Detectability of the cross-correlation between CMB lensing and stochastic GW background from compact object mergers

TL;DR

This paper explores the potential of cross-correlating CMB lensing with the stochastic gravitational-wave background to reduce noise and improve detection prospects of anisotropies caused by large-scale structure, though detection remains challenging.

Contribution

It introduces a novel framework for modeling GW source distribution and assesses the cross-correlation with CMB lensing to mitigate shot noise effects.

Findings

Significant correlation between SGWB energy density and CMB lensing convergence.

Cross-correlation reduces instrumental and shot noise impact.

Detection of intrinsic SGWB anisotropies remains unlikely with current S/N levels.

Abstract

The anisotropies of the Stochastic Gravitational-Wave Background (SGWB) produced by merging compact binaries constitute a possible new probe of the Large-Scale Structure (LSS). However, the significant shot noise contribution caused by the discreteness of the GW sources and the poor angular resolution of the instruments hamper the detection of the intrinsic anisotropies induced by the LSS. In this work, we investigate the potential of cross-correlating forthcoming high precision measurements of the SGWB energy density and the Cosmic Microwave Background (CMB) lensing convergence to mitigate the effect of shot noise. Combining a detailed model of stellar and galactic astrophysics with a novel framework to distribute the GW emitters in the sky, we compute the auto- and cross-correlation power spectra for the two cosmic fields, evaluate the shot noise contribution and predict the signal-to-noise ratio. The results of our analysis show that the SGWB energy density correlates significantly with the CMB lensing convergence and that the cross-correlation between these two cosmic fields reduces the impact of instrumental and shot noise. Unfortunately, the S/N is not high enough to detect the intrinsic SGWB anisotropies. Nevertheless, a network composed of both present and future generation GW interferometers, operating for at least 10 yrs, should be able to measure the shot noise contribution.