Are LIGO's Black Holes Made from Smaller Black Holes?

By Maya Fishbach, D. Holz, B. Farr. 2017

240 citations recorded by the source corpus.

One proposed formation channel for stellar mass black holes (BHs) is through hierarchical mergers of smaller BHs. Repeated mergers between comparable mass BHs leave an imprint on the spin of the resulting BH since the final BH spin is largely determined by the orbital angular momentum of the binary. We find that for stellar mass BHs forming hierarchically the distribution of spin magnitudes is universal, with a peak at and little support below . We show that the spin distribution is robust against changes to the mass ratio of the merging binaries, the initial spin distribution of the first generation of BHs, and the number of merger generations. While we assume an isotropic distribution of initial spin directions, spins that are preferentially aligned or antialigned do not qualitatively change our results. We also consider a “cluster catastrophe” model for BH formation in which we allow for mergers of arbitrary mass ratios and show that this scenario predicts a unique spin distribution that is similar to the universal distribution derived for major majors. We explore the ability of spin measurements from ground-based gravitational-wave (GW) detectors to constrain hierarchical merger scenarios. We apply a hierarchical Bayesian mixture model to mock GW data and argue that the fraction of BHs that formed through hierarchical mergers will be constrained with LIGO binary black hole detections, while with detections we could falsify a model in which all component BHs form hierarchically.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2afb6e9f06f0098a13e2ec737e3d5876c608c3a8

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Citations in the corpus

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs (2018, background): “[224] M.”
Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections (2018, background): “After the first few mergers, we expect χ ≈ 0.7 (Gerosa & Berti 2017; Fishbach et al. 2017).”
Constraints from Gravitational-wave Detections of Binary Black Hole Mergers on the 12C(α, γ)16O Rate (2020, background): “If they are distinguishable from mergers due to isolated binary evolution, for instance via their spin (Fishbach et al. 2017; Gerosa & Berti 2017; Bouffanais et al. 2019; Arca Sedda et al. 2020), then they could be removed from the population used to infer the a gC , O12 16( ) rate.”
Constraining Stellar-mass Black Hole Mergers in AGN Disks Detectable with LIGO (2017, background): “Our estimates of f±align suggest that a larger population of mergers will be required to test this channel in population spin studies than estimated by Fishbach et al. (2017) and Gerosa & Berti (2017).”
GW190521: Orbital Eccentricity and Signatures of Dynamical Formation in a Binary Black Hole Merger Signal (2020, background): “…eccentricity of field mergers can be increased by Kozai–Lidov resonance (Kozai 1962; Lidov 1962) during three-body (Antonini et al. 2017; Fishbach et al. 2017; Silsbee & Tremaine 2017; Rodriguez & Antonini 2018; Liu et al. 2019; Fragione & Kocsis 2020) and four-body (Fragione & Kocsis…”
Eccentric Black Hole Mergers in Dense Star Clusters: The Role of Binary–Binary Encounters (2018, background): “…have utility once dozens to hundreds of observations are made (Stevenson et al. 2015; Mandel et al. 2016; Zevin et al. 2017) or if second generation BH mergers are found with masses in the putative pair instability upper mass gap (O’Leary et al. 2016; Fishbach et al. 2017; Rodriguez et al. 2018b).”
Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes (2017, background): “It seems unlikely that isolated binaries can fill this gap, but repeated BH-BH mergers in dense environments could produce such heavy BHs, and it is expected that they would have moderately high spins aspin ≈ 0.7 (Gerosa & Berti 2017; Fishbach et al. 2017).”
Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo (2018, background): “Several studies have noted that population features(Mandel & O’Shaughnessy 2010; Stevenson et al. 2015, 2017a; Farr et al. 2017, 2018; Fishbach et al. 2017; Fishbach & Holz 2017; Gerosa & Berti 2017; Kovetz et al. 2017; Talbot & Thrane 2017, 2018; Zevin et al. 2017; Barrett et al. 2018; Gerosa et…”
Most Black Holes Are Born Very Slowly Rotating (2019, background): “However, a caveat is the population of rapidly rotating (a ∼ 0.7) BH primaries expected for second generation cluster mergers (Antonini & Rasio 2016; Fishbach et al. 2017; Gerosa & Berti 2017; Rodriguez et al. 2018).”
GW231123: A Binary Black Hole Merger with Total Mass 190–265 M⊙ (2025, unknown): “As seen in Figure 4, the spins inferred from GW231123 may be even larger than typically predicted from hierarchical BH mergers (Gerosa & Berti 2017; Fishbach et al. 2017), although the expected distribution for sources retained in their host environments may accommodate a wider range of spins…”
Where Are LIGO’s Big Black Holes? (2017, background): “The BBH spin distribution will provide further constraints on the existence of these subpopulations and will allow us to measure the fraction of BBHs that formed through previous mergers (Fishbach et al. 2017; Gerosa & Berti 2017).”
Hierarchical analysis of gravitational-wave measurements of binary black hole spin–orbit misalignments (2017, background): “Optimal hierarchical modelling should fold in all available information, including component masses (cf. Ro- MNRAS 000, 1–12 (2017) driguez et al. 2016) and spin magnitudes (cf. Gerosa & Berti 2017; Fishbach et al. 2017), into a single analysis.”
The evolution of primordial black holes and their final observable spins (2020, result): “They are therefore similar to those computed in other astrophysical scenarios [28, 29, 63].”
GWTC-2.1: Deep extended catalog of compact binary coalescences observed by LIGO and Virgo during the first half of the third observing run (2021, unknown): “This might suggest that the primary component of GW190403_051519 is a second-generation BH, which is also consistent with its large mass [208,209,217,253,254].”