Unveiling Hidden Signals: Leveraging Galaxy Distributions to Model the Astrophysical Foreground in Simulated LISA Data

Gravitational waves have provided a new lens to view the universe beyond traditional electromagnetic methods. The upcoming space-based gravitational wave mission, Laser Interferometer Space Antenna (LISA), will give us the first glimpse of the sky in mHz gravitational waves, a waveband that contains a rich variety of sources. These include signals from binary black hole (BBH) mergers, binary neutron star systems, and weaker signals from inflation, cosmic strings, and defects in space topology. To detect any cosmological gravitational wave background (GWB), we need to understand and model the global astrophysical foreground. In this work, we aim to investigate whether the spatial distribution of galaxies can serve as a proxy for the distribution of the BBH mergers as the former can be observed and the latter cannot. We begin by comparing the two-point correlation function of the BBH mergers to that of galaxies. If the spatial distribution of galaxies is indeed a suitable representation of the BBH merger clustering, we can then determine how well a simulated map of the LISA BBH mergers can determine the astrophysical foreground. Our data was created using the cosmological hydrodynamic IllustrisTNG simulation with a cubic volume of 100Mpc at redshift zero. This research presents preliminary results on the clustering of the BBH mergers versus the galaxy clustering. Through the reapplication of the two-point correlation function to the concluding simulated LISA map and its subsequent comparison with the initially simulated BBH merger data, we can effectively evaluate the potential for eliminating more dominant signals from the GWB, leaving behind weaker cosmological transmissions.