Gravitational waves from Population III binary black holes formed by dynamical capture

Understand

We use cosmological hydrodynamic simulations to study the gravitational wave (GW) signals from high-redshift binary black holes (BBHs) formed by dynamical capture (ex-situ formation channel).

• We in particular focus on BHs originating from the first generation of massive, metal-poor, so-called Population~III (Pop~III) stars.
• An alternative (in-situ) formation pathway arises in Pop~III binary stars, whose GW signature has been intensively studied.
• In our optimistic model, we predict a local GW event rate density for ex-situ BBHs (formed at z>4) of ~0.04 /(yr Gpc^3).