LIGO–Virgo–KAGRA's Oldest Black Holes: Probing Star Formation at Cosmic Noon With GWTC-3

Abstract

In their third observing run, the LIGO–Virgo–KAGRA gravitational-wave (GW) observatory was sensitive to binary black hole (BBH) mergers out to redshifts z merge ≈ 1. Because GWs are inefficient at shrinking the binary orbit, some of these BBH systems likely experienced long delay times τ between the formation of their progenitor stars at z form and their GW merger at z merge. In fact, the distribution of delay times predicted by isolated binary evolution resembles a power law p ( τ ) ∝ τ α τ with slope −1 ≲ α τ ≲ −0.35 and a minimum delay time of τ min = 10 Myr . We use these predicted delay time distributions to infer the formation redshifts of the ∼70 BBH events reported in the third GW transient catalog GWTC-3 and the formation rate of BBH progenitors. For our default α τ = –1 delay time distribution, we find that GWTC-3 contains at least one system (with 90% credibility) that formed earlier than z form > 4.4. Comparing our inferred BBH progenitor formation rate to the star formation rate, we find that at z form = 4, the number of BBH progenitor systems formed per stellar mass was 6.4 − 5.5 + 9.4 × 10 − 6 M ⊙ − 1 and this yield dropped to 0.134 − 0.127 + 1.6 × 10 − 6 M ⊙ − 1 by z form = 0. We discuss implications of this measurement for the cosmic metallicity evolution, finding that for typical assumptions about the metallicity dependence of the BBH yield, the average metallicity at z form = 4 was 〈 log 10 ( Z / Z ⊙ ) 〉 = − 0.3 − 0.4 + 0.3 , although the inferred metallicity can vary by a factor of ≈3 for different assumptions about the BBH yield. Our results highlight the promise of current GW observatories to probe high-redshift star formation.

The Metallicity Dependence and Evolutionary Times of Merging Binary Black Holes: Combined Constraints from Individual Gravitational-wave Detections and the Stochastic Background

“…The measurement of these parameters could shed light on the different binary formation channels, because each of these predicts different values of the spectral index κ. For example, the value of κ is expected to be −1 in the classical field formation scenario (Dominik et al 2012(Dominik et al , 2013Fishbach & van Son 2023).…”

“…Current gravitational-wave detectors, however, are limited in their ability to probe high-redshift binary black hole merger events. For example, current catalogs provide meaningful constraints on the merger rate only to z  1 (Abbott et al 2023a;Callister & Farr 2024), although the formation rate can be probed out to z ∼ 4 for population synthesis-motivated assumptions about the time-delay distribution (Fishbach & van Son 2023). Even with the future Advanced LIGO A+ sensitivity (Barsotti et al 2018), the redshifts that will be probed by individual compact binary detections will likely remain below z ∼ 3, thus suggesting that the high-redshift investigation of the binary black hole merger rate will remain challenging, at least until the era of next-generation instruments like the Einstein Telescope and Cosmic Explorer (Vitale et al 2019;Evans et al 2021;Borhanian & Sathyaprakash 2022).…”

Spin Doctors: How to Diagnose a Hierarchical Merger Origin

“…In addition to spins, trends in the mass spectrum (e.g., Stevenson et al 2015;Zevin et al 2017;Fishbach et al 2021;Belczynski et al 2022;Mahapatra et al 2022;Abbott et al 2023b;van Son et al 2023), redshift evolution (e.g., Rodriguez & Loeb 2018;van Son et al 2022;Fishbach & van Son 2023), orbital eccentricity (e.g., Zevin et al 2021b), and correlations between BBH parameters (e.g., Callister et al 2021;Adamcewicz & Thrane 2022;Biscoveanu et al 2022;Broekgaarden et al 2022;McKernan et al 2022;Tiwari 2022; Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.…”