Detecting a Stochastic Gravitational Wave Background in the presence of a Galactic Foreground and Instrument Noise

TL;DR

This paper demonstrates that a stochastic gravitational wave background can be detected in the millihertz band despite galactic foregrounds and instrument noise by modeling spectral components, using simulated LISA data.

Contribution

It extends previous work by showing detection feasibility with realistic modeling of signals and noise in LISA data, including galactic foregrounds and instrument noise.

Findings

Detection of stochastic background with Omega_gw as low as 2e-13 (6-link)

Detection of stochastic background with Omega_gw as low as 5e-13 (4-link)

Successful modeling of multiple signal components in simulated LISA data

Abstract

Detecting a stochastic gravitational wave background requires that we first understand and model any astrophysical foregrounds. In the millihertz frequency band, the predominate foreground signal will be from unresolved white dwarf binaries in the galaxy. We build on our previous work to show that a stochastic gravitational wave background can be detected in the presence of both instrument noise and a galactic confusion foreground. The key to our approach is accurately modeling the spectra for each of the various signal components. We simulate data for a gigameter Laser Interferometer Space Antenna (LISA) operating in the mHz frequency band detector operating with both 6- and 4-links. We obtain posterior distribution functions for the instrument noise parameters, the galaxy level and modulation parameters, and the stochastic background energy density. We find that we are able to detect a scale-invariant stochastic background with energy density as low as Omega_gw = 2e-13 for a 6-link interferometer and Omega_gw = 5e-13 for a 4-link interferometer with one year of data.