The Runaway Growth of Intermediate-Mass Black Holes in Dense Star Clusters

By S. P. Portegies Zwart, S. McMillan. 2002

531 citations recorded by the source corpus.

We study the growth rate of stars via stellar collisions in dense star clusters, calibrating our analytic calculations with direct N-body simulations of up to 65,536 stars, performed on the GRAPE family of special-purpose computers. We find that star clusters with initial half-mass relaxation times ≲25 Myr are dominated by stellar collisions, the first collisions occurring at or near the point of core collapse, which is driven by the segregation of the most massive stars to the cluster center, where they end up in hard binaries. The majority of collisions occur with the same star, resulting in the runaway growth of a supermassive object. This object can grow up to ~0.1% of the mass of the entire star cluster and could manifest itself as an intermediate-mass black hole (IMBH). The phase of runaway growth lasts until mass loss by stellar evolution arrests core collapse. Star clusters older than about 5 Myr and with present-day half-mass relaxation times ≲100 Myr are expected to contain an IMBH.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ee97f6c1eb66faa8c114485c9bbb616f282b0f02

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Citations in the corpus

N-body modelling of globular clusters: masses, mass-to-light ratios and intermediate-mass black holes (2016, background): “The high stellar densities in globular cluster could also give rise to the creation of intermediate-mass black holes (Portegies Zwart & McMillan 2002; Portegies Zwart et al. 2004; Giersz et al. 2015), which might be the progenitors of supermassive black holes in Galactic centers.”
Formation of supermassive black holes (2010, background): “If mass segregation sets in before the more massive stars evolve out of the main sequence (∼ 3 Myr), then a sub-system decoupled from the rest of the cluster can form, where star-star collisions can take place in a runaway fashion that ultimately leads to the growth of a VMS (Portegies Zwart et al, ”
Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling (2002, background): “Studies of such scenarios have gained much interest lately (Ebisuzaki et al. 2001; Miller & Hamilton 2002; Mouri & Taniguchi 2002; Portegies Zwart & McMillan 2002) after the discovery of ultraluminous X-ray objects in external galaxies (e.g., Colbert & Mushotzky 1999).”
Merging black holes in young star clusters (2019, background): “Despite this, most studies of BH dynamics neglect young SCs and star forming regions, with few exceptions (Portegies Zwart & McMillan 2002; Banerjee et al. 2010; Ziosi et al. 2014; Goswami et al. 2014; Mapelli 2016; Banerjee 2017, 2018; Fujii et al. 2017; Rastello et al. 2018).”
Formation of Massive Black Holes in Dense Star Clusters. I. Mass Segregation and Core Collapse (2003, background): “This is also supported by the results of direct N -body simulations showing that, in smaller systems containing N 10 4 single stars, collisions indeed occur predominantly through the interactions of three-body binaries formed at core collapse (Portegies Zwart & McMillan 2002).”
Observational evidence for intermediate-mass black holes (2017, background): “…al. 2015, 2017; Mezcua et al. 2016); in nearby globular clusters, as stellar clusters are one of the sites of possible IMBH formation (e.g., Portegies Zwart & McMillan 2002; Portegies Zwart et al. 2004; Freitag et al. 2006; Kızıltan et al. 2017); or in the form of off-nuclear ultraluminous X-ray…”
The Need for a Second Black Hole at the Galactic Center (2003, background): “…it has been argued that such black holes form generically in dense, young stellar clusters as a result of the segregation of massive stars to the cluster center (Spitzer 1969) followed by the runaway merging in stellar collisions (Portegies Zwart & McMillan 2002; Rasio, Freitag & Gürkan 2003).”
The Ultraluminous State (2009, background): “…endpoint of a recent single stellar evolution, but require more exotic origins such as stellar mergers in a young super star cluster (e.g. Portegies-Zwart & McMillan 2002) or formation from primordial Population III stars in the high-redshift Universe (Madau & Rees 2001). c© 2009 RAS, MNRAS000,…”
NEW LIMITS ON AN INTERMEDIATE-MASS BLACK HOLE IN OMEGA CENTAURI. I. HUBBLE SPACE TELESCOPE PHOTOMETRY AND PROPER MOTIONS (2009, background): “Plausible formation scenarios exist to form such IMBHs in the centers of globular clusters from realistic initial conditions (Portegies Zwart & McMillan 2002).”
The mass spectrum of compact remnants from the parsec stellar evolution tracks (2015, background): “Furthermore, extreme dynamical processes, such as repeated mergers of compact remnants (Miller & Hamilton 2002) and the runaway merger of massive objects in star clusters (Portegies Zwart & McMillan 2002), can lead to the formation of intermediate-mass BHs (i.e. BHs with mass 10 2 –10 5 M (cid:4) ).”
Black-hole binaries, gravitational waves, and numerical relativity (2010, background): “IMBHs may form as the result of multiple mergers of smaller objects in the centers of dense stellar clusters in the present Universe (Miller and Colbert, 2004; Portegies Zwart and McMillan, 2002), assuming mass loss from stellar winds is not significant (Glebbeek et al., 2009).”
Ultraluminous X-ray sources in the Chandra and XMM-Newton era (2011, background): “Numerical simulations suggest that such a process may result in the formation of a huge star, which may subsequently collapse into an IMBH (Portegies Zwart & McMillan 2002; Gürkan et al. 2004; Portegies Zwart et al. 2004; Vanbeveren et al. 2009).”
Formation of Supermassive Black Hole Seeds (2016, background): “The mass of a seed black hole forming from the core collapse of a cluster can be estimated as follows (Portegies Zwart & McMillan 2002), MBH = m∗ + 4× 10 −3fcMc0γ ln ΛC .”
Black Holes in Pseudobulges and Spheroidals: A Change in the Black Hole-Bulge Scaling Relations at Low Mass (2008, background): “2005, ApJ, 632, 799 Pizzella, A., Corsini, E. M., Dalla Bontà, E., Sarzi, M., Coccato, L., & Bertola, F. 2005, ApJ, 631, 785 Portegies Zwart, S. F., & McMillan, S. L. W. 2002, ApJ, 576, 899 Rhodes, J. D., Massey, R., Albert, J., Taylor, J. E., Koekemoer, A. M., & Leauthaud,A. 2006, inThe 2005HSTCal”
The physics of star formation (2003, background): “In sufficiently dense young clusters, the runaway merging of already formed massive stars might also result in the formation of very massive stars and eventually black holes at the cluster center (Portegies Zwart and McMillan 2002).”
The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics, and Formation (2006, background): “First, such a massive black hole is not easy to form as a result of core collapse even in a very massive (106M⊙) in-spiraling cluster, as core collapse typically creates a central concentration no more massive than≃ 10−3 of the original cluster mass (Portegies Zwart & McMillan 2002).”