Intermediate-mass black holes from stellar mergers in young star clusters

Carlo, Ugo N. Di; Mapelli, Michela; Pasquato, Mario; Rastello, Sara; Ballone, Alessandro; Dall’Amico, Marco; Giacobbo, Nicola; Iorio, Giuliano; Spera, M.; Torniamenti, Stefano; Haardt, Francesco

doi:10.1093/mnras/stab2390

Cited by 57 publications

(33 citation statements)

References 154 publications

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“…As recently discovered in a number of numerical simulations of young massive clusters, IMBHs in the mass range 100 − 500 M can form either from the collision and merger of massive main sequence stars (e.g. Di Carlo et al 2021) or through the accretion of a massive star onto a stellar BH (e.g. Rizzuto et al 2021a).…”

Section: Implications Of Spectral Analysismentioning

confidence: 99%

Recurrent X-ray flares of the black hole candidate in the globular cluster RZ 2109 in NGC 4472

Tiengo

Esposito

Toscani

et al. 2022

A&A

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We report on the systematic analysis of the X-ray observations of the ultra-luminous X-ray source XMMU J122939.7+075333 located in the globular cluster RZ 2109 in the Virgo galaxy NGC 4472. The inclusion of observations and time intervals ignored in previous works and the careful selection of extraction regions and energy bands have allowed us to identify new flaring episodes, in addition to the ones that made it one of the best black hole candidates in globular clusters. Although most observations are too short and sparse to recognize a regular pattern, the spacing of the three most recent X-ray flares is compatible with a ≈34 hours recurrence time. If confirmed by future observations, such behavior, together with the soft spectrum of the X-ray flares, would be strikingly similar to the quasi-periodic eruptions recently discovered in galactic nuclei. Following one of the possible interpretations of these systems and of a peculiar class of extra-galactic X-ray transients, we explore the possibility that XMMU J122939.7+075333 might be powered by the partial disruption of a white dwarf by an intermediate mass (M ≈ 700 M ) black hole.

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Section: Implications Of Spectral Analysismentioning

confidence: 99%

Recurrent X-ray flares of the black hole candidate in the globular cluster RZ 2109 in NGC 4472

Tiengo

Esposito

Toscani

et al. 2022

A&A

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“…(i) dynamical BBH formation in dense stellar environments (e.g., Portegies Zwart & McMillan 2000;Askar et al 2017;Banerjee 2018;Di Carlo et al 2021). Repeated BH mergers (e.g., Rodriguez et al 2019;Antonini et al 2019;Samsing & Hotokezaka 2020;Fragione et al 2021;Arca Sedda et al 2021), BHs forming from dynamical stellar mergers or binary evolution mergers have been invoked to explain the formation of GW190521 in star clusters (e.g., Di Carlo et al 2020;Kremer et al 2020;Banerjee 2021;González et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…In low metallicity environments, where mass loss due to stellar winds is low, these massive stars may evolve into IMBH seeds (Spera & Mapelli 2017;Kremer et al 2020). It is also possible to form IMBH seeds in GCs through the gradual growth of stellar-mass BHs via mergers with other BHs or stars (Miller & Hamilton 2002;Giersz et al 2015;Rizzuto et al 2021;Di Carlo et al 2021). It has been shown that seed IMBHs of 10 2 −10 3 M can grow to larger masses through tidal capture and disruption of stars in extremely dense clusters (Alexander & Bar-Or 2017;Stone et al 2017;Sakurai et al 2019) with stellar densities 10 6 M pc −3 .…”

Section: Introductionmentioning

confidence: 99%

“…However, it may also be possible to eject out an IMBH in such interactions, particularly when a star cluster hosts multiple BHs with masses larger than 100 M . Although the possibility for an IMBH to escape from its host star cluster as a result of dynamical interactions has not been intensively studied, numerical studies indicate this can occur in realistic star clusters (Di Carlo et al 2021). Several works have investigated the ejection of IMBH and their seeds from star clusters due to gravitational wave recoil kicks following the merger of two BHs (e.g., Morawski et al 2018;Rodriguez et al 2019;Askar et al 2021b;Arca Sedda et al 2021;Rizzuto et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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MOCCA-SURVEY Database II -- Properties of Intermediate Mass Black Holes escaping from star clusters

Maliszewski,

Giersz,

Gondek-Rosińska

et al. 2021

Preprint

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In this work we investigate properties of intermediate-mass black holes (IMBHs) that escape from star clusters due to dynamical interactions. The studied models were simulated as part of the preliminary second survey carried out using the MOCCA code (MOCCA-SURVEY Database II), which is based on the Monte Carlo N-body method. We have found that IMBHs are more likely to be formed and ejected in models where both initial central density and central escape velocities have high values. Most of our studied objects escape in a binary with another black hole (BH) as their companion and they have masses between 100 and 140 M . Escaping IMBHs tend to build-up mass most effectively through repeated mergers in a binary with BHs due to gravitational wave emission. Binaries play a key role in their ejection from the system as they allow these massive objects to gather energy needed for escape. The binaries in which IMBHs escape tend to have very high binding energy at the time of escape and the last interaction is strong but does not involve a massive intruder. These IMBHs gain energy needed to escape the cluster gradually in successive dynamical interactions. We present specific examples of the history of IMBH formation and escape from our star cluster models. We also discuss the observational implications of our findings and estimate that the merger rate of ejected IMBH binaries from star clusters is R = 0.7 Gpc −3 yr −1 .

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“…A number of studies has shown that a likely venue to form an IMBH is the so-called runaway scenario, in the early phases of cluster evolution. In this process, the most massive stars segregate and merge in the core of the cluster, forming a massive growing object that could later collapse to form an IMBH (e.g., Portegies Zwart & McMillan 2002;Gürkan et al 2004;Freitag et al 2006;Giersz et al 2015;Kremer et al 2020;Di Carlo et al 2021;González et al 2021).…”

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confidence: 99%

Mergers of supermassive and intermediate-mass black holes in galactic nuclei from disruptions of star clusters

Fragione¹

2022

Preprint

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Gravitational waves (GWs) offer an unprecedented opportunity to survey the sky and detect mergers of compact objects. While intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt with either dynamical or accretion signatures, the GW landscape appears very promising. Mergers of an IMBH with a supermassive black hole (SMBH) will be primary sources for the planned space-based mission LISA and could be observed up to the distant Universe. SMBH-IMBH binaries can be formed as a result of the migration and merger of stellar clusters at the center of galaxies, where an SMBH lurks. We build for the first time a semi-analytical framework to model this scenario, and find that the the comoving merger rate of SMBH-IMBH binaries is ∼ 10 −3 Gpc −3 yr −1 in the local Universe for a unity IMBH occupation fraction, scales linearly with it, and has a peak at z ≈ 0.5-3. Our model predicts ∼ 1 event yr −1 within redshift z ≈ 3.5 if 10% of the inspiralled star clusters hosted an IMBH, while ∼ 10 events yr −1 for a unity occupation fraction. More than 90% of these systems will be detectable with LISA with a signal-to-noise ratio larger than 10, promising to potentially find a family of IMBHs.1. INTRODUCTION The formation and evolution of the innermost galactic regions is still uncertain. Most of the observed galactic nuclei harbour supermassive black holes (SMBHs), with masses ∼ 10 5 -10 9 (e.g., Ferrarese & Merritt 2000; Kormendy & Ho 2013). Galaxies across the entire Hubble sequence also show the presence of nucleated central regions, the nuclear star clusters (NSCs). NSCs are generally very massive, with mass up to a few times 10 7 M , and very dense, with half-light radius of a few pc (e.g., Georgiev et al. 2016;Neumayer et al. 2020). In some galaxies, as our own Milky Way, SMBHs and NSCs are found to co-exist (e.g., Capuzzo-Dolcetta & Tosta e Melo 2017).NSCs typically contain a predominant old stellar population, with age 1 Gyr, and show also the presence of a young stellar population, with age 100 Myr (e.g.,

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Intermediate-mass black holes from stellar mergers in young star clusters

Cited by 57 publications

References 154 publications

Recurrent X-ray flares of the black hole candidate in the globular cluster RZ 2109 in NGC 4472

Recurrent X-ray flares of the black hole candidate in the globular cluster RZ 2109 in NGC 4472

MOCCA-SURVEY Database II -- Properties of Intermediate Mass Black Holes escaping from star clusters

Mergers of supermassive and intermediate-mass black holes in galactic nuclei from disruptions of star clusters

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