scholarly journals Black-Hole Remnants in Globular Clusters

1985 ◽  
Vol 113 ◽  
pp. 421-422
Author(s):  
Richard B. Larson
Keyword(s):  
Black Hole ◽  
Density Profile ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Relaxation Times ◽  
Stellar System ◽  
Core Collapse ◽  
The Core ◽  
Singular Form ◽  
Light Profiles

Many presentations at this meeting have discussed the phenomenon of “core collapse”, and it seems agreed that a stellar system like a globular cluster will, within a few half-mass relaxation times, undergo a runaway increase in central density and achieve a nearly singular density distribution with a logarithmic gradient slightly steeper than −2. The collapse is halted by the formation of binaries when the core has shrunk to contain only a small number of stars, and the system subsequently expands gradually while maintaining a density profile approximating that of a singular isothermal sphere. Light profiles resembling the predicted nearly singular form have been found in a small number of globular clusters (Djorgovski, this meeting), but a puzzle remains in that many more clusters should have undergone core collapse, yet they show quite flat light profiles in their cores.

scholarly journals Dynamical Evolution of Globular Clusters After Core Collapse

1985 ◽  
Vol 113 ◽  
pp. 139-160 ◽  
Author(s):  
Douglas C. Heggie
Keyword(s):  
Surface Density ◽  
Globular Clusters ◽  
Stellar System ◽  
Dynamical Evolution ◽  
Theoretical Models ◽  
Numerical Calculations ◽  
Core Collapse ◽  
Density Profiles ◽  
The Core ◽  
Fokker Planck

This review describes work on the evolution of a stellar system during the phase which starts at the end of core collapse. It begins with an account of the models of Hénon, Goodman, and Inagaki and Lynden-Bell, as well as evaporative models, and modifications to these models which are needed in the core. Next, these models are related to more detailed numerical calculations of gaseous models, Fokker-Planck models, N-body calculations, etc., and some problems for further work in these directions are outlined. The review concludes with a discussion of the relation between theoretical models and observations of the surface density profiles and statistics of actual globular clusters.

scholarly journals Central Dynamics of Globular Clusters: the Case for a Black Hole in ω Centauri

2007 ◽  
Vol 3 (S246) ◽  
pp. 341-345
Author(s):  
Eva Noyola ◽  
Karl Gebhardt ◽  
Marcel Bergmann
Keyword(s):  
Black Hole ◽  
Relaxation Time ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Dwarf Galaxy ◽  
Kinematic Data ◽  
The Core ◽  
Galactic System ◽  
Interesting Candidate ◽  
Radial Anisotropy

AbstractThe globular cluster ω Centauri is one of the largest and most massive members of the Galactic system. Its classification as a globular cluster has been challenged making it a candidate for being the stripped core of an accreted dwarf galaxy; this and the fact that it has one of the largest velocity dispersions for star clusters in our galaxy makes it an interesting candidate for harboring an intermediate mass black hole. We measure the surface brightness profile from integrated light on an HST/ACS image, and find a central power-law cusp of logarithmic slope -0.08. We also analyze Gemini GMOS-IFU kinematic data for a 5”x5” field centered on the nucleus of the cluster, as well as for a field 14″ away. We detect a clear rise in the velocity dispersion from 18.6 kms−1 at 14″ to 23 kms−1 in the center. Given the very large core in ω Cen (2.58'), an increase in the dispersion in the central 10″ is difficult to attribute to stellar remnants, since it requires too many dark remnants and the implied configuration would dissolve quickly given the relaxation time in the core. However, the increase could be consistent with the existence of a central black hole. Assuming a constant M/L for the stars within the core, the dispersion profile from these data and data at larger radii implies a black hole mass of 4.0+0.75−1.0×104M⊙. We have also run flattened, orbit-based models and find a similar mass. In addition, the no black hole case for the orbit model requires an extreme amount of radial anisotropy, which is difficult to preserve given the short relaxation time of the cluster.

scholarly journals Can a Moderately Massive Black Hole Reverse Core Collapse?

1985 ◽  
Vol 113 ◽  
pp. 415-417
Author(s):  
Martin J. Duncan
Keyword(s):  
Heat Flux ◽  
Black Hole ◽  
Binding Energy ◽  
Globular Cluster ◽  
Total Mass ◽  
Relaxation Times ◽  
Core Collapse ◽  
Massive Black Hole ◽  
Core Mass ◽  
M 10

Direct N-body simulations show that the heat flux from the cusp of stars surrounding an object of mass M ~ 10–100 M⊙ has a profound effect on the evolution of a cluster of N stars of mass m ~ 1 M⊙. A cluster containing an object which is ≳ 5% of its total mass expands, transferring most of the cluster binding energy to a few stars deep in the cusp within several central relaxation times. The results, together with analytic estimates, suggest that core collapse in a globular cluster will be reversed when the core mass is reduced to ~10 M. As is discussed below, this result does not depend on whether or not stars are disrupted by the black hole.

scholarly journals The Role of “black hole burning” in the evolution of dense star clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 357-366
Author(s):  
Kyle Kremer ◽  
Claire S. Ye ◽  
Sourav Chatterjee ◽  
Carl L. Rodriguez ◽  
Frederic A. Rasio
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
Star Clusters ◽  
Bimodal Distribution ◽  
Hole Burning ◽  
Core Collapse ◽  
Dynamical Interaction ◽  
The Core ◽  
Natural Tendency ◽  
Gravitating Systems

AbstractAs self-gravitating systems, dense star clusters exhibit a natural diffusion of energy from their innermost to outermost regions, leading to a slow and steady contraction of the core until it ultimately collapses under gravity. However, in spite of the natural tendency toward “core collapse,” the globular clusters (GCs) in the Milky Way exhibit a well-observed bimodal distribution in core radii separating the core-collapsed and non-core-collapsed clusters. This suggests an internal energy source is at work, delaying the onset of core collapse in many clusters. Over the past decade, a large amount of work has suggested that stellar black holes (BHs) play a dynamically-significant role in clusters throughout their entire lifetimes. Here we review our latest understanding of BH populations in GCs and demonstrate that, through their dynamical interaction with their host cluster, BHs can naturally explain the distinction between core-collapsed and non-core-collapsed clusters through a process we call “black hole burning.”

scholarly journals Slow decline and rise of the broad [O iii] emission line in globular cluster black hole candidate RZ2109

2019 ◽  
Vol 489 (4) ◽  
pp. 4783-4790 ◽  
Author(s):  
Kristen C Dage ◽  
Stephen E Zepf ◽  
Arash Bahramian ◽  
Jay Strader ◽  
Thomas J Maccarone ◽  
...  
Keyword(s):  
Black Hole ◽  
Emission Line ◽  
Globular Clusters ◽  
X Ray ◽  
Hydrogen Emission ◽  
Black Hole Candidate ◽  
The Core ◽  
Spectroscopic Monitoring ◽  
Slow Decline ◽  
Over Time

ABSTRACT RZ2109 is the first of several extragalactic globular clusters shown to host an ultraluminous X-ray source. RZ2109 is particularly notable because optical spectroscopy shows it has broad, luminous [O iii] λλ4959,5007 emission, while also having no detectable hydrogen emission. The X-ray and optical characteristics of the source in RZ2109 make it a good candidate for being a stellar mass black hole accreting from a white dwarf donor (i.e. an ultracompact black hole X-ray binary). In this paper we present optical spectroscopic monitoring of the [O iii]5007 emission line from 2007 to 2018. We find that the flux of the emission line is significantly lower in recent observations from 2016 to 2018 than it was in earlier observations in 2007–2011. We also explore the behaviour of the emission line shape over time. Both the core and the wings of the emission line decline over time, with some evidence that the core declines more rapidly than the wings. However, the most recent observations (in 2019) unexpectedly show the emission line core rebrightening

scholarly journals Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 19-28
Author(s):  
Puragra Guhathakurta ◽  
Brian Yanny ◽  
Donald P. Schneider ◽  
John N. Bahcall
Keyword(s):  
Density Profile ◽  
Globular Clusters ◽  
Hubble Space Telescope ◽  
Stellar Populations ◽  
Core Collapse ◽  
Red Giants ◽  
Space Telescope ◽  
Blue Straggler ◽  
Central Regions ◽  
Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

scholarly journals On the survivability of planets in young massive clusters and its implication of planet orbital architectures in globular clusters

2019 ◽  
Vol 489 (3) ◽  
pp. 4311-4321 ◽  
Author(s):  
Maxwell X Cai ◽  
S Portegies Zwart ◽  
M B N Kouwenhoven ◽  
Rainer Spurzem
Keyword(s):  
Globular Cluster ◽  
Time Scale ◽  
Globular Clusters ◽  
Semimajor Axis ◽  
Stellar System ◽  
Dynamical Evolution ◽  
The Other ◽  
Crossing Time ◽  
Massive Clusters ◽  
Full Investigation

ABSTRACT As of 2019 August, among the more than 4000 confirmed exoplanets, only one has been detected in a globular cluster (GC) M4. The scarce of exoplanet detections motivates us to employ direct N-body simulations to investigate the dynamical stability of planets in young massive clusters (YMC), which are potentially the progenitors of GCs. In an N = 128 k cluster of virial radius 1.7 pc (comparable to Westerlund-1), our simulations show that most wide-orbit planets (a ≥ 20 au) will be ejected within a time-scale of 10 Myr. Interestingly, more than $70{{\ \rm per\ cent}}$ of planets with a < 5 au survive in the 100 Myr simulations. Ignoring planet–planet scattering and tidal damping, the survivability at t Myr as a function of initial semimajor axis a0 in au in such a YMC can be described as fsurv(a0, t) = −0.33log10(a0)(1 − e−0.0482t) + 1. Upon ejection, about $28.8{{\ \rm per\ cent}}$ of free-floating planets (FFPs) have sufficient speeds to escape from the host cluster at a crossing time-scale. The other FFPs will remain bound to the cluster potential, but the subsequent dynamical evolution of the stellar system can result in the delayed ejection of FFPs from the host cluster. Although a full investigation of planet population in GCs requires extending the simulations to multiGyr, our results suggest that wide-orbit planets and free-floating planets are unlikely to be found in GCs.

scholarly journals Erratum: Binary black hole mergers from globular clusters: the impact of globular cluster properties

2019 ◽  
Vol 491 (4) ◽  
pp. 5793-5793
Author(s):  
Jongsuk Hong ◽  
Enrico Vesperini ◽  
Abbas Askar ◽  
Mirek Giersz ◽  
Magdalena Szkudlarek ◽  
...  
Keyword(s):  
Black Hole ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Binary Black Hole ◽  
Cluster Properties ◽  
The Impact

scholarly journals Truncation of the Binary Distribution Function in Globular Cluster Formation

1996 ◽  
Vol 174 ◽  
pp. 403-404
Author(s):  
E. Vesperini ◽  
D.F. Chernoff
Keyword(s):  
Distribution Function ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Core Collapse ◽  
Direct Impact ◽  
Expansion Phase ◽  
Binary Distribution ◽  
The Core ◽  
Binary Distribution Function ◽  
Cluster A

Recent observational searches suggest that the frequency of primordial binaries in globular clusters may reach ~ 10% (see Hut et al. 1992 for a review). Several different treatments conclude that primordial binaries are effective in halting core collapse, supporting the core and driving the post-core collapse expansion phase (Goodman & Hut 1989, McMillan et al. 1990, 1991, Gao et al. 1991, Heggie & Aarseth 1992, McMillan & Hut 1994). The abundance and binding energy distribution have a direct impact on observable characteristics of globular clusters such as the size of the core radius (Vesperini & Chernoff 1994). In this analysis we have investigated how the initial binary distribution function may be altered in the formation of a cluster; the key question we have addressed is whether it is possible for binaries, assumed to be primordial, to survive the birth of the cluster. A detailed description of our results is in Vesperini & Chernoff (1995).

scholarly journals The Core of the M 87 Globular Cluster System

1988 ◽  
Vol 126 ◽  
pp. 607-608
Author(s):  
Tod R. Lauer ◽  
John Kormendy
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Cluster System ◽  
Core Radius ◽  
The Core ◽  
Order Of Magnitude ◽  
Globular Cluster System

We have observed the central distribution of globular clusters in M 87. The core radius of the cluster system is an order of magnitude larger than that of the underlying galaxy.

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