scholarly journals Star cluster dynamics

2010 ◽  
Vol 368 (1913) ◽  
pp. 829-849 ◽  
Author(s):  
Enrico Vesperini
Keyword(s):  
Globular Clusters ◽  
Cluster Formation ◽  
Cluster Structure ◽  
Dynamical Evolution ◽  
Star Cluster ◽  
Stellar Content ◽  
Cluster Systems ◽  
Detailed Understanding ◽  
Term Evolution

Dynamical evolution plays a key role in shaping the current properties of star clusters and star cluster systems. A detailed understanding of the effects of evolutionary processes is essential to be able to disentangle the properties that result from dynamical evolution from those imprinted at the time of cluster formation. In this review, I focus my attention on globular clusters, and review the main physical ingredients driving their early and long-term evolution, describe the possible evolutionary routes and show how cluster structure and stellar content are affected by dynamical evolution.

scholarly journals The Influence of Gas Expulsion on the Evolution of Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 36-40
Author(s):  
H. Baumgardt ◽  
P. Kroupa
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Three Dimensional ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Star Cluster ◽  
Dissolution Mechanism ◽  
Large Set ◽  
Cluster Systems

AbstractWe present new results on the dynamical evolution and dissolution of star clusters due to residual gas expulsion and the effect this has on the mass function and other properties of star cluster systems. To this end, we have carried out a large set of N-body simulations, varying the star formation efficiency, gas expulsion time scale and strength of the external tidal field, obtaining a three-dimensional grid of models which can be used to predict the evolution of individual star clusters or whole star cluster systems by interpolating between our runs. When applied to the Milky Way globular cluster system, we find that gas expulsion is the main dissolution mechanism for star clusters, destroying about 80% of all clusters within a few 10s of Myers. Together with later dynamical evolution, it seems possible to turn an initial power-law mass function into a log-normal one with properties similar to what has been observed for the Milky Way globular clusters.

scholarly journals Investigating dynamical properties of evolved Galactic open clusters

2019 ◽  
Vol 624 ◽  
pp. A8 ◽  
Author(s):  
M. S. Angelo ◽  
J. F. C. Santos ◽  
W. J. B. Corradi ◽  
F. F. S. Maia
Keyword(s):  
Open Cluster ◽  
Three Dimensional ◽  
Dynamical Evolution ◽  
Long Term Evolution ◽  
Open Clusters ◽  
Evolutionary Stage ◽  
Proper Motions ◽  
Stellar Content ◽  
Term Evolution

Context. The stellar content of Galactic open clusters is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of open clusters are called open cluster remnants. These are sparsely populated structures that can barely be distinguished from the field. Aims. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as remnants or remnant candidates. We employed parameters that are intimately associated with the dynamical evolution: age, limiting radius, stellar mass, and velocity dispersion. The sample also includes 7 objects that are catalogued as dynamically evolved open clusters for comparison purposes. Methods. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the Gaia DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes (μα, μδ, ϖ) for stars in the objects’ areas. The luminosity and mass functions and total masses for most open cluster remnants are derived here for the first time. Our analysis used predictions of N-body simulations to estimate the initial number of stars of the remnants from their dissolution timescales. Results. The investigated open cluster remnants present masses (M) and velocity dispersions (σv) within well-defined ranges: M between ∼10−40 M⊙ and σv between ∼1−7 km s−1. Some objects in the remnant sample have a limiting radius Rlim ≲ 2 pc, which means that they are more compact than the investigated open clusters; other remnants have Rlim between ∼2−7 pc, which is comparable to the open clusters. We suggest that cluster NGC 2180 (previously classified as an open cluster) is entering a remnant evolutionary stage. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Conclusions. We conclude that the open cluster remnants we studied are in fact remnants of initially very populous open clusters (N0 ∼ 103−104 stars). The outcome of the long-term evolution is to bring the final residues of the open clusters to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.

scholarly journals Early dynamical evolution of star cluster systems

2009 ◽  
Vol 5 (S266) ◽  
pp. 87-94
Author(s):  
Geneviève Parmentier
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Environmental Conditions ◽  
Cluster Formation ◽  
Formation Rate ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Star Cluster ◽  
Dynamical Response ◽  
Cluster Systems

AbstractViolent relaxation, the protocluster dynamical response to the expulsion of its residual star-forming gas, is a short albeit crucial episode in the evolution of star clusters and star cluster systems. Because it is heavily driven by cluster-formation and environmental conditions, it is a potentially highly rewarding phase in terms of probing star formation and galaxy evolution. In this contribution, I review how cluster-formation and environmental conditions affect the shape of the young cluster mass function and the relation between the present star-formation rate of galaxies and the mass of their young, most massive cluster.

scholarly journals On the Origin of Complex Stellar Populations in Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 71-72
Author(s):  
J. Pflamm-Altenburg ◽  
P. Kroupa
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Massive Star ◽  
Cluster Formation ◽  
Star Clusters ◽  
Stellar Populations ◽  
Star Cluster ◽  
Young Stars

AbstractThe existence of complex stellar populations in some star clusters challenges the understanding of star formation. E.g. the ONC or the sigma Orionis cluster host much older stars than the main bulk of the young stars. Massive star clusters (ω Cen, G1, M54) show metallicity spreads corresponding to different stellar populations with large age gaps. We show that (i) during star cluster formation field stars can be captured and (ii) very massive globular clusters can accrete gas from a long-term embedding inter stellar medium and restart star formation.

scholarly journals Dynamical evolution of multiple-population globular clusters

2021 ◽  
Vol 502 (3) ◽  
pp. 4290-4304
Author(s):  
Enrico Vesperini ◽  
Jongsuk Hong ◽  
Mirek Giersz ◽  
Arkadiusz Hypki
Keyword(s):  
Structural Properties ◽  
Globular Clusters ◽  
First Generation ◽  
Radial Profile ◽  
Dynamical Evolution ◽  
Evolutionary Phase ◽  
Dynamical Parameters ◽  
Energy Equipartition

ABSTRACT We have carried out a set of Monte Carlo simulations to study a number of fundamental aspects of the dynamical evolution of multiple stellar populations in globular clusters with different initial masses, fractions of second generation (2G) stars, and structural properties. Our simulations explore and elucidate: (1) the role of early and long-term dynamical processes and stellar escape in the evolution of the fraction of 2G stars and the link between the evolution of the fraction of 2G stars and various dynamical parameters; (2) the link between the fraction of 2G stars inside the cluster and in the population of escaping stars during a cluster’s dynamical evolution; (3) the dynamics of the spatial mixing of the first-generation (1G) and 2G stars and the details of the structural properties of the two populations as they evolve toward mixing; (4) the implications of the initial differences between the spatial distribution of 1G and 2G stars for the evolution of the anisotropy in the velocity distribution and the expected radial profile of the 1G and 2G anisotropy for clusters at different stages of their dynamical history; and (5) the variation of the degree of energy equipartition of the 1G and the 2G populations as a function of the distance from the cluster’s centre and the cluster’s evolutionary phase.

scholarly journals Dynamics of Globular Cluster Systems

1983 ◽  
Vol 100 ◽  
pp. 359-364
Author(s):  
K. C. Freeman
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Cluster Formation ◽  
Active Phase ◽  
Chemical Abundance ◽  
Cluster Systems ◽  
Chemical Enrichment ◽  
Wide Range ◽  
The Galaxy

In the Milky Way, the globular clusters are all very old, and we are accustomed to think of them as the oldest objects in the Galaxy. The clusters cover a wide range of chemical abundance, from near solar down to about [Fe/H] ⋍ −2.3. However there are field stars with abundances significantly lower than −2.3 (eg Bond, 1980); this implies that the clusters formed during the active phase of chemical enrichment, with cluster formation beginning at a time when the enrichment processes were already well under way.

scholarly journals Observational Constraints on the Formation and Evolution of Globular Cluster Systems

2007 ◽  
Vol 3 (S246) ◽  
pp. 394-402
Author(s):  
Stephen E. Zepf
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Cluster System ◽  
Host Galaxy ◽  
Cluster Systems ◽  
Cluster Mass ◽  
Formation And Evolution ◽  
Globular Cluster System

AbstractThis paper reviews some of the observational properties of globular cluster systems, with a particular focus on those that constrain and inform models of the formation and dynamical evolution of globular cluster systems. I first discuss the observational determination of the globular cluster luminosity and mass function. I show results from new very deep HST data on the M87 globular cluster system, and discuss how these constrain models of evaporation and the dynamical evolution of globular clusters. The second subject of this review is the question of how to account for the observed constancy of the globular cluster mass function with distance from the center of the host galaxy. The problem is that a radial trend is expected for isotropic cluster orbits, and while the orbits are observed to be roughly isotropic, no radial trend in the globular cluster system is observed. I review three extant proposals to account for this, and discuss observations and calculations that might determine which of these is most correct. The final subject is the origin of the very weak mass-radius relation observed for globular clusters. I discuss how this strongly constrains how globular clusters form and evolve. I also note that the only viable current proposal to account for the observed weak mass-radius relation naturally effects the globular cluster mass function, and that these two problems may be closely related.

The range of UV upturn strengths in early-type galaxies can be caused by dissolved metal-rich Globular Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 112-116
Author(s):  
Paul Goudfrooij
Keyword(s):  
Globular Clusters ◽  
Dynamical Evolution ◽  
Virgo Cluster ◽  
Host Galaxy ◽  
Early Type ◽  
Luminosity Functions ◽  
Central Regions ◽  
Specific Frequency ◽  
Uv Upturn

AbstractI summarize the scenario by Goudfrooij (2018) in which the bulk of the ultraviolet (UV) upturn of giant early-type galaxies (ETGs) is due to helium-rich stellar populations that formed in massive metal-rich globular clusters (GCs) and subsequently dissolved in the strong tidal field in the central regions of the massive host galaxy. These massive GCs are assumed to show UV upturns similar to those observed recently in M87, the central galaxy in the Virgo cluster of galaxies. Data taken from the literature reveals a strong correlation between the strength of the UV upturn and the specific frequency of metal-rich GCs in ETGs. Adopting a Schechter function parametrization of GC mass functions, simulations of long-term dynamical evolution of GC systems show that this correlation can be explained by variations in the characteristic truncation mass Mc such that Mc increases with ETG luminosity in a way that is consistent with observed GC luminosity functions in ETGs. These findings suggest that the nature of the UV upturn in ETGs and the variation of its strength among ETGs are causally related to that of helium-rich populations in massive GCs, rather than intrinsic properties of field stars in ETGs.

scholarly journals Stellar-mass Black Holes in Globular Clusters: Dynamical consequences and observational signatures

2019 ◽  
Vol 14 (S351) ◽  
pp. 395-399 ◽  
Author(s):  
Abbas Askar ◽  
Mirek Giersz ◽  
Manuel Arca Sedda ◽  
Ammar Askar ◽  
Mario Pasquato ◽  
...  
Keyword(s):  
Black Holes ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Stellar Mass ◽  
Large Set ◽  
Term Survival ◽  
Central Surface ◽  
Sizeable Number ◽  
Hubble Time

AbstractSizeable number of stellar-mass black holes (BHs) in globular clusters (GCs) can strongly influence the dynamical evolution and observational properties of their host cluster. Using results from a large set of numerical simulations, we identify the key ingredients needed to sustain a sizeable population of BHs in GCs up to a Hubble time. We find that while BH natal kick prescriptions are essential in determining the initial retention fraction of BHs in GCs, the long-term survival of BHs is determined by the size, initial central density and half-mass relaxation time of the GC. Simulated GC models that contain many BHs are characterized by relatively low central surface brightness, large half-light and core radii values. We also discuss novel ways to compare simulated results with available observational data to identify GCs that are most likely to contain many BHs.

scholarly journals Open, Massive and Globular Clusters — Part of the Same Family?

2002 ◽  
Vol 207 ◽  
pp. 421-427 ◽  
Author(s):  
Søren S. Larsen
Keyword(s):  
Globular Clusters ◽  
Cluster Formation ◽  
Formation Rate ◽  
Star Clusters ◽  
Young Star ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Cluster Systems ◽  
Physical Description ◽  
Super Star Clusters

Populations of young star clusters show significant differences even among “normal” disk galaxies. In this contribution I discuss how properties of young cluster systems are related to those of their host galaxies, based on a recent study of clusters in a sample of 22 nearby spiral galaxies. Luminous young clusters similar to the “super” star clusters observed in starbursts and mergers exist in several of these galaxies, and it is found that the luminosity of the brightest star cluster as well as the specific luminosity of the cluster systems both correlate well with the host galaxy star formation rate. When considering star clusters in different environments the traditional distinction between “open”, “massive” and “globular” clusters breaks down, underscoring the need for a universal physical description of cluster formation.

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