Dependence of Gravitational Wave Transient Rates on Cosmic Star Formation and Metallicity Evolution History

TL;DR

This paper investigates how uncertainties in cosmic star formation and metallicity evolution influence the predicted rates of gravitational wave events from compact binary mergers, highlighting the dominant role of metallicity evolution.

Contribution

It quantifies the impact of different astrophysical uncertainties on gravitational wave event rate predictions, emphasizing the importance of metallicity evolution.

Findings

Metallicity evolution has the strongest effect on GW rate predictions.

Varying neutron-star kick velocities significantly affects double neutron-star merger rates.

Considering all merger types can help break degeneracies in rate predictions.

Abstract

We compare the impacts of uncertainties in both binary population synthesis models and the cosmic star formation history on the predicted rates of Gravitational Wave compact binary merger (GW) events. These uncertainties cause the predicted rates of GW events to vary by up to an order of magnitude. Varying the volume-averaged star formation rate density history of the Universe causes the weakest change to our predictions, while varying the metallicity evolution has the strongest effect. Double neutron-star merger rates are more sensitive to assumed neutron-star kick velocity than the cosmic star formation history. Varying certain parameters affects merger rates in different ways depending on the mass of the merging compact objects; thus some of the degeneracy may be broken by looking at all the event rates rather than restricting ourselves to one class of mergers.