Direct measurement of the distribution of dark matter with strongly lensed gravitational waves

TL;DR

This paper proposes using strongly lensed gravitational waves to measure dark matter's distribution and self-interaction properties, offering a new observational approach to constrain dark matter models.

Contribution

It introduces a novel method to probe dark matter self-interactions through gravitational wave lensing measurements, providing model-independent constraints.

Findings

Potential to constrain dark matter self-scattering cross-section with 10-1000 lensed GW events

Robust large-scale dark matter distribution measurements possible

More stringent limits than electromagnetic observations

Abstract

In this Letter, we present a new idea of probing the distribution of dark matter exhibiting elastic and velocity-independent self-interactions. These interactions might be revealed in multiple measurements of strongly lensed gravitational waves, which can be observationally explored to determine the strength of self-scatterings. Specifically, each individual galactic-scale strong-lensing system whose source is a coalescing compact binary emitting gravitational waves will provide a model-independent measurement of the shear viscosity of dark matter along the line of sight. These individual measurements could be a probe of large-scale distribution of dark matter and its properties. Our results indicate that with 10-1000 strongly lensed gravitational waves from ET and DECIGO, robust constraints on the large-scale distribution of self-interacting dark matter might be produced. More stringent limits on the dark matter scattering cross-section per unit mass ($\sigma_{\chi}/m_{\chi}$) relevant to galaxy and cluster scales are also expected, compared with the conservative estimates obtained in the electromagnetic domain. Finally, we discuss the effectiveness of our method in the context of self-interacting dark matter particle physics.