Statistics for Stellar Systems: From Globular Clusters to Clusters of Galaxies

Both the radial and the velocity distributions of galaxies within rich clusters are well described by the isothermal distribution (e.g. Lewis 1978 and 1979). It is tempting to ascribe this apparently relaxed state to the operation of Lynden-BeU’s (1967) violent relaxation mechanism, during the initial coherent collapse on the proto-cluster, after it brakes itself against the universal expansion. This scenario explains the isothermal distribution observed in elliptical galaxies and globular clusters. When applied to a cluster of galaxies made up of baryons, however, the timescale for the scenario is comparable with the Hubble time H−1. The situation changes if most of the cluster mass is contributed by neutrinos.

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Photometric Models for Globular Clusters from Population Synthesis

Symposium - International Astronomical Union ◽

10.1017/s0074180900043060 ◽

1988 ◽

Vol 126 ◽

pp. 559-560

Author(s):

R. Capuzzo Dolcetta

Keyword(s):

Structural Properties ◽

Globular Clusters ◽

Magellanic Cloud ◽

Stellar Systems ◽

Population Synthesis ◽

Stellar Content ◽

Cloud Clusters ◽

Metal Abundance ◽

Theoretical Frame

Integral fluxes (Bolometric and U, B, V) are computed in a completely theoretical frame in order to investigate the structural properties and stellar content of coeval stellar systems of various ages and metal abundance. Some results concerning the problem of the color gap in the distribution of the sample of Magellanic Cloud clusters are discussed.

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Dynamical models of spheroidal multi-component stellar systems

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007294 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 273-276

Author(s):

Caterina Caravita ◽

Luca Ciotti ◽

Silvia Pellegrini

Keyword(s):

Globular Clusters ◽

Mass Function ◽

Mass Scale ◽

Initial Mass Function ◽

Dark Matter Halo ◽

Numerical Code ◽

Stellar Systems ◽

Rotating Disks ◽

Structural Density ◽

Systematic Effects

Abstract. We present a significantly improved version of our numerical code JASMINE, that can now solve the Jeans equations for axisymmetric models of stellar systems, composed of an arbitrary number of stellar populations, a Dark Matter halo, and a central Black Hole. The stellar components can have different structural (density profile, flattening, mass, scale length), dynamical (rotational support, velocity dispersion anisotropy), and population (age, metallicity, Initial Mass Function, mass-to-light ratio) properties. These models, when combined with observations, will allow to investigate important issues, such as quantifying the systematic effects of IMF variations, of mass-to-light ratio gradients, and of different stellar kinematic components (e.g. counter rotating disks, kinematically decoupled cores) on luminosity-weighted properties. The developed analytical and numerical framework aims at modeling Early-Type Galaxies, but it can also be applied to dwarf Spheroidal galaxies and Globular Clusters.

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petar: a high-performance N-body code for modelling massive collisional stellar systems

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1915 ◽

2020 ◽

Vol 497 (1) ◽

pp. 536-555 ◽

Cited By ~ 1

Author(s):

Long Wang ◽

Masaki Iwasawa ◽

Keigo Nitadori ◽

Junichiro Makino

Keyword(s):

Globular Clusters ◽

High Performance ◽

Computational Time ◽

Stellar Systems ◽

Processing Unit ◽

Desktop Computer ◽

Multiple Systems ◽

Hybrid Parallelization ◽

Good Agreement

ABSTRACT The numerical simulations of massive collisional stellar systems, such as globular clusters (GCs), are very time consuming. Until now, only a few realistic million-body simulations of GCs with a small fraction of binaries ($5{{\ \rm per\ cent}}$) have been performed by using the nbody6++gpu code. Such models took half a year computational time on a Graphic Processing Unit (GPU)-based supercomputer. In this work, we develop a new N-body code, petar, by combining the methods of Barnes–Hut tree, Hermite integrator and slow-down algorithmic regularization. The code can accurately handle an arbitrary fraction of multiple systems (e.g. binaries and triples) while keeping a high performance by using the hybrid parallelization methods with mpi, openmp, simd instructions and GPU. A few benchmarks indicate that petar and nbody6++gpu have a very good agreement on the long-term evolution of the global structure, binary orbits and escapers. On a highly configured GPU desktop computer, the performance of a million-body simulation with all stars in binaries by using petar is 11 times faster than that of nbody6++gpu. Moreover, on the Cray XC50 supercomputer, petar well scales when number of cores increase. The 10 million-body problem, which covers the region of ultracompact dwarfs and nuclear star clusters, becomes possible to be solved.

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Phase space complexity of star clusters: Fresh observables for old and new questions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007087 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 389-394

Author(s):

Anna Lisa Varri ◽

Philip G. Breen ◽

Douglas C. Heggie

Keyword(s):

Phase Space ◽

Globular Clusters ◽

Star Clusters ◽

Stellar Dynamics ◽

Stellar Systems ◽

Internal Dynamics ◽

The Rich ◽

Evolving Context ◽

New Generation ◽

Precision Astrometry

AbstractThe blooming era of precision astrometry for Galactic studies truly brings the rich internal dynamics of globular clusters to the centre stage. But several aspects of our current understanding of fundamental collisional stellar dynamics cannot match such new-generation data and the theoretical ambitions they trigger. This rapidly evolving context offers the stimulus to address a number of old and new questions concerning the phase space properties of this class of stellar systems.

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Rotation and Flattening of Globular Clusters

Symposium - International Astronomical Union ◽

10.1017/s007418090014745x ◽

1985 ◽

Vol 113 ◽

pp. 285-296 ◽

Cited By ~ 2

Author(s):

S. Michael Fall ◽

Carlos S. Frenk

Keyword(s):

Angular Momentum ◽

Internal Rotation ◽

Globular Clusters ◽

Pressure Support ◽

Initial Conditions ◽

Anisotropic Pressure ◽

Stellar Systems ◽

Galactic Globular Clusters

Pease and Shapley (1917) first remarked on the apparent flattening of several Galactic globular clusters, a view that has been confirmed by many subsequent studies. Tidal stresses, internal rotation, and velocity anisotropies can cause deviations from sphericity in stellar systems. In general, we might expect globular clusters to have some angular momentum at the time of formation and, if they collapsed from flattened initial conditions, to have anisotropic pressure support. Since the velocity distributions within the clusters can be altered by a variety of internal and external processes, their shapes are expected to evolve. In this article, we review the methods for measuring ellipticities and the results that have emerged from such studies. Our main purpose, however, is to discuss the processes that determine the shapes of globular clusters and the ways in which they change with time.

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On the Dynamical Evolution of Clusters of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900144821 ◽

1978 ◽

Vol 79 ◽

pp. 357-375 ◽

Cited By ~ 2

Author(s):

Jeremiah P. Ostriker

Keyword(s):

Globular Clusters ◽

Normal Modes ◽

Dynamical Evolution ◽

Second Law Of Thermodynamics ◽

Elliptical Galaxies ◽

Second Law ◽

Clusters Of Galaxies ◽

Physical Processes ◽

Rotating Systems ◽

Accurate Picture

The theory of the dynamics of star clusters (cf. Spitzer 1975 for a review) is by now so well developed that we have, or think we have, a moderately accurate picture of the physical processes acting in and the overall evolution of spherical systems. in contrast, flattened and/or rotating systems are apparently subject to a variety of ill-understood instabilities which ultimately are a manifestation of the second law of thermodynamics; at given total energy, a system will tend to increase the fraction of its kinetic energy in disordered rather than ordered form. But spherical systems (globular clusters, elliptical galaxies, Morgan cD clusters of galaxies) are relatively smooth and featureless; they show little substructure indicating, presumably, that they are quite stable to perturbations of their fundamental normal modes, and they are normally modeled as rather “hot”, pressure supported systems.

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A Morphological Classification of Clusters of Galaxies from Einstein Images

Symposium - International Astronomical Union ◽

10.1017/s0074180900027455 ◽

1982 ◽

Vol 97 ◽

pp. 97-106 ◽

Cited By ~ 2

Author(s):

C. Jones ◽

W. Forman

Keyword(s):

Line Emission ◽

Stellar Systems ◽

Single Individual ◽

Clusters Of Galaxies ◽

Morphological Classification ◽

Iron Line ◽

Emission Process ◽

X Ray ◽

Extended Sources

The earliest Uhuru observations showed that cluster X-ray sources were not associated with single individual galaxies but were extended sources (Gursky et al. 1971, Kellogg et al. 1972, and Forman et al. 1972). The detection of iron line emission from X-ray spectroscopic observations (Mitchell et al. 1976 and Serlemitsos et al. 1977) showed both that the dominant X-ray emission process was thermal bremsstrahlung and that the gas had been processed through stellar systems before being injected into the intracluster medium.

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Internal kinematics of multiple stellar populations in globular clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319006525 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 324-328

Author(s):

Mattia Libralato

Keyword(s):

High Precision ◽

Globular Clusters ◽

Hubble Space Telescope ◽

Stellar Populations ◽

Stellar Systems ◽

Proper Motions ◽

Space Telescope ◽

Formation And Evolution ◽

Galactic Globular Clusters ◽

Shed Light

AbstractSpectroscopy and photometry have revealed existence, complexity and properties of the multiple stellar populations (mPOPs) hosted in Galactic globular clusters. However, the conundrum of the formation and evolution of mPOPs is far from being completely exploited: the available pieces of information seem not enough to shed light on these topics. Astrometry, and in particular high-precision proper motions, can provide us the sought-after answers about how mPOPs formed and have evolved in these ancient stellar systems. In the following, I present a brief overview of the observational results on the internal kinematics of the mPOPs in some GCs thanks to Hubble Space Telescope high-precision proper motions.

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