Spectral separation of the stochastic gravitational-wave background for LISA: galactic, cosmological and astrophysical backgrounds

TL;DR

This paper develops a spectral separation strategy for LISA to distinguish and analyze multiple stochastic gravitational-wave backgrounds, including galactic, astrophysical, and cosmological sources, using advanced data analysis methods.

Contribution

It introduces a novel spectral separation method for LISA data to simultaneously estimate multiple gravitational-wave backgrounds and determine detection limits for cosmological signals.

Findings

LISA can detect a cosmological background with energy density around 8 x 10^{-13}.

The proposed method effectively separates galactic and astrophysical backgrounds.

Simulation results validate the spectral separation strategy for future LISA observations.

Abstract

In its observation band, the Laser Interferometer Space Antenna (LISA) will simultaneously observe stochastic gravitational-wave background (SGWB) signals of different origins; orbitally modulated waveforms from galactic white dwarf binaries, a binary black hole produced background, and possibly a cosmologically produced SGWB. We simulate the emission of gravitational waves from galactic white dwarf binaries based on the Lamberts \cite{Lamberts} distributions and determine a complex waveform from the galactic foreground. We generate the modulated galactic signal detected by LISA due to its orbital motion, and present a data analysis strategy to address it. The Fisher Information and Markov Chain Monte Carlo methods give an estimate of the LISA noise and parameters for the different signal sources. We simultaneously estimate the galactic foreground, the astrophysical and cosmological backgrounds, and estimate detection limits for the future LISA observation of the SGWB in the spectral domain with the 3 LISA channels $ A $, $ E $ and $ T $. In the context of the expected astrophysical background and a galactic foreground, a cosmological background energy density of about $ \Omega_{GW,Cosmo} \approx 8 \times 10^{-13} $ could be detected by LISA with our spectral separation strategy.