Detecting a gravitational-wave background with next-generation space interferometers

TL;DR

This paper evaluates the potential of future space-based interferometers to detect and analyze stochastic gravitational-wave backgrounds, focusing on sensitivity, foreground challenges, and anisotropy measurements around 0.1-10 Hz frequencies.

Contribution

It extends the theoretical framework for correlation analysis and assesses the sensitivity of upcoming missions like BBO and DECIGO for GWB detection.

Findings

Foreground point sources significantly impact detection sensitivity.

Minimum detectable amplitude could be as low as h^2 ogw = 10^{-15} to 10^{-16}.

Measurement of GWB anisotropies, such as dipole moments, is feasible with proper sensitivity.

Abstract

Future missions of gravitational-wave astronomy will be operated by space-based interferometers, covering very wide range of frequency. Search for stochastic gravitational-wave backgrounds (GWBs) is one of the main targets for such missions, and we here discuss the prospects for direct measurement of isotropic and anisotropic components of (primordial) GWBs around the frequency 0.1-10 Hz. After extending the theoretical basis for correlation analysis, we evaluate the sensitivity and the signal-to-noise ratio for the proposed future space interferometer missions, like Big-Bang Observer (BBO), Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO) and recently proposed Fabry-Perot type DECIGO. The astrophysical foregrounds which are expected at low frequency may be a big obstacle and significantly reduce the signal-to-noise ratio of GWBs. As a result, minimum detectable amplitude may reach h^2 \ogw = 10^{-15} \sim 10^{-16}, as long as foreground point sources are properly subtracted. Based on correlation analysis, we also discuss measurement of anisotropies of GWBs. As an example, the sensitivity level required for detecting the dipole moment of GWB induced by the proper motion of our local system is closely examined.