Exploring compact binary populations with the Einstein Telescope

TL;DR

The paper demonstrates that the Einstein Telescope can detect and distinguish various compact binary populations across cosmic history, enabling detailed population and mass distribution studies of black hole and neutron star mergers.

Contribution

It provides a detailed analysis of the Einstein Telescope's capability to identify and differentiate compact binary populations from different stellar origins using a single detector.

Findings

ET can detect up to 10^6 binary black hole events annually.

Pop III binaries are distinguishable by mass and redshift separation.

Pop I+II and GCs can be distinguished with about 500 detections in roughly 1 hour.

Abstract

The Einstein Telescope (ET), a wide-band, future third generation gravitational wave detector, is expected to have detection rates of $\sim 10^5 - 10^6$ binary black hole (BBH) detections and $\sim 7 \times 10^4$ binary neutron star (BNS) detections in one year. The coalescence of compact binaries with a total mass of 20 - 100 $M_{\odot}$, typical of BH-BH or BH-NS binaries, will be visible up to redshift $z\approx 20$ and even higher, thus facilitating the understanding of the dark era of the Universe preceding the birth of the first stars. The ET will therefore be a crucial instrument for population studies. We analysed the compact binaries originating in stars from (i) Population (Pop) I+II, (ii) Pop III, and (iii) globular clusters (GCs), with the single ET instrument, using the ET-D design sensitivity for the analysis. We estimated the constraints on the chirp mass, redshift, and merger rate as function of redshift for these classes of compact object binaries. We conclude that the ET as a single instrument is capable of detecting and distinguishing different compact binary populations separated in chirp mass - redshift space. While compact binaries originating in stars from Pop III are clearly distinguishable, owing to the separation in chirp mass - redshift space, the other two populations, Pop I+II, and GCs, can be distinguished with just 500 detections, corresponding to an observation time of $\sim 1$ hr. The mass distribution characteristics of such different compact binary populations can also be estimated with the single ET instrument.