situations, leads to no substantial loss in signal-to-noise. We provide an efficient algorithm for its computation that scales with the number of splits $m$ as $\mathcal{O}(m^2)$ as opposed to a naive $\mathcal{O}(m^4)$ expectation.

18 pages, 4 figures, minor changes in v2 to match published version

References in corpus (8)

• Array Programming with NumPy
• Detection of Gravitational Lensing in the Cosmic Microwave Background
• Correlation of CMB with large-scale structure: II. Weak lensing
• Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements
• CMB temperature lensing power reconstruction
• Reconstructing Patchy Reionization from the Cosmic Microwave Background
• Full covariance of CMB and lensing reconstruction power spectra
• Fast Wiener filtering of CMB maps with Neural Networks

Cited by in corpus (4)

• Instrumental systematics biases in CMB lensing reconstruction: a simulation-based assessment
• Cosmological constraints using Minkowski functionals from the first year data of the Hyper Suprime-Cam
• Impact of Anisotropic Birefringence on Measuring Cosmic Microwave Background Lensing
• The Bias to Cosmic Microwave Background Lensing Reconstruction from the Kinematic Sunyaev-Zel'dovich Effect at Reionization