Probing the Dark Matter density with gravitational waves from super-massive binary black holes

TL;DR

This paper proposes using gravitational wave measurements from supermassive black hole binaries to constrain dark matter density profiles, leveraging the impact of dark matter friction on the gravitational wave spectrum at nanohertz frequencies.

Contribution

It introduces a novel method to derive bounds on dark matter density using gravitational wave spectrum suppression caused by dark matter friction.

Findings

Dark matter friction can suppress gravitational wave spectrum at nHz frequencies.

Robust bounds on dark matter density can be derived from gravitational wave data.

Potential to probe dark matter particle physics effects through gravitational wave tomography.

Abstract

Supermassive black hole binaries source gravitational waves measured by Pulsar Timing Arrays. The frequency spectrum of this stochastic background is predicted more precisely than its amplitude. We argue that Dark Matter friction can suppress the spectrum around nHz frequencies, where it is measured, allowing to derive robust and significant bounds on the Dark Matter density, which, in turn, controls indirect detection signals from galactic centers. A precise spectrum of gravitational waves would translate in a tomography of the DM density profile, potentially probing DM particle-physics effects that induce a characteristic DM density profile, such as DM annihilations or de Broglie wavelength.