Constraints on compact dark matter from gravitational wave microlensing

TL;DR

This paper uses gravitational wave microlensing observations, or the lack thereof, to place constraints on the fraction of dark matter composed of compact objects in the mass range of 100 to 100,000 solar masses, with future data expected to improve these limits.

Contribution

It provides the first constraints on compact dark matter in the specified mass range using gravitational wave microlensing data from LIGO and Virgo.

Findings

Less than 50-80% of dark matter in the mass range $10^2-10^5 M_\odot$ is in compact objects.

Current constraints are modest but will improve with future gravitational wave detections.

Non-observation of microlensing signatures limits the fraction of compact dark matter.

Abstract

If a significant fraction of dark matter is in the form of compact objects, they will cause microlensing effects in the gravitational wave (GW) signals observable by LIGO and Virgo. From the non-observation of microlensing signatures in the binary black hole events from the first two observing runs and the first half of the third observing run, we constrain the fraction of compact dark matter in the mass range $10^2-10^5~{M_\odot}$ to be less than $\simeq 50-80\%$ (details depend on the assumed source population properties and the Bayesian priors). These modest constraints will be significantly improved in the next few years with the expected detection of thousands of binary black hole events, providing a new avenue to probe the nature of dark matter.