Searching for Anisotropic Stochastic Gravitational-wave Backgrounds with Constellations of Space-based Interferometers

Abstract

Many recent works have shown that the angular resolution of ground-based detectors is too poor to characterize the anisotropies of the stochastic gravitational-wave background (SGWB). For this reason, we asked ourselves if a constellation of space-based instruments could be more suitable. We consider the Laser Interferometer Space Antenna (LISA), a constellation of multiple LISA-like clusters, and the Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO). Specifically, we test whether these detector constellations can probe the anisotropies of the SGWB. For this scope, we considered the SGWB produced by two astrophysical sources: merging compact binaries, and a recently proposed scenario for massive black hole seed formation through multiple mergers of stellar remnants. We find that measuring the angular power spectrum of the SGWB anisotropies is almost unattainable. However, it turns out that it could be possible to probe the SGWB anisotropies through cross-correlation with the cosmic microwave background (CMB) fluctuations. In particular, we find that a constellation of two LISA-like detectors and CMB-S4 can marginally constrain the cross-correlation between the CMB lensing convergence and the SGWB produced by the black hole seed formation process. Moreover, we find that DECIGO can probe the cross-correlation between the CMB lensing and the SGWB from merging compact binaries.

Primordial non-Gaussianity fNLand anisotropies in scalar-induced gravitational waves

“…A detector network could measure the angular power spectrum for multipoles ℓ = 1 − 19 with a significantly higher sensitivity than an individual cluster [135]. This result may also bring new insights to potential developments of the LISA-Taiji network [139,140].…”

“…We take σ = 1/3, 1/2, 1 from left to right panels. The anticipated angular power spectra versus the noise angular power spectra of LISA (at 1 mHz band, left panel) [135] and DECIGO (at 0.1 Hz band, right panel) [135]. The shaded regions stand for the cosmic-variance limits (68% confidence level).…”

Angular bispectrum and trispectrum of scalar-induced gravitational waves: all contributions from primordial non-Gaussianity f NL and g NL

“…vanishes if all the four multipoles are not equal, so that the angular averaged trispectrum is just the connected part T c ℓ 1 ℓ 2 ℓ 3 ℓ 4 (L, ν). Due to limitations in the angular resolutions of ongoing and planned GW detectors [37,120,[133][134][135][136][137][138][139], we consider only the low multipoles ℓ in our present work. However, it is straightforward to generalize our analysis to higher multipoles ℓ if needed.…”

Constellation attitude tracking control of the space gravitational wave observatory under configuration disturbances

“…As the most mature scheme, a long baseline laser ranging system consisting of multiple spacecrafts in predefined optimized orbits [2,3] is used to conduct scientific measurement. At present, the space gravitational wave detection programs of various countries are in close planning and promotion, such as LISA [4], TaiJi [5], TianQin [6], DICEGO [7]. In order to be able to measure the spatial and temporal distortions due to the passage of Gravitational Waves (GW) through the laser optical path, i.e., the change in the optical path arm length, the measurement accuracy needs to reach picometer level [8,9].…”