Merging black holes in young star clusters

By Ugo N Di Carlo, N. Giacobbo, Michela Mapelli, M. Pasquato, Mario Spera, Long Wang, F. Haardt. Monthly notices of the Royal Astronomical Society, 2019

179 citations recorded by the source corpus.

Searching for distinctive signatures, which characterize different formation channels of binary black holes (BBHs), is a crucial step towards the interpretation of current and future gravitational wave detections. Here, we investigate the demography of merging BBHs in young star clusters (SCs), which are the nursery of massive stars. We performed $4\times{} 10^3$ N-body simulations of SCs with metallicity $Z=0.002$, initial binary fraction $0.4$ and fractal initial conditions, to mimic the clumpiness of star forming regions. Our simulations include a novel population-synthesis approach based on the code MOBSE. We find that SC dynamics does not affect the merger rate significantly, but leaves a strong fingerprint on the properties of merging BBHs. More than 50 % of merging BBHs in young SCs form by dynamical exchanges in the first few Myr. Dynamically formed merging BBHs are significantly heavier than merging BBHs in isolated binaries: merging BBHs with total mass up to $\sim{}120$ M$_\odot$ form in young SCs, while the maximum total mass of merging BBHs in isolated binaries with the same metallicity is only $\sim{}70$ M$_\odot$. Merging BBHs born via dynamical exchanges tend to have smaller mass ratios than BBHs in isolated binaries. Furthermore, SC dynamics speeds up the merger: the delay time between star formation and coalescence is significantly shorter in young SCs. In our simulations, massive systems such as GW170729 form only via dynamical exchanges. Finally $\sim{}2$ % of merging BBHs in young SCs have mass in the pair-instability mass gap ($\sim{}60-120$ M$_\odot$). This represents a unique fingerprint of merging BBHs in SCs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2309d049b80b1c7832b759ff875f6a9d5c498f91

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Citations in the corpus

Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes (2017, background): “…Chatterjee et al. 2017; Mapelli 2016; Hurley et al. 2016; Rodriguez et al. 2016a; VanLandingham et al. 2016; Askar et al. 2017; Arca-Sedda & Capuzzo-Dolcetta 2019; Samsing 2018; Morawski et al. 2018; Banerjee 2018; Di Carlo et al. 2019; Zevin et al. 2019; Rodriguez et al. 2018; Perna et al. 2019).”
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): “VII.”
Constraints from Gravitational-wave Detections of Binary Black Hole Mergers on the 12C(α, γ)16O Rate (2020, background): “Black holes formed in dense stellar clusters or AGN disks (McKernan et al. 2018) can merge multiple times (Rodriguez et al. 2016; Stone et al. 2017; Di Carlo et al. 2019; Yang et al. 2019).”
Merging black hole binaries with the SEVN code (2018, background): “On the other hand, dynamical processes might easily lead to the formation of GW170729-like systems (Di Carlo et al. 2019).”