Cross-correlating Astrophysical and Cosmological Gravitational Wave Backgrounds with the Cosmic Microwave Background

TL;DR

This paper investigates how future gravitational wave detectors can cross-correlate astrophysical and cosmological SGWBs with CMB anisotropies, enabling new insights into the universe's structure and origins.

Contribution

It introduces the concept of cross-correlating SGWBs with CMB anisotropies and presents a novel constrained realization method to reconstruct SGWB maps from CMB data.

Findings

Future GW detectors can measure SGWB-CMB cross-correlations.

Constrained realization maps can reconstruct SGWB from CMB data.

The method enhances understanding of the universe's structure.

Abstract

General Relativity provides us with an extremely powerful tool to extract at the same time astrophysical and cosmological information from the Stochastic Gravitational Wave Backgrounds (SGWBs): the cross-correlation with other cosmological tracers, since their anisotropies share a common origin and the same perturbed geodesics. In this letter we explore the cross-correlation of the cosmological and astrophysical SGWBs with Cosmic Microwave Background (CMB) anisotropies, showing that future GW detectors, such as LISA or BBO, have the ability to measure such cross-correlation signals. We also present, as a new tool in this context, constrained realization maps of the SGWBs extracted from the high-resolution CMB {\it Planck} maps. This technique allows, in the low-noise regime, to faithfully reconstruct the expected SGWB map by starting from CMB measurements.