scholarly journals Photographic Photometry With Schmidt Plates of Star Clusters in the SMC

1984 ◽  
Vol 78 ◽  
pp. 355-357
Author(s):  
M. Kontizas
Keyword(s):  
Stellar Evolution ◽  
Initial Conditions ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Large Field ◽  
Stellar Systems ◽  
Nearest Neighbour ◽  
Photographic Photometry

The star clusters have always been the most important tools of testing the stellar evolution theories and when these stellar systems belong to other galaxies, then our knowledge on stellar evolution can be extended for different initial conditions than those of our Galaxy. The Magellanic Clouds being our nearest neighbour galaxies offer ideal conditions for such studies.Since the powerful southern telescope came into operation deep plates of these two galaxies revealed a large number of new star clusters. The Schmidt plates are most useful since they have the advantage of large field where many objects can be investigated homogeneously on the same plate.

scholarly journals Magellanic globulars as cosmological tools

1991 ◽  
Vol 148 ◽  
pp. 165-169
Author(s):  
Alvio Renzini
Keyword(s):  
Galaxy Formation ◽  
Stellar Evolution ◽  
Globular Clusters ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Range ◽  
Magellanic Clouds ◽  
Evolution Theory ◽  
Mass Functions ◽  
The Ideal

The globular clusters (GC) of the Magellanic Clouds play a very important role for many astrophysical and cosmological topics. For example, they represent the ideal testground for stellar evolution theory, they allow us to study the the early dynamical evolution of star clusters, to obtain accurate initial mass functions in a fairly extended mass range, to calibrate the Cepheid period-luminosity relation, and so on. In this brief paper I will touch upon two items which are of considerable cosmological interest, and about which Magellanic Cloud globulars provide unique information. These topics concern i) GC formation in galaxies, and ii) the epoch of galaxy formation.

scholarly journals The star clusters of the Magellanic Clouds

2008 ◽  
Vol 4 (S258) ◽  
pp. 275-286
Author(s):  
A. D. Mackey
Keyword(s):  
Stellar Evolution ◽  
Stellar Population ◽  
Star Clusters ◽  
Population Models ◽  
Magellanic Clouds ◽  
Individual Stars ◽  
Wide Range ◽  
Metal Abundance ◽  
Formation And Evolution ◽  
Astronomical Research

AbstractThe Magellanic Clouds possess extensive systems of rich star clusters. These objects span a wide range in age and metal abundance, and are close enough to be fully resolved into individual stars. They represent the most accessible examples of such clusters and are therefore key to a wide variety of astronomical research. In this contribution I describe recent results from work on several problems in Magellanic Cloud cluster astronomy of relevance to The Ages of Stars. These include testing and constraining stellar evolution and simple stellar population models, investigating the formation and evolution of the Clouds themselves, and the discovery of several intermediate-age clusters which apparently possess more than one stellar population.

scholarly journals Initial conditions of formation of starburst clusters: constraints from stellar dynamics

2015 ◽  
Vol 12 (S316) ◽  
pp. 228-233
Author(s):  
Sambaran Banerjee
Keyword(s):  
Molecular Clouds ◽  
Massive Star ◽  
Initial Conditions ◽  
Star Clusters ◽  
Stellar Dynamics ◽  
Stellar Systems ◽  
Residual Gas ◽  
Open Question ◽  
Massive Clusters

AbstractHow starburst clusters form out of molecular clouds is still an open question. In this article, I highlight some of the key constraints in this regard, that one can get from the dynamical evolutionary properties of dense stellar systems. I particularly focus on secular expansion of massive star clusters and hierarchical merging of sub-clusters, and discuss their implicationsvis-á-visthe observed properties of young massive clusters. The analysis suggests that residual gas expulsion is necessary for shaping these clusters as we see them today, irrespective of their monolithic or hierarchical mode of formation.

scholarly journals Dynamical evolution of population III stellar systems and the resulting binary statistics

2020 ◽  
Vol 501 (1) ◽  
pp. 643-663
Author(s):  
Boyuan Liu ◽  
Georges Meynet ◽  
Volker Bromm
Keyword(s):  
Initial Conditions ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Initial Mass Function ◽  
Close Binary ◽  
Close Binaries ◽  
Small Scale ◽  
Stellar Systems ◽  
X Ray ◽  
Population Iii

ABSTRACT We use N-body simulations to study the dynamical evolution of population III (Pop III) stellar systems and the resulting binary statistics. We design a physically motivated framework for the initial conditions of Pop III star clusters, based on small-scale hydrodynamic simulations and the scale-free nature of disc evolution during Pop III star formation. Our novel approach enables us to explore the dependence of binary statistics on initial conditions and arrive at more robust predictions for the signals of Pop III X-ray binaries (XRBs) and binary black hole (BBH) mergers, compared to simple extrapolations of Pop III protostar systems. We find that binary properties are highly sensitive to the initial cluster size and distribution of binary separation, while the effect of initial mass function is relatively minor. Our simulations predict less close binaries, and thus, significantly lower efficiencies (by a factor of ∼10–104) for the formation and accretion of Pop III XRBs, than found in previous studies, implying that the contribution of Pop III XRBs to the cosmic X-ray background is negligible and their feedback effects are unimportant. We estimate the efficiency of Pop III BBH mergers as $\sim 10^{-5}\!-\!10^{-4}\ \rm M_{\odot }^{-1}$, for which three-body hardening by surrounding stars in dense star clusters or close binary interactions is required to facilitate in-spirals of BBHs. All simulation data, including catalogues of Pop III binaries and multiple systems, are publicly available.

scholarly journals Black Holes and Core Expansion in Massive Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 176-180
Author(s):  
A. D. Mackey ◽  
M. I. Wilkinson ◽  
M. B. Davies ◽  
G. F. Gilmore
Keyword(s):  
Black Holes ◽  
Stellar Evolution ◽  
Massive Star ◽  
Massive Stars ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Core Radius ◽  
Stellar Component ◽  
Rapid Mass ◽  
Dynamical Origin

AbstractMassive star clusters in the Magellanic Clouds are observed to follow a striking trend in size with age – older clusters exhibit a much greater spread in core radius than do younger clusters, which are generally compact. We present results from realistic N-body modelling of massive star clusters, aimed at investigating a dynamical origin for the radius-age trend. We find that stellar-mass black holes, formed as remnants of the most massive stars in a cluster, can constitute a dynamically important population. If retained, these objects rapidly form a dense core where interactions are common, resulting in the scattering of black holes into the cluster halo, and the ejection of black holes from the cluster. These processes heat the stellar component, resulting in prolonged core expansion of a magnitude matching the observations. Core expansion at early times does not result from the action of black holes, but can be reproduced by the effects of rapid mass-loss due to stellar evolution in a primordially mass segregated cluster.

scholarly journals Photometric studies of composite stellar systems. V - Infrared photometry of star clusters in the Magellanic clouds

1983 ◽  
Vol 266 ◽  
pp. 105 ◽  
Author(s):  
S. E. Persson ◽  
M. Aaronson ◽  
J. G. Cohen ◽  
J. A. Frogel ◽  
K. Matthews
Keyword(s):  
Star Clusters ◽  
Magellanic Clouds ◽  
Stellar Systems ◽  
Infrared Photometry

scholarly journals Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions

2021 ◽  
Author(s):  
Arpan Das ◽  
Dominik R G Schleicher ◽  
Nathan W C Leigh ◽  
Tjarda C N Boekholt
Keyword(s):  
Black Holes ◽  
Initial Conditions ◽  
High Redshift ◽  
Star Clusters ◽  
Gas Reservoir ◽  
Highly Sensitive ◽  
Stellar Collisions ◽  
Key Variables ◽  
Chaotic Nature ◽  
Gas Accretion

Abstract More than two hundred supermassive black holes (SMBHs) of masses ≳ 109 M⊙ have been discovered at z ≳ 6. One promising pathway for the formation of SMBHs is through the collapse of supermassive stars (SMSs) with masses ∼103 − 5 M⊙ into seed black holes which could grow upto few times 109 M⊙ SMBHs observed at z ∼ 7. In this paper, we explore how SMSs with masses ∼103 − 5 M⊙ could be formed via gas accretion and runaway stellar collisions in high-redshift, metal-poor nuclear star clusters (NSCs) using idealised N-body simulations. We explore physically motivated accretion scenarios, e.g. Bondi-Hoyle-Lyttleton accretion and Eddington accretion, as well as simplified scenarios such as constant accretions. While gas is present, the accretion timescale remains considerably shorter than the timescale for collisions with the most massive object (MMO). However, overall the timescale for collisions between any two stars in the cluster can become comparable or shorter than the accretion timescale, hence collisions still play a crucial role in determining the final mass of the SMSs. We find that the problem is highly sensitive to the initial conditions and our assumed recipe for the accretion, due to the highly chaotic nature of the problem. The key variables that determine the mass growth mechanism are the mass of the MMO and the gas reservoir that is available for the accretion. Depending on different conditions, SMSs of masses ∼103 − 5 M⊙ can form for all three accretion scenarios considered in this work.

scholarly journals Ages of Galactic and Extragalactic Star Clusters of Various Abundances

1983 ◽  
Vol 6 ◽  
pp. 109-117 ◽  
Author(s):  
R.D. Cannon
Keyword(s):  
Star Clusters ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Simultaneous Solution ◽  
Low Mass Stars ◽  
Cluster Systems ◽  
Distant Cluster ◽  
Low Mass

In this review I shall concentrate mainly on globular star clusters in our Galaxy since these are the objects for which most work has been done recently, both observationally and theoretically. However, I shall also discuss briefly the oldest open clusters and clusters in the Magellanic Clouds. Little can be said about more distant cluster systems, since the only observations available are of integrated colours or spectra and these seem to be rather unreliable indicators of age. It is perhaps worth pointing out that the title may be slightly misleading; the problem is not so much to determine the ages of clusters of known abundances, as to obtain the best simultaneous solution for both age and composition, since some of the most important abundances (notably helium and oxygen) are virtually unobservable in little-evolved low mass stars.

scholarly journals Populations of OB-type stars in galaxies

2010 ◽  
Vol 6 (S272) ◽  
pp. 233-241
Author(s):  
Christopher J. Evans
Keyword(s):  
Stellar Evolution ◽  
Massive Stars ◽  
Spectral Synthesis ◽  
High Redshift ◽  
Young Star ◽  
Magellanic Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
External Galaxies

AbstractOne of the challenges for stellar astrophysics is to reach the point at which we can undertake reliable spectral synthesis of unresolved populations in young, star-forming galaxies at high redshift. Here I summarise recent studies of massive stars in the Galaxy and Magellanic Clouds, which span a range of metallicities commensurate with those in high-redshift systems, thus providing an excellent laboratory in which to study the role of environment on stellar evolution. I also give an overview of observations of luminous supergiants in external galaxies out to a remarkable 6.7 Mpc, in which we can exploit our understanding of stellar evolution to study the chemistry and dynamics of the host systems.

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