Constraints on compact dark matter from the non-observation of gravitational-wave strong lensing

TL;DR

This paper uses the absence of gravitational wave strong lensing in LIGO-Virgo data to set upper limits on the fraction of dark matter composed of compact objects in the mass range 10^6-10^9 solar masses, with potential for tighter future constraints.

Contribution

It introduces a Bayesian method combined with astrophysical simulations to constrain compact dark matter, accounting for multiple lensing effects, which were previously neglected.

Findings

Constraints on dark matter fraction are less than 40-60%.

Multiple lensing effects can occur and slightly affect constraints.

Future data could significantly improve these constraints.

Abstract

We use the non-observation of strong lensing of gravitational waves (GWs) in the first three observation runs of LIGO-Virgo detectors to constrain the fraction of dark matter in the form of compact objects in the mass range $10^{6}-10^{9}~{\mathrm{M}_\odot}$. Using a Bayesian formalism supplemented by astrophysical simulations of strong lensing of GWs, we constrain the compact dark matter fraction to $\lesssim 0.4-0.6$ with currently available data and show that they may get significantly tighter in the future. We find that multiple lensing -- i.e., GWs getting deflected by multiple compact objects on their way to us -- is possible. By ignoring this, we underestimate the constraints by a few percent.