Mass models of NGC 6624 without an intermediate-mass black hole

Gieles, M.; Balbinot, E.; Yaaqib, Rashid I. S. M.; Hénault-Brunet, V.; Zocchi, Alice; Peuten, M.; Jonker, P. G.

doi:10.1093/mnras/stx2694

Cited by 52 publications

(61 citation statements)

References 59 publications

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“…Our N-body simulations therefore confirm earlier results by Gieles et al (2018) who also found that no-IMBH is required to explain the observed surface brightness and velocity dispersion profile of NGC 6624. Models with IMBHs containing less than 5 per cent of the cluster mass in the form of an IMBH also provide acceptable fits to the velocity dispersion profile.…”

Section: Ngc 6624supporting

confidence: 90%

“…In addition, Perera et al (2017a, b) found evidence for a massive IMBH in NGC 6624 based on timing observations of several pulsars close to the cluster centre. However, Gieles et al (2018) were able to explain the observed period changes by a cluster model that did not contain an IMBH. In summary, there is currently no undisputed case for an IMBH in any Galactic globular cluster.…”

Section: Introductionmentioning

confidence: 90%

“…Furthermore, Perera et al (2017a) analysed timing observations of the three innermost pulsars in NGC 6624 and concluded that a 60 000 M IMBH (later revised down to 20 000 M by Perera et al 2017b) is required if their period changes are due to a central IMBH. Gieles et al (2018), on the other hand, noticed that the strong negative period derivative of 4U 1820-30 is not exceptional when compared to field LMXBs, making it likely that other explanations like mass-loss from the companion star or spin-orbit coupling can also explain the period change. They also showed through fitting of the observed surface brightness and velocity dispersion profile of NGC 6624 by multimass models that models without an IMBH are sufficient to explain the observed acceleration of pulsar A in NGC 6624.…”

Section: Implication For the Initial Stellar-mass Black Hole Retentiomentioning

confidence: 99%

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No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

Baumgardt

Sweet

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We compare the results of a large grid of N-body simulations with the surface brightness and velocity dispersion profiles of the globular clusters ω Cen and NGC 6624. Our models include clusters with varying stellar-mass black hole retention fractions and varying masses of a central intermediate-mass black hole (IMBH). We find that an ∼ 45 000 M IMBH, whose presence has been suggested based on the measured velocity dispersion profile of ω Cen, predicts the existence of about 20 fast-moving, m > 0.5 M , main-sequence stars with a (1D) velocity v > 60 km s −1 in the central 20 arcsec of ω Cen. However, no such star is present in the HST/ACS proper motion catalogue of Bellini et al. (2017), strongly ruling out the presence of a massive IMBH in the core of ω Cen. Instead, we find that all available data can be fitted by a model that contains 4.6 per cent of the mass of ω Cen in a centrally concentrated cluster of stellar-mass black holes. We show that this mass fraction in stellar-mass BHs is compatible with the predictions of stellar evolution models of massive stars. We also compare our grid of N-body simulations with NGC 6624, a cluster recently claimed to harbour a 20 000 M black hole based on timing observations of millisecond pulsars. However, we find that models with M IMBH > 1000 M IMBHs are incompatible with the observed velocity dispersion and surface brightness profile of NGC 6624, ruling out the presence of a massive IMBH in this cluster. Models without an IMBH provide again an excellent fit to NGC 6624.

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Section: Ngc 6624supporting

confidence: 90%

Section: Introductionmentioning

confidence: 90%

Section: Implication For the Initial Stellar-mass Black Hole Retentiomentioning

confidence: 99%

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No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

Baumgardt

Sweet

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Other scenarios, invoking runaway collisions of massive stars and/or the collapse of a very massive star ( 200M ⊙ ) could also lead to the formation of IMBHs in globular clusters (e.g., Portegies Zwart & McMillan (2002), Gürkan et al (2004), Portegies Zwart et al (2004a), Portegies Zwart et al (2004b), Freitag et al (2006), Mapelli (2016), Gieles et al (2018b), and Section 3.2). A GW detection may be the most promising route to search for IMBHs in globular clusters, because a convincing detection with other methods remains elusive (Anderson & van der Marel 2010;Lanzoni et al 2013;Gieles et al 2018a;Tremou et al 2018; Amaro-Seoane 2018b).…”

Section: Globular Clustersmentioning

confidence: 99%

Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections

Antonini

Gieles

Gualandris

2019

Monthly Notices of the Royal Astronomical Society

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225

196

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In a star cluster with a sufficiently large escape velocity, black holes (BHs) that are produced by BH mergers can be retained, dynamically form new BH binaries, and merge again. This process can repeat several times and lead to significant mass growth. In this paper, we calculate the mass of the largest BH that can form through repeated BH mergers and determine how its value depends on the physical properties of the host cluster. We adopt an analytical model in which the energy generated by the black hole binaries in the cluster core is assumed to be regulated by the process of two-body relaxation in the bulk of the system. This principle is used to compute the hardening rate of the binaries and to relate this to the time-dependent global properties of the parent cluster. We demonstrate that in clusters with initial escape velocity 300 km s −1 in the core and density 10 5 M ⊙ pc −3 , repeated mergers lead to the formation of BHs in the mass range 100 − 10 5 M ⊙ , populating any upper mass gap created by pair-instability supernovae. This result is independent of cluster metallicity and the initial BH spin distribution. We show that about 10% of the present-day nuclear star clusters meet these extreme conditions, and estimate that BH binary mergers with total mass 100 M ⊙ should be produced in these systems at a maximum rate ≈ 0.05 Gpc −3 yr −1 , corresponding to one detectable event every few years with Advanced LIGO/Virgo at design sensitivity.

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“…There has been an abundance of claims, usually followed by counter-claims, for the existence of IMBHs in large globular clusters. For example, see the studies of: G1, the most massive globular cluster around M31 (Gebhardt et al 2005;Miller-Jones et al 2012); ω Centauri, the most massive globular cluster around the Milky Way (Noyola et al 2008;Haggard et al 2013;Zocchi et al 2017Zocchi et al , 2019; plus other globular clusters around the Milky Way such as M15 (Gebhardt et al 2000;Gerssen et al 2002;Baumgardt et al 2003;Kirsten & Vlemmings 2012;den Brok et al 2014;Kirsten et al 2014); M54 (Ibata et al 2009); 47 Tucanae (Kızıltan et al 2017;Abbate et al 2018;Mann et al 2019);and NGC 6624 (Perera et al 2017;Gieles et al 2018;Baumgardt et al 2019). To date, there remains no conclusive evidence for IMBHs in globular clusters (Hurley 2007;Vesperini & Trenti 2010;Lanzoni & Cosmic-Lab Team 2016;Maccarone 2016;Wrobel et al 2016;Ferraro et al 2018;Tremou et al 2018), although see ).…”

Section: Introductionmentioning

confidence: 99%

A consistency test for determining whether ultracompact dwarf galaxies could be the remnant nuclei of threshed galaxies

Graham

2019

Monthly Notices of the Royal Astronomical Society

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It has been suggested that ultra-compact dwarf (UCD) galaxies are the "threshed" remains of larger galaxies. Simulations have revealed that extensive tidal-stripping may pare a galaxy back to its tightly-bound, compact nuclear star cluster. It has therefore been proposed that the two-component nature of UCD galaxies may reflect the original nuclear star cluster surrounded by the paltry remnants of its host galaxy. A simple quantitative test of this theory is devised and applied here. If the mass of the central black hole in UCD galaxies, relative to the mass of the UCD galaxies' inner stellar component, i.e. the suspected nuclear star cluster, matches with the (black hole mass)-(nuclear star cluster mass) relation observed in other galaxies, then it would provide quantitative support for the stripped galaxy scenario. Such consistency is found for four of the five UCD galaxies reported to have a massive black hole. This (black hole mass)-(nuclear star cluster mass) relation is then used to predict the central black hole mass in two additional UCD galaxies, and to reveal that NGC 205 and possibly NGC 404 (which only has an upper limit to its black hole mass) also follow this scaling relation.1 While grossly over-represented in some published scaling diagrams, at a given luminosity, just 0.5 percent of dwarf galaxies are "compact elliptical" galaxies (Chilingarian, private communication).

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Mass models of NGC 6624 without an intermediate-mass black hole

Cited by 52 publications

References 59 publications

No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624

Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections

A consistency test for determining whether ultracompact dwarf galaxies could be the remnant nuclei of threshed galaxies

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