Double Compact Objects III: Gravitational Wave Detection Rates

TL;DR

This paper predicts detection rates of double compact object mergers for second-generation gravitational-wave detectors, highlighting the impact of waveform modeling and the dominance of black hole mergers, especially from early low-metallicity environments.

Contribution

It provides updated detection rate predictions using advanced waveform models and cosmological evolution, emphasizing the significance of merger-ringdown signals and early Universe formation environments.

Findings

Merger-ringdown inclusion increases BH-BH detection rates by ~1.5 times.

BH-BH systems dominate detection rates over NS-NS and BH-NS.

Most detectable BH-BH mergers originate from low-metallicity early Universe environments.

Abstract

The unprecedented range of second-generation gravitational-wave (GW) observatories calls for refining the predictions of potential sources and detection rates. The coalescence of double compact objects (DCOs)---i.e., neutron star-neutron star (NS-NS), black hole-neutron star (BH-NS), and black hole-black hole (BH-BH) binary systems---is the most promising source of GWs for these detectors. We compute detection rates of coalescing DCOs in second-generation GW detectors using the latest models for their cosmological evolution, and implementing inspiral-merger-ringdown (IMR) gravitational waveform models in our signal-to-noise ratio calculations. We find that: (1) the inclusion of the merger/ringdown portion of the signal does not significantly affect rates for NS-NS and BH-NS systems, but it boosts rates by a factor $\sim 1.5$ for BH-BH systems; (2) in almost all of our models BH-BH systems yield by far the largest rates, followed by NS-NS and BH-NS systems, respectively, and (3) a majority of the detectable BH-BH systems were formed in the early Universe in low-metallicity environments. We make predictions for the distributions of detected binaries and discuss what the first GW detections will teach us about the astrophysics underlying binary formation and evolution.