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

Abstract

Future missions of gravitational-wave astronomy will be operated by\nspace-based interferometers, covering very wide range of frequency. Search for\nstochastic gravitational-wave backgrounds (GWBs) is one of the main targets for\nsuch missions, and we here discuss the prospects for direct measurement of\nisotropic and anisotropic components of (primordial) GWBs around the frequency\n0.1-10 Hz. After extending the theoretical basis for correlation analysis, we\nevaluate the sensitivity and the signal-to-noise ratio for the proposed future\nspace interferometer missions, like Big-Bang Observer (BBO), Deci-Hertz\nInterferometer Gravitational-wave Observer (DECIGO) and recently proposed\nFabry-Perot type DECIGO. The astrophysical foregrounds which are expected at\nlow frequency may be a big obstacle and significantly reduce the\nsignal-to-noise ratio of GWBs. As a result, minimum detectable amplitude may\nreach h^2 \\ogw = 10^{-15} \\sim 10^{-16}, as long as foreground point sources\nare properly subtracted. Based on correlation analysis, we also discuss\nmeasurement of anisotropies of GWBs. As an example, the sensitivity level\nrequired for detecting the dipole moment of GWB induced by the proper motion of\nour local system is closely examined.\n