The onset of gravothermal oscillations in globular cluster evolution

Breeden, Joseph L.; Cohn, H. N.; Hut, Piet

doi:10.1086/173636

Cited by 23 publications

(27 citation statements)

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“…It should be noted that for oscillations observed in MonteCarlo simulations there is no clear transition from regular oscillations to chaotic ones or from stable expansion to oscillations. Features observed in gas and Fokker-Planck models (Heggie & Ramamani 1989, Breeden et al 1994. However, the present results are consistent with results obtained by Takahashi & Inagaki (1991) for stochastic Fokker-Planck model (stochastic binary formation and energy generation), by Makino (1996ab) for N -body simulations and by Giersz & Spurzem (1997) for anisotropic gaseous model with fully self-consistent Monte-Carlo treatment of binary population.…”

Section: First Resultssupporting

confidence: 92%

“…The number of particles at the phases of maximum contraction is around 20, while for the phases of maximum expansion is around 1000. This result is in excellent agreement with N -body calculations (Makino 1996ab) and as well with gas and Fokker-Planck calculations (Heggie & Ramamani 1989, Breeden et al 1994. This further strengthen the fact that gravothermal oscillations observed in the Monte-Carlo simulations are practically undistinguished from that for direct N -body simulations.…”

Section: First Resultssupporting

confidence: 87%

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Monte Carlo simulations of star clusters - I. First Results

Giersz

1998

Monthly Notices RAS

149

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A revision of Stodó lkiewicz's Monte-Carlo code is used to simulate evolution of star clusters. The new method treats each superstar as a single star and follows the evolution and motion of all individual stellar objects. The first calculations for isolated, equal-mass N -body systems with three-body energy generation according to Spitzer's formulae show good agreement with direct N -body calculations for N = 2000, 4096 and 10000 particles. The density, velocity, mass distributions, energy generation, number of binaries etc. follow the N -body results. Only the number of escapers is slightly too high compared to N -body results and there is no level off anisotropy for advanced post-collapse evolution of Monte-Carlo models as is seen in N -body simulations for N ≤ 2000. For simulations with N > 10000 gravothermal oscillations are clearly visible. The calculations of N = 2000, 4096, 10000, 32000 and 100000 models take about 2, 6 20, 130 and 2500 hours, respectively. The Monte-Carlo code is at least 10 5 times faster than the N -body one for N = 32768 with special-purpose hardware (Makino 1996ab). Thus it becomes possible to run several different models to improve statistical quality of the data and run individual models with N as large as 100000. The MonteCarlo scheme can be regarded as a method which lies in the middle between direct N -body and Fokker-Planck models and combines most advantages of both methods.

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Section: First Resultssupporting

confidence: 92%

Section: First Resultssupporting

confidence: 87%

Monte Carlo simulations of star clusters - I. First Results

Giersz

1998

Monthly Notices RAS

149

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“…The relaxation time for ω Cen implies a much slower dynamical evolution than the one necessary to reach such a configuration. Core-collapse models have shown that when a cluster has reached such a high degree of mass segregation, the observable core to half light radius gets very small, with values below 0.05 (Breeden, Cohn, & Hut 1994), while this ratio is 0.3 for ω Cen. Another possibility is that the observed rise in velocity dispersion is due to velocity anisotropy in the cluster.…”

Section: Modelsmentioning

confidence: 99%

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

2007

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Abstract. The 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. 75We 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.

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“…Although this phenomenon is based on purely thermodynamic considerations, it is referred to as gravothermal catastrophe [9]. For energy less than the critical value, collapse is possible and suggested by both theory and simulation [5,10,11]. Core-collapsed clusters have been recognized as possible candidates for stellar clusters undergoing gravothermal collapse.…”

mentioning

confidence: 99%

“…In stellar systems, it was first recognized by Henon that an internal energy source supplied by binaries (binary heating) can cause the reexpansion of a globular cluster core [22]. Later, these oscillations were confirmed in Fokker-Planck simulations [10] by considering binary-single star and binary-binary encounters as the internal heat source in the core. The stability of the reexpansion depends on the total number of particles and strength of the heating mechanism, and oscillations can develop in the central density.…”

mentioning

confidence: 99%

Dynamical Simulation of Gravothermal Catastrophe

Klinko

Miller

2004

Phys. Rev. Lett.

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We investigate the dynamical evolution of gravothermal catastrophe in a model of a spherical cluster where, besides the energy and angular momentum, an additional integral of motion is also taken into account. Using dynamical simulation, we study a system of concentric, rotating, spherical shells employing a precise, event-driven, algorithm that permits the controlled exchange of internal angular momentum. Initially the system starts to relax to a locally stable state that is in good agreement with mean field predictions. This is followed by core collapse with the development of a core-halo structure and gravothermal oscillation.

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The onset of gravothermal oscillations in globular cluster evolution

Cited by 23 publications

References 0 publications

Monte Carlo simulations of star clusters - I. First Results

Monte Carlo simulations of star clusters - I. First Results

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

Dynamical Simulation of Gravothermal Catastrophe

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