The detection of the imprint of filaments on cosmic microwave background lensing

TL;DR

This paper reports the first detection of cosmic microwave background lensing caused by filaments in the cosmic web, offering new insights into large-scale matter distribution and galaxy formation environments.

Contribution

It presents the first detection of filament-induced CMB lensing, a null test to confirm this detection, and a phenomenological model to interpret the signal and measure filament bias.

Findings

First detection of filament lensing in CMB data

Filament bias measured to be around 1.5

Null test confirms the detection's robustness

Abstract

Galaxy redshift surveys, such as 2dF, SDSS, 6df, GAMA and VIPERS, have shown that the spatial distribution of matter forms a rich web, known as the cosmic web. The majority of galaxy survey analyses measure the amplitude of galaxy clustering as a function of scale, ignoring information beyond a small number of summary statistics. Since the matter density field becomes highly non-Gaussian as structure evolves under gravity, we expect other statistical descriptions of the field to provide us with additional information. One way to study the non-Gaussianity is to study filaments, which evolve non-linearly from the initial density fluctuations produced in the primordial Universe. In our study, we report the first detection of CMB (Cosmic Microwave Background) lensing by filaments and we apply a null test to confirm our detection. Furthermore, we propose a phenomenological model to interpret the detected signal and we measure how filaments trace the matter distribution on large scales through filament bias, which we measure to be around 1.5. Our study provides a new scope to understand the environmental dependence of galaxy formation. In the future, the joint analysis of lensing and Sunyaev-Zel'dovich observations might reveal the properties of `missing baryons', the vast majority of the gas which resides in the intergalactic medium and has so far evaded most observations.