Detectability of the Cross-Correlation between CMB Lensing and Stochastic GW Background from Compact Object Mergers

Giulia Capurri,Carlo Baccigalupi,Andrea Lapi

doi:10.3390/universe8030160

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 hampers 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.

Highlights

The direct detection of gravitational waves (GW) [1] achieved by the network of ground-based interferometers constituted by the Advanced Laser Interferometer Gravitatio nal-Wave Observatory (LIGO) [2], Advanced Virgo [3] and the Kamioka Gravitational Wave Detector (KAGRA) [4] has opened a new observational window on the Universe
We investigate the potential of cross-correlating forthcoming high precision measurements of the Stochastic Gravitational-Wave Background (SGWB) energy density and the Cosmic Microwave Background (CMB) lensing convergence to mitigate the effect of shot noise
We study the cross-correlation between the astrophysical SGWB and the CMB lensing convergence in two different scenarios

Summary

Introduction

The direct detection of gravitational waves (GW) [1] achieved by the network of ground-based interferometers constituted by the Advanced Laser Interferometer Gravitatio nal-Wave Observatory (LIGO) [2], Advanced Virgo [3] and the Kamioka Gravitational Wave Detector (KAGRA) [4] has opened a new observational window on the Universe. The SGWB given by the incoherent superposition of GW events produced by merging stellar remnant compact binaries has raised significant interest among the scientific community [11–20]. This astrophysical SGWB is one of the dominant contributions in the frequency range explored by ground-based detectors (Hz-kHz) and is likely to be the first one to be detected. The SGWB anisotropies reflect the distribution of galaxies in the Universe and could constitute a new tracer of the Large-Scale Structure (LSS) For these reasons, the anisotropic SGWB has been extensively studied during the last few years, with relevant effort given to theoretical modeling [21–32], observational searches [33–36] and data analysis techniques [37–43]

Objectives

Methods

Results

Conclusion