Coalescence Rate of Supermassive Black Hole Binaries Derived from Cosmological Simulations: Detection Rates for LISA and ET

TL;DR

This paper uses cosmological simulations to estimate the coalescence rates of supermassive black holes and predicts gravitational wave detection rates for LISA and Einstein telescopes, aiding understanding of black hole origins.

Contribution

It provides the first detailed coalescence rate estimates from cosmological simulations and predicts gravitational wave detection rates for upcoming observatories.

Findings

LISA may detect about 15 events per year with SNR 10.

Einstein telescope could observe one event every 14 months to 4 years with SNR 5.

Most detectable signals occur in the 4-20 mHz frequency range.

Abstract

The coalescence history of massive black holes has been derived from cosmological simulations, in which the evolution of those objects and that of the host galaxies are followed in a consistent way. The present study indicates that supermassive black holes having masses greater than $\sim 10^{9} M_{\odot}$ underwent up to 500 merger events along their history. The derived coalescence rate per comoving volume and per mass interval permitted to obtain an estimate of the expected detection rate distribution of gravitational wave signals ("ring-down") along frequencies accessible by the planned interferometers either in space (LISA) or in the ground (Einstein). For LISA, in its original configuration, a total detection rate of about $15 yr^{-1}$ is predicted for events having a signal-to-noise ratio equal to 10, expected to occur mainly in the frequency range $4-9 mHz$. For the Einstein gravitational wave telescope, one event each 14 months down to one event each 4 years is expected with a signal-to-noise ratio of 5, occurring mainly in the frequency interval $10-20 Hz$. The detection of these gravitational signals and their distribution in frequency would be in the future an important tool able to discriminate among different scenarios explaining the origin of supermassive black holes.