Mass Segregation as a New Indicator of Binary, IMBH, and Stellar-mass Black Hole Systems in Globular Clusters

ABSTRACT 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 $\sim 45\, 000$ 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 MIMBH > 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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mocca-survey Database I: Binary black hole mergers from globular clusters with intermediate mass black holes

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2677 ◽

2020 ◽

Vol 498 (3) ◽

pp. 4287-4294

Author(s):

Jongsuk Hong ◽

Abbas Askar ◽

Mirek Giersz ◽

Arkadiusz Hypki ◽

Suk-Jin Yoon

Keyword(s):

Black Holes ◽

Black Hole ◽

Gravitational Waves ◽

Globular Clusters ◽

Stellar Mass ◽

Intermediate Mass ◽

Binary Black Holes ◽

Black Hole Binaries ◽

Binary Black Hole ◽

Intermediate Mass Black Holes

ABSTRACT The dynamical formation of black hole binaries in globular clusters that merge due to gravitational waves occurs more frequently in higher stellar density. Meanwhile, the probability to form intermediate mass black holes (IMBHs) also increases with the density. To explore the impact of the formation and growth of IMBHs on the population of stellar mass black hole binaries from globular clusters, we analyse the existing large survey of Monte Carlo globular cluster simulation data (mocca-survey Database I). We show that the number of binary black hole mergers agrees with the prediction based on clusters’ initial properties when the IMBH mass is not massive enough or the IMBH seed forms at a later time. However, binary black hole formation and subsequent merger events are significantly reduced compared to the prediction when the present-day IMBH mass is more massive than ${\sim}10^4\, \rm M_{\odot }$ or the present-day IMBH mass exceeds about 1 per cent of cluster’s initial total mass. By examining the maximum black hole mass in the system at the moment of black hole binary escaping, we find that ∼90 per cent of the merging binary black holes escape before the formation and growth of the IMBH. Furthermore, large fraction of stellar mass black holes are merged into the IMBH or escape as single black holes from globular clusters in cases of massive IMBHs, which can lead to the significant underpopulation of binary black holes merging with gravitational waves by a factor of 2 depending on the clusters’ initial distributions.

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Exploring the Mass Segregation Effect of X-Ray Sources in Globular Clusters. IV. Evidence of Black Hole Burning in ω Centauri

The Astrophysical Journal ◽

10.3847/1538-4357/abbdfc ◽

2020 ◽

Vol 904 (2) ◽

pp. 198

Author(s):

Zhongqun Cheng ◽

Zhiyuan Li ◽

Wei Wang ◽

Xiangdong Li ◽

Xiaojie Xu

Keyword(s):

Black Hole ◽

Globular Clusters ◽

Hole Burning ◽

X Ray ◽

Segregation Effect ◽

Mass Segregation

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Effects of Stellar-Mass Black Holes on Massive Star Cluster Evolution

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315010674 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 234-239

Author(s):

Sourav Chatterjee ◽

Meagan Morscher ◽

Carl L. Rodriguez ◽

Bharat Pattabiraman ◽

Frederic A. Rasio

Keyword(s):

Globular Clusters ◽

Massive Star ◽

Star Clusters ◽

Mass Function ◽

Stellar Mass ◽

Cluster Center ◽

Cluster Evolution ◽

Large Populations ◽

Direct Contrast ◽

Mass Segregation

AbstractRecent observations have revealed the existence of stellar mass black hole (BH) candidates in some globular clusters (GC) in the Milky Way and in other galaxies. Given that the detection of BHs is challenging, these detections likely indicate the existence of large populations of BHs in these clusters. This is in direct contrast to the past understanding that at most a handful of BHs may remain in old GCs due to quick mass segregation and rapid mutual dynamical ejection. Modern realistic star-by-star numerical simulations suggest that the retention fraction of BHs is typically much higher than what was previously thought. The BH dynamics near the cluster center leads to dynamical formation of new binaries and dynamical ejections, and acts as a persistent and significant energy source for these clusters. We have started exploring effects of BHs on the global evolution and survival of star clusters. We find that the evolution as well as survival of massive star clusters can critically depend on the details of the initial assumptions related to BH formation physics, such as natal kick distribution, and the initial stellar mass function (IMF). In this article we will present our latest results.

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Space Telescope Observations of Globular Clusters

Symposium - International Astronomical Union ◽

10.1017/s0074180900147722 ◽

1985 ◽

Vol 113 ◽

pp. 481-498

Author(s):

John N. Bahcall

Keyword(s):

Black Hole ◽

Globular Clusters ◽

Luminosity Function ◽

Elliptical Galaxies ◽

Core Collapse ◽

Massive Black Hole ◽

Space Telescope ◽

Galactic Clusters ◽

Mass Segregation

Six proposed Space Telescope programs involving globular clusters are described. The projects appropriate for galactic clusters are: the detection of white dwarfs, the study of the faint end of the Population II luminosity function, the measurement of mass segregation, and the search for a cusp in the density distribution caused by core collapse or by a massive black hole. The two programs that involve extragalactic globular clusters are: the determination of the luminosity function of clusters around different galaxies and the measurement of tidal radii of clusters surrounding elliptical galaxies.

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A stellar census in globular clusters with MUSE: Binaries in NGC 3201

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936203 ◽

2019 ◽

Vol 632 ◽

pp. A3 ◽

Cited By ~ 25

Author(s):

Benjamin Giesers ◽

Sebastian Kamann ◽

Stefan Dreizler ◽

Tim-Oliver Husser ◽

Abbas Askar ◽

...

Keyword(s):

Black Hole ◽

Binary System ◽

Radial Velocity ◽

Binary Stars ◽

Globular Clusters ◽

Spectroscopic Properties ◽

Spectroscopic Studies ◽

The Core ◽

Blue Straggler ◽

Mass Segregation

We utilise multi-epoch MUSE spectroscopy to study binary stars in the core of the Galactic globular cluster NGC 3201. Our sample consists of 3553 stars with 54 883 spectra in total comprising 3200 main-sequence stars up to 4 magnitudes below the turn-off. Each star in our sample has between 3 and 63 (with a median of 14) reliable radial velocity measurements within five years of observations. We introduce a statistical method to determine the probability of a star showing radial velocity variations based on the whole inhomogeneous radial velocity sample. Using HST photometry and an advanced dynamical MOCCA simulation of this specific cluster we overcome observational biases that previous spectroscopic studies had to deal with. This allows us to infer a binary frequency in the MUSE field of view and enables us to deduce the underlying true binary frequency of (6.75 ± 0.72)% in NGC 3201. The comparison of the MUSE observations with the MOCCA simulation suggests a large portion of primordial binaries. We can also confirm a radial increase in the binary fraction towards the cluster centre due to mass segregation. We discovered that in the core of NGC 3201 at least (57.5 ± 7.9)% of blue straggler stars are in a binary system. For the first time in a study of globular clusters, we were able to fit Keplerian orbits to a significant sample of 95 binaries. We present the binary system properties of eleven blue straggler stars and the connection to SX Phoenicis-type stars. We show evidence that two blue straggler formation scenarios, the mass transfer in binary (or triple) star systems and the coalescence due to binary-binary interactions, are present in our data. We also describe the binary and spectroscopic properties of four sub-subgiant (or red straggler) stars. Furthermore, we discovered two new black hole candidates with minimum masses (M sin i) of (7.68 ± 0.50) M⊙, (4.4 ± 2.8) M⊙, and refine the minimum mass estimate on the already published black hole to (4.53 ± 0.21) M⊙. These black holes are consistent with an extensive black hole subsystem hosted by NGC 3201.

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Predicting Stellar-mass Black Hole Populations in Globular Clusters

The Astrophysical Journal ◽

10.3847/1538-4357/aad63d ◽

2018 ◽

Vol 864 (1) ◽

pp. 13 ◽

Cited By ~ 18

Author(s):

Newlin C. Weatherford ◽

Sourav Chatterjee ◽

Carl L. Rodriguez ◽

Frederic A. Rasio

Keyword(s):

Black Hole ◽

Globular Clusters ◽

Stellar Mass

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Globular Clusters within Dark Matter Halos: Case Studies of 47 Tuc, NGC 1851 and M 15

Proceedings of the International Astronomical Union ◽

10.1017/s174392131500890x ◽

2015 ◽

Vol 12 (S316) ◽

pp. 336-337

Author(s):

Joowon Lee ◽

Jihye Shin ◽

Sungsoo S. Kim

Keyword(s):

Dark Matter ◽

Case Studies ◽

Globular Clusters ◽

Dynamical Evolution ◽

Stellar Mass ◽

Dark Matter Halos ◽

Dynamical Processes ◽

Mass Segregation ◽

Fokker Planck

AbstractGlobular clusters (GCs) are known to have a very small amount of or no dark matter (DM). Even if GCs are formed in individual DM halos, they must have lost the majority of the DM through dynamical processes such as mass segregation or tidal stripping. Using Fokker-Planck (FP) calculations, we investigate the dynamical evolution of three Galactic GCs with an assumption that they were formed in mini DM halos. We trace the amount of DM of 47 Tuc, NGC 1851, and M 15, which are a ‘disk/bulge’ cluster, an ‘old halo’ cluster, and a ‘young halo’ cluster, respectively. We find that these three GCs must have initially had insignificant amounts of DM, less than 10 percent of the initial stellar mass of each cluster.

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Substructure in black hole scaling diagrams and implications for the coevolution of black holes and galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001726 ◽

2019 ◽

Vol 15 (S359) ◽

pp. 37-39

Author(s):

Benjamin L. Davis ◽

Nandini Sahu ◽

Alister W. Graham

Keyword(s):

Black Hole ◽

Stellar Mass ◽

Host Galaxy ◽

Scaling Relations ◽

Black Hole Mass ◽

Physical Processes ◽

Stellar Velocity ◽

Galaxy Sample ◽

Evolutionary Paths ◽

Black Hole Masses

AbstractOur multi-component photometric decomposition of the largest galaxy sample to date with dynamically-measured black hole masses nearly doubles the number of such galaxies. We have discovered substantially modified scaling relations between the black hole mass and the host galaxy properties, including the spheroid (bulge) stellar mass, the total galaxy stellar mass, and the central stellar velocity dispersion. These refinements partly arose because we were able to explore the scaling relations for various sub-populations of galaxies built by different physical processes, as traced by the presence of a disk, early-type versus late-type galaxies, or a Sérsic versus core-Sérsic spheroid light profile. The new relations appear fundamentally linked with the evolutionary paths followed by galaxies, and they have ramifications for simulations and formation theories involving both quenching and accretion.

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