Wave-Optics Imprints of Dark Matter Subhalos on Strongly Lensed Gravitational Waves

TL;DR

This paper explores how wave-optics effects in strongly lensed gravitational waves can reveal dark matter substructure at subgalactic scales, using detailed diffraction calculations relevant for future LISA observations.

Contribution

It provides a comprehensive calculation of diffraction effects caused by dark matter subhalos on gravitational waves, demonstrating their detectability in LISA data within the cold dark matter framework.

Findings

Percent-level amplitude and phase distortions from subhalos in the $10^4$-$10^7 M_{\odot}$ range

Detectability of dark matter substructure signatures in high SNR LISA events

Dark matter subhalos produce observable wave-optics effects in gravitational wave signals

Abstract

Wave-optics effects in strongly lensed gravitational waves (GWs) provide a new interferometric probe of dark matter substructure. We compute the full diffraction integral for GWs propagating through statistically generated cold dark matter subhalo populations and quantify the resulting frequency-dependent amplification in the Laser Interferometer Space Antenna (LISA) band. We show that realistic galaxy-scale lenses generically produce percent-level amplitude and phase distortions in strongly magnified images, primarily induced by subhalos in the mass range $10^4$-$10^7\,M_{\odot}$. These signatures arise naturally within the standard cold dark matter paradigm and should be detectable in high signal-to-noise LISA events. Strongly lensed GWs thus offer a direct and complementary window on dark matter structure at subgalactic mass scales inaccessible to electromagnetic measurements.