Discriminating scalar ultralight dark matter from quasi-monochromatic gravitational waves in LISA

TL;DR

This paper investigates whether LISA can distinguish scalar ultralight dark matter signals from gravitational wave signals using Bayesian analysis and realistic orbital data.

Contribution

It provides a numerical study demonstrating LISA's capability to differentiate ULDM signals from gravitational waves.

Findings

LISA can successfully discriminate between ULDM and GW signals.

Bayesian methods are effective in identifying the nature of the signals.

Realistic orbital simulations support the feasibility of detection.

Abstract

A scalar ultralight dark matter (ULDM) candidate would induce oscillatory motion of freely falling test masses via its coupling to Standard Model fields. Such oscillations would create an observable Doppler shift of light exchanged between the test masses, and in particular would be visible in space-based gravitational waves (GW) detectors, such as LISA. While this kind of detection has been proposed multiple times in the recent years, we numerically investigate if it is possible to extract a scalar ULDM signal in a space-based GW detector, and in particular how to differentiate such a signal from a GW signal. Using one year of realistic orbits for the LISA spacecrafts and Bayesian methods, we find that LISA will indeed be able to discriminate between the two signals.