Improving Small-Scale CMB Lensing Reconstruction

Abstract

Over the past decade, the gravitational lensing of the Cosmic Microwave Background (CMB) has become a powerful tool for probing the matter distribution in the Universe. The standard technique used to reconstruct the CMB lensing signal employs the quadratic estimator (QE) method, which has recently been shown to be suboptimal for lensing measurements on very small scales in temperature and polarization data. We implement a simple, more optimal method for the small-scale regime, which involves taking the direct inverse of the background gradient. We derive new techniques to make continuous maps of lensing using this "Gradient-Inversion" (GI) method and validate our method with simulated data, finding good agreement with predictions. For idealized simulations of lensing cross- and autospectra that neglect foregrounds, we demonstrate that our method performs significantly better than previous quadratic estimator methods in temperature; at $L=5000-9000$, it reduces errors on the lensing auto-power spectrum by a factor of $\sim 4$ for both idealized CMB-S4 and Simons Observatory-like experiments and by a factor of $\sim 2.6$ for cross-correlations of CMB-S4-like lensing reconstruction and the true lensing field. We caution that the level of the neglected small-scale foreground power, while low in polarization, is very high in temperature; though we briefly outline foreground mitigation methods, further work on this topic is required. Nevertheless, our results show the future potential for improved small-scale CMB lensing measurements, which could provide stronger constraints on cosmological parameters and astrophysics at high redshifts.

14 pages, 4 figures

References in corpus (2)

• Detection of Gravitational Lensing in the Cosmic Microwave Background
• Cosmological Information from Lensed CMB Power Spectra

Cited by in corpus (17)

• Quadratic estimators for CMB weak lensing
• Bayesian delensing delight: sampling-based inference of the primordial CMB and gravitational lensing
• The Benefits of CMB Delensing
• Baryonic feedback biases on fundamental physics from lensed CMB power spectra
• Probing galaxy bias and intergalactic gas pressure with KiDS Galaxies-tSZ-CMB lensing cross-correlations
• Baryonic effects on CMB lensing and neutrino mass constraints
• Mitigating Foreground Bias to the CMB Lensing Power Spectrum for a CMB-HD Survey
• Subtracting the kinetic Sunyaev-Zeldovich effect from the cosmic microwave background with surveys of large-scale structure
• Unveiling Neutrino Halos with CMB Lensing
• A new "temperature inversion" estimator to detect CMB patchy screening by large-scale structure
• Cluster profiles from beyond-the-QE CMB lensing mass maps
• CMB-HD: An Ultra-Deep, High-Resolution Millimeter-Wave Survey Over Half the Sky
• A halo model of extragalactic contamination to CMB lensing, delensing, and cross-correlations
• Prospects for studying the mass and gas in protoclusters with future CMB observations
• Maximum likelihood kinetic Sunyaev Zel'dovich velocity reconstruction
• Small Correlated Against Large Estimator (SCALE) for Cosmic Microwave Background Lensing
• Running the small-correlated-against-large estimator at scale: Applications of small-scale CMB lensing estimators on realistic simulations