Stochastic background of gravitational waves generated by pre-galactic black holes

TL;DR

This paper models the stochastic gravitational wave background from pre-galactic black holes formed by early stars, predicting signals that could be detectable by future advanced interferometers, providing insights into early universe structure formation.

Contribution

It introduces a hierarchical structure formation model to estimate the gravitational wave background from pre-galactic black holes, linking star formation history with gravitational wave detectability.

Findings

Predicted gravitational wave signals are below current detector sensitivity but detectable by next-generation interferometers.

Correlation of advanced LIGO detectors could achieve high S/N ratios for signals from early star formation.

Future detectors like EGO could detect signals with lower efficiency, enabling astrophysical insights.

Abstract

In this work, we consider the stochastic background of gravitational waves (SBGWs) produced by pre-galactic stars, which form black holes in scenarios of structure formation. The calculation is performed in the framework of hierarchical structure formation using a Press-Schechter-like formalism. Our model reproduces the observed star formation rate at redshifts z < 6.5. The signal predicted in this work is below the sensitivity of the first generation of detectors but could be detectable by the next generation of ground-based interferometers. Specifically, correlating two coincident advanced LIGO detectors (LIGO III interferometers), the expected signal-to-noise-ratio (S/N) could be as high as 90 (10) for stars forming at redshift z ~ 20 with a Salpeter initial mass function with slope x=0.35 (1.35), and if the efficiency of generation of gravitational waves is close to the maximum value ~ 7 x 10^{-4}. However, the sensitivity of the future third generation of detectors as, for example, the European antenna EGO could be high enough to produce (S/N)}>3 same with efficiency ~ 2 x 10^{-5}. We also discuss what astrophysical information could be derived from a positive (or even negative) detection of the SBGWs investigated here.