Formation of Massive Black Holes in Dense Star Clusters. I. Mass Segregation and Core Collapse

By S. Goswami, S. Umbreit, Matthew Bierbaum, F. Rasio. 2003

328 citations recorded by the source corpus.

We study the early dynamical evolution of young dense star clusters by using Monte Carlo simulations for systems with up to N = 107 stars. Rapid mass segregation of massive main-sequence stars and the development of the Spitzer instability can drive these systems to core collapse in a small fraction of the initial half-mass relaxation time. If the core-collapse time is less than the lifetime of the massive stars, all stars in the collapsing core may then undergo a runaway collision process leading to the formation of a massive black hole. Here we study in detail the first step in this process, up to the occurrence of core collapse. We have performed about 100 simulations for clusters with a wide variety of initial conditions, varying systematically the cluster density profile, stellar initial mass function (IMF), and number of stars. We also considered the effects of initial mass segregation and stellar evolution mass loss. Our results show that, for clusters with a moderate initial central concentration and any realistic IMF, the ratio of core-collapse time to initial half-mass relaxation time is typically ~0.1, in agreement with the value previously found by direct N-body simulations for much smaller systems. Models with even higher central concentration initially, or with initial mass segregation (from star formation) have even shorter core collapse times. Remarkably, we find that, for all realistic initial conditions, the mass of the collapsing core is always close to ~10-3 of the total cluster mass, very similar to the observed correlation between central black hole mass and total cluster mass in a variety of environments. We discuss the implications of our results for the formation of intermediate-mass black holes in globular clusters and super star clusters, ultraluminous X-ray sources, and seed black holes in proto-galactic nuclei.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/eb97cc8a4dcb1d10519dcec67bcaf5f6adf1cae0

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Citations in the corpus

COSMIC Variance in Binary Population Synthesis (2019, background): “The details of these merger products have important implications for blue straggler stars (e.g., Sandage 1953; Chatterjee et al. 2013) as well as the formation of massive BHs (e.g., Portegies Zwart & McMillan 2002; Gürkan et al. 2004; Kremer et al. 2019a).”
From Supermassive Black Holes to Dwarf Elliptical Nuclei: A Mass Continuum (2006, background): “2002; Gurkan et al. 2004).”
Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “e. There, they start to physically collide. The most massive star gains more and more mass and forms a runaway star that may collapse to form an intermediate-mass black hole (Freitag et al., 2006a,c, Gürkan et al., 2004, Portegies Zwart et al., 2004, Portegies Zwart and McMillan, 2000). Intermediate”
The Low End of the Supermassive Black Hole Mass Function: Constraining the Mass of a Nuclear Black Hole in NGC 205 via Stellar Kinematics (2005, background): “This time could be shortened somewhat if the central density rises inward of the resolution limit, or if the nucleus contains a range of stellar masses (e.g., Gürkan et al. 2004).”
Formation of supermassive black holes (2010, background): “…in principle form as a result of dynamical interactions in dense stellar systems is a long standing idea (Begelman and Rees, 1978; Ebisuzaki et al, 2001; Miller and Hamilton, 2002; Portegies Zwart and McMillan, 2002; Portegies Zwart et al, 2004; Freitag et al, 2006b,a; Gürkan et al, 2004, 2006).”
Massive Perturber-driven Interactions between Stars and a Massive Black Hole (2006, background): “However, such a massive IMBH is well beyond what is predicted by simulations of IMBH formation by runaway collisions (Gürkan et al. 2004; Gürkan & Rasio 2005), or anticipated by extrapolating theM/σ relation (Ferrarese & Merritt 2000; Gebhardt et al. 2000) to clusters.”
Binary Mergers and Growth of Black Holes in Dense Star Clusters (2005, background): “In our simulations we need to know the initial velocity dispersion of the BHs, O’LEARY ET AL.940 Vol. 637 BH. Numerical simulations suggest that themean kinetic energy of the dynamically decoupledmassive objects is only a few times larger than for other objects in the core (Gürkan et al. 2004).”
Massive black hole binaries from runaway collisions: the impact of metallicity (2016, background): “…Authors Several direct N-body simulations (Portegies Zwart & McMillan 2002; Moeckel & Clarke 2011) and Monte Carlo simulations (Gürkan et al. 2006; Goswami et al. 2012) investigating the runaway merger do not include prescriptions for stellar evolution, mass loss by stellar winds and SN…”
The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics, and Formation (2006, background): “However, as a helpful by-product, dynamical processes in such a hypothetical super-dense star cluster may then lead to the formation of a central, intermediate mass black hole (IMBH; PortegiesZwart & McMillian 2002; Gürkan et al, 2004).”
FORMATION OF THE FIRST NUCLEAR CLUSTERS AND MASSIVE BLACK HOLES AT HIGH REDSHIFT (2008, methodology): “The typical stellar masses are of order 105M⊙ and the typical half mass radii ∼ 1 pc. Eventually, a large fraction of these very dense clusters undergo core collapse before stars are able to complete stellar evolution and a VMS can form (e.g., Gürkan et al. 2004, Portegies Zwart et al. 2006).”