Detecting Electron Density Fluctuations from Cosmic Microwave Background Polarization using a Bispectrum Approach

TL;DR

This paper introduces a bispectrum-based method to extract electron density fluctuations from CMB polarization data, enabling detection of large scale structure effects with future experiments.

Contribution

It develops a novel bispectrum formalism using LSS tracers to isolate electron density fluctuations from dominant lensing signals in CMB polarization.

Findings

Bispectrum formalism effectively reconstructs EDFs and LSS cross correlations.

Next-generation experiments can detect EDF signatures with high significance.

Method reduces bias from lensing effects in EDF reconstruction.

Abstract

Recent progress in high sensitivity Cosmic Microwave Background (CMB) polarization experiments opens up a window on large scale structure (LSS), as CMB polarization fluctuations on small angular scales can arise from a combination of LSS and ionization fluctuations in the late universe. Gravitational lensing effects can be extracted from CMB datasets with quadratic estimators but reconstructions of electron density fluctuations (EDFs) with quadratic estimators are found to be significantly biased by the much larger lensing effects in the secondary CMB fluctuations. In this paper we establish a bispectrum formalism using tracers of LSS to extract the subdominant EDFs from CMB polarization data. We find that this bispectrum can effectively reconstruct angular band-powers of cross correlation between EDFs and LSS tracers. Next generation CMB polarization experiments in conjunction with galaxy surveys and cosmic infrared background experiments can detect signatures of EDFs with high significance.