Stellar-mass black holes in young massive and open stellar clusters – IV. Updated stellar-evolutionary and black hole spin models and comparisons with the LIGO-Virgo O1/O2 merger-event data

Abstract

I present a set of long-term, direct, relativistic many-body computations of model dense stellar clusters with up-to-date stellar-evolutionary, supernova (SN), and remnant natal-kick models, including pair instability and pulsation pair instability supernova (PSN and PPSN), using an updated version of ${\tt NBODY7}$ N-body simulation program. The N-body model also includes stellar evolution-based natal spins of BHs and treatments of binary black hole (BBH) mergers based on numerical relativity. These, for the first time in a direct N-body simulation, allow for second-generation BBH mergers. The set of 65 evolutionary models have initial masses 104M⊙ − 105M⊙, sizes 1 pc-3 pc, metallicity 0.0001 − 0.02, with the massive stars in primordial binaries and they represent young massive clusters (YMC) and moderately massive open clusters (OC). Such models produce dynamically-paired BBH mergers that agree well with the observed masses, mass ratios, effective spin parameters, and final spins of the LVC O1/O2 merger events, provided BHs are born with low or no spin but spin up after undergoing a BBH merger or matter accretion onto it. In particular, the distinctly higher mass, effective spin parameter, and final spin of GW170729 merger event is naturally reproduced, as also the mass asymmetry of the O3 event GW190412. The computed models produce massive, ∼100M⊙ BBH mergers with primary mass within the ‘PSN gap’ and also yield mergers involving remnants in the ‘mass gap’. They also suggest that YMCs and OCs produce persistent, Local-Universe GW sources detectable by LISA. Such clusters are also capable of producing eccentric LIGO-Virgo mergers.

Black Hole Mergers from Hierarchical Triples in Dense Star Clusters

“…We also find that, since GW radiation is efficient in reducing the eccentricity of merging binaries, sub-hertz detectors such as the proposed DECIGO detector (Kawamura et al 2011) will be crucial to understand the contribution of GCs to the merger rate (see also . Note, that due to limitations of the CMC code, we are not including effects from weak secular interactions that otherwise have been shown to both increase the BBH merger rate and give rise to dynamics similar to those of eKL interactions, including orbital spin flips and eccentricity excitations , 2020Samsing et al 2019).…”

“…There have been many proposed formation channels, both in dense stellar environments and in isolation. These include isolated binary stellar evolution of two massive stars either through common-envelope evolution (Dominik et al 2012(Dominik et al , 2013Belczynski et al 2016aBelczynski et al , 2016bSpera et al 2019), chemically homogeneous evolution of close binaries (de Mink & Mandel 2016; Mandel & de Mink 2016), or catalyzed by flyby perturbations in the field (Michaely & Perets 2019, 2020, or dynamical assembly in dense stellar environments, including young and open star clusters (Banerjee 2017(Banerjee , 2018a(Banerjee , 2018b(Banerjee , 2020Di Carlo et al 2019;Santoliquido et al 2020) Hamers et al 2018;Hoang et al 2018;Fragione et al 2019a;Rasskazov & Kocsis 2019;Stephan et al 2019), and in active galactic nucleus (AGN) (Bartos et al 2017;Stone et al 2017;Tagawa et al 2018Tagawa et al , 2020aTagawa et al , 2020bMcKernan et al 2020). Another proposed scenario involves primordial BHs merging in the halos of galaxies (e.g., Bird et al 2016).…”

Fast Optical Transients from Stellar-mass Black Hole Tidal Disruption Events in Young Star Clusters

“…Ultimately (depending on the host cluster's escape velocity), these binary BHs (BBHs) are either dynamically ejected from their host cluster through gravitational recoil or merge inside their host cluster through GW inspiral. Recent studies have shown that YSCs (e.g., Ziosi et al 2014;Di Carlo et al 2019a;Banerjee 2021) and old GCs (e.g., Rodriguez & Loeb 2018;Antonini & Gieles 2020;Kremer et al 2020b) may contribute comparably to the overall BBH merger rate.…”

Mass and Rate of Hierarchical Black Hole Mergers in Young, Globular and Nuclear Star Clusters

“…Several channels can lead to the formation of binary black holes (BBHs): Pairing of primordial black holes (e.g., [12][13][14]), binary star evolution through common envelope (e.g., ) or via homogeneous mixing (e.g., [39][40][41][42]), dynamical processes in triples (e.g., [43][44][45][46][47]), young/open star clusters (YSCs, e.g., [48][49][50][51][52][53][54][55][56][57][58]), globular clusters (GCs, e.g., [59][60][61][62][63][64][65][66][67][68]), nuclear star clusters (NSCs, e.g., [69][70][71][72][73][74][75][76][77]) and AGN disks (e.g., [78][79][80][81][82][83]).…”