Templated Anisotropic Analyses of the LISA Galactic Foreground

TL;DR

This paper introduces a Bayesian method to analyze the anisotropic Galactic foreground in LISA data, enabling accurate characterization of unresolved white dwarf binaries and their spatial distribution within the Milky Way.

Contribution

It presents a novel Bayesian framework that models the anisotropic Galactic foreground using astrophysically-motivated templates, linking observed modulation to spatial distribution.

Findings

Method accurately recovers the foreground spectrum in simulated data.

Approach effectively accounts for LISA instrumental noise.

Validates the connection between time-modulation and spatial distribution.

Abstract

The Laser Interferometer Space Antenna (LISA) will feature a prominent anisotropic astrophysical stochastic gravitational wave signal, arising from the tens of millions of unresolved mHz white dwarf binaries in the Milky Way: the Galactic foreground. While proper characterization of the Galactic foreground as a noise source will be crucial for every LISA science goal, it is extremely scientifically interesting in its own right, comprising -- along with $\sim10^4$ resolvable white dwarf binaries -- a complete sample of every mHz white dwarf binary in our Galaxy. We present a novel Bayesian analysis of the LISA Galactic foreground that directly treats its anisotropy via astrophysically-motivated templates, allowing for a direct connection between the observed time-modulation of the foreground amplitude and the underlying spatial distribution of the Milky Way. We validate the efficacy of this approach via simulated data and show that it is able to accurately recover the foreground spectrum in the presence of LISA instrumental noise.