scholarly journals The effects of a background potential in star cluster evolution

2020 ◽  
Vol 639 ◽  
pp. A92 ◽  
Author(s):  
B. Reinoso ◽  
D. R. G. Schleicher ◽  
M. Fellhauer ◽  
N. W. C. Leigh ◽  
R. S. Klessen
Keyword(s):  
Binary Stars ◽  
Gravitational Force ◽  
Massive Star ◽  
Star Clusters ◽  
Star Cluster ◽  
Early Evolution ◽  
Relaxation Processes ◽  
Blue Stragglers ◽  
Stellar Collisions ◽  
The Universe

Runaway stellar collisions in dense star clusters are invoked to explain the presence of very massive stars or blue stragglers in the center of those systems. This process has also been explored for the first star clusters in the Universe and shown to yield stars that may collapse at some points into an intermediate mass black hole. Although the early evolution of star clusters requires the explicit modeling of the gas out of which the stars form, these calculations would be extremely time-consuming and often the effects of the gas can be accurately treated by including a background potential to account for the extra gravitational force. We apply this approximation to model the early evolution of the first dense star clusters formed in the Universe by performing N-body simulations, our goal is to understand how the additional gravitational force affects the growth of a very massive star through stellar mergers in the central parts of the star cluster. Our results show that the background potential increases the velocities of the stars, causing an overall delay in the evolution of the clusters and in the runaway growth of a massive star at the center. The population of binary stars is lower due to the increased kinetic energy of the stars, initially reducing the number of stellar collisions, and we show that relaxation processes are also affected. Despite these effects, the external potential enhances the mass of the merger product by a factor ∼2 if the collisions are maintained for long times.

scholarly journals Modeling of Integrated Spectral Energy Distributions of Stellar Populations with Various Binary Fractions

2021 ◽  
Vol 2068 (1) ◽  
pp. 012048
Author(s):  
Zhongmu Li ◽  
Chen Yan
Keyword(s):  
Binary Stars ◽  
Star Clusters ◽  
Stellar Populations ◽  
Spectral Studies ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Spectral Fitting ◽  
The Universe

Abstract Binary stars are common in the universe, but binary fractions are various in different star clusters and galaxies. Studies have shown that binary fraction affects the integrated spectral energy distributions obviously, in particular in the UV band. It affects spectral fitting of many star clusters and galaxies significantly. However, previous works usually take a fixed binary fraction, i.e., 0.5, and this is far from getting accurate results. Therefore, it is important to model the integrated spectral energy distributions of stellar populations with various binary fractions. This work presents a modeling of spectral energy distributions of simple stellar populations with binary fractions of 0.3, 0.7, and 1.0. The results are useful for different kinds of spectral studies.

3. Stars

2016 ◽  
pp. 22-49
Author(s):  
James Binney
Keyword(s):  
Star Formation ◽  
20Th Century ◽  
Binary Stars ◽  
Star Clusters ◽  
Solar Neutrinos ◽  
Interstellar Gas ◽  
Stellar Seismology ◽  
Stellar Masses ◽  
Century Science ◽  
The Universe

Most of what we know about the Universe has been gleaned from the study of stars, and a major achievement of 20th-century science was to understand how stars work and their lifecycles from birth to death. ‘Stars’ describes this lifecycle beginning with star formation when a cloud of interstellar gas suffers a runaway of its central density. It then considers nuclear fusion, key stellar masses, and life after the main sequence when the star burns its core helium. The surfaces of stars are described along with stellar coronae and exploding stars—both core-collapse and deflagration supernovae. Finally, globular star clusters, solar neutrinos, stellar seismology, and binary stars are discussed.

scholarly journals Massive star clusters in galaxies

2010 ◽  
Vol 368 (1913) ◽  
pp. 889-906 ◽  
Author(s):  
William E. Harris
Keyword(s):  
Recent Work ◽  
Globular Clusters ◽  
Evolutionary History ◽  
Massive Star ◽  
Star Clusters ◽  
Star Cluster ◽  
Cluster System ◽  
History Of ◽  
Review Current

The ensemble of all star clusters in a galaxy constitutes its star cluster system . In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GC research, and highlight some of the outstanding questions that are emerging from recent work.

scholarly journals On the early evolution of massive star clusters: the case of cloud D1 and its embedded cluster in NGC 5253

2020 ◽  
Vol 494 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Sergiy Silich ◽  
Guillermo Tenorio-Tagle ◽  
Sergio Martínez-González ◽  
Jean Turner
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Star Clusters ◽  
Early Evolution ◽  
Mass Loading ◽  
Low Mass Stars ◽  
Stellar Cluster ◽  
Star Forming ◽  
Cluster Phase ◽  
Protostellar Discs

ABSTRACT We discuss a theoretical model for the early evolution of massive star clusters and confront it with the ALMA, radio, and infrared observations of the young stellar cluster highly obscured by the molecular cloud D1 in the nearby dwarf spheroidal galaxy NGC 5253. We show that a large turbulent pressure in the central zones of D1 cluster may cause individual wind-blown bubbles to reach pressure confinement before encountering their neighbours. In this case, stellar winds energy is added to the hot shocked wind pockets of gas around individual massive stars that leads them to meet and produce a cluster wind in time-scales less than 105 yr. In order to inhibit the possibility of cloud dispersal, or the early negative star formation feedback, one should account for mass loading that may come, for example, from pre-main-sequence (PMS) low-mass stars through photoevaporation of their protostellar discs. Mass loading at a rate in excess of 8 × 10−9 M⊙ yr−1 per each PMS star is required to extend the hidden star cluster phase in this particular cluster. In this regime, the parental cloud remains relatively unperturbed, while pockets of molecular, photoionized and hot gas coexist within the star-forming region. Nevertheless, the most likely scenario for cloud D1 and its embedded cluster is that the hot shocked winds around individual massive stars should merge at an age of a few million of years when the PMS star protostellar discs vanish and mass loading ceases that allows a cluster to form a global wind.

scholarly journals Compact Nuclei of Galaxies and Sources of Their Energy

1999 ◽  
Vol 194 ◽  
pp. 323-323
Author(s):  
L.Sh. Grigoryan ◽  
G.S. Sahakian
Keyword(s):  
Equation Of State ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Star Cluster ◽  
Statistical Equilibrium ◽  
Spherically Symmetric ◽  
Symmetric Star ◽  
Age Of The Universe ◽  
The Universe

A model of compact nuclei of galaxies as spherically-symmetric star clusters is proposed. A concept of the equation of state for star clusters in statistical equilibrium is introduced (galactic nuclei are systems in statistical equilibrium if their age is of the order of the age of the Universe). It is shown that a statistically equilibrium star cluster is described by the equation of state of a polytrope P = aρ3, and with its help the main parameters of compact nuclei of galaxies are calculated. The formula M = 2.524GR5/a for mass M and radius R of the cluster is derived.

scholarly journals Massive star cluster formation and evolution in tidal dwarf galaxies

2019 ◽  
Vol 628 ◽  
pp. A60 ◽  
Author(s):  
Jérémy Fensch ◽  
Pierre-Alain Duc ◽  
Médéric Boquien ◽  
Debra M. Elmegreen ◽  
Bruce G. Elmegreen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Cluster Formation ◽  
Spectral Energy Distribution ◽  
Star Clusters ◽  
Star Cluster ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Near Ultraviolet

Context. The formation of globular clusters remains an open debate. Dwarf starburst galaxies are efficient at forming young massive clusters with similar masses as globular clusters and may hold the key to understanding their formation. Aims. We study star cluster formation in a tidal debris, including the vicinity of three tidal dwarf galaxies, in a massive gas-dominated collisional ring around NGC 5291. These dwarfs have physical parameters that differ significantly from local starbursting dwarfs. They are gas rich, highly turbulent, their gas metallicity is already enriched up to half solar values, and they are expected to be free of dark matter. The aim is to study massive star cluster formation in this as yet unexplored type of environment. Methods. We used imaging from the Hubble Space Telescope using broadband filters that cover the wavelength range from the near-ultraviolet to the near-infrared. We determined the masses and ages of the cluster candidates by using the spectral energy distribution-fitting code CIGALE. We considered age-extinction degeneracy effects on the estimation of the physical parameters. Results. We find that the tidal dwarf galaxies in the ring of NGC 5291 are forming star clusters with an average efficiency of ∼40%, which is similar to blue compact dwarf galaxies. We also find massive star clusters for which the photometry suggests that they were formed at the very birth of the tidal dwarf galaxies. These clusters have survived for several hundred million years. Therefore our study shows that extended tidal dwarf galaxies and compact clusters may be formed simultaneously. In the specific case observed here, the young star clusters are not massive enough to survive for a Hubble time. However, it may be speculated that similar objects at higher redshift, with a higher star formation rate, might form some of the long-lived globular clusters.

scholarly journals Effects of Stellar Collisions on Star Cluster Evolution and Core Collapse

2007 ◽  
Vol 3 (S246) ◽  
pp. 151-155 ◽  
Author(s):  
Sourav Chatterjee ◽  
John M. Fregeau ◽  
Frederic A. Rasio
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Massive Stars ◽  
Relaxation Times ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Star Cluster ◽  
Core Collapse ◽  
Cluster Evolution ◽  
Stellar Collisions

AbstractWe systematically study the effects of collisions on the overall dynamical evolution of dense star clusters using Monte Carlo simulations over many relaxation times. We derive many observable properties of these clusters, including their core radii and the radial distribution of collision products. We also study different aspects of collisions in a cluster taking into account the shorter lifetimes of more massive stars, which has not been studied in detail before. Depending on the lifetimes of the significantly more massive collision products, observable properties of the cluster can be modified qualitatively; for example, even without binaries, core collapse can sometimes be avoided simply because of stellar collisions.

scholarly journals Super star clusters in Hii galaxies

2009 ◽  
Vol 5 (S266) ◽  
pp. 447-450
Author(s):  
Patricio Lagos ◽  
Eduardo Telles ◽  
E. R. Carrasco
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Massive Star ◽  
Star Clusters ◽  
Dominant Mode ◽  
Star Cluster ◽  
The Galaxy ◽  
Super Star Clusters ◽  
Field Unit ◽  
The Masses

AbstractWe summarize our results based on observations with the NIRI camera on the Gemini North telescope of three Hii galaxies (Mrk 36, UM 408 and UM 461), obtained to identify and determine the ages and masses of the elementary components (the star cluster population) of the starburst regions in compact Hii galaxies. Our preliminary results indicate that the masses of the stellar clusters in these galaxies range from ~104 to ~106 M⊙, with associated ages of a few Myr. The most massive star clusters fall in the so-called super star cluster category. The identification of these clusters suggests that the formation and evolution of massive star clusters is the dominant mode of star formation in these galaxies. Their spatial distribution and ages seem to indicate that star formation is simultaneous over these timescales in some of our objects. We also review our recent description of the spatial distribution of physical conditions in the Hii galaxy UM 408 using the GMOS integral-field unit on Gemini South. The spatial distribution of the oxygen abundance does not show any significant variation or gradient across the galaxy on scales of hundreds of parsecs, within our observational uncertainties, confirming that this compact Hii galaxy, like other previously studied dwarf irregular galaxies, is chemically homogeneous.

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