scholarly journals The life and death of star clusters

2006 ◽  
Vol 2 (S237) ◽  
pp. 222-229 ◽  
Author(s):  
B. C. Whitmore
Keyword(s):  
Massive Star ◽  
Cluster Formation ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Merging Galaxies ◽  
Life And Death ◽  
Large Numbers ◽  
Super Star Clusters ◽  
Massive Clusters

AbstractIt is generally believed that most stars are born in groups and clusters, rather than in the field. It has also been demonstrated that merging galaxies produce large numbers of young massive star clusters, sometimes called super star clusters. Hence, understanding what triggers the formation of these young massive clusters may provide important information about what triggers the formation of stars in general. In recent years it has become apparent that most clusters do not survive more than ≈10 Myr (i.e., “infant mortality”). Hence, it is just as important to understand the disruption of star clusters as it is to understand their formation if we want to understand the demographics of both star clusters and field stars. This talk will first discuss what triggers star cluster formation in merging galaxies (primarily in the Antennae galaxies), will then demonstrate that most of the faint objects detected in the Antennae are clusters rather than individual stars (which shows that the initial mass function was a power law rather than a Gaussian), and will then outline a general framework designed to empirically fit observations of both star clusters and field stars in a wide variety of galaxies from mergers to quiescent spirals.

scholarly journals The massive star Initial Mass function

2003 ◽  
Vol 212 ◽  
pp. 642-651 ◽  
Author(s):  
Daniel Schaerer
Keyword(s):  
Massive Star ◽  
Current Knowledge ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
H Ii Regions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Super Star Clusters ◽  
The Imf

We review our current knowledge on the IMF in nearby environments, massive star forming regions, super star clusters, starbursts and alike objects from studies of integrated light, and discuss the various techniques used to constrain the IMF. In most cases, including UV-optical studies of stellar features and optical-IR analysis of nebular emission, the data is found to be compatible with a ‘universal’ Salpeter-like IMF with a high upper mass cut-off over a large metallicity range. In contrast, near-IR observations of nuclear starbursts and LIRG show indications of a lowerMupand/or a steeper IMF slope, for which no alternate explanation has yet been found. Also, dynamical mass measurements of seven super star clusters provide so far no simple picture of the IMF. Finally, we present recent results of a direct stellar probe of the upper end of the IMF in metal-rich H ii regions, showing no deficiency of massive stars at high metallicity, and determining a lower limit ofMup≳ 60 – 90 M⊙.

scholarly journals Mid-infrared [NeII] Imaging of Young Massive Star Clusters Near Galactic Nuclei

2015 ◽  
Vol 12 (S316) ◽  
pp. 161-162
Author(s):  
Sherry C. C. Yeh ◽  
Chao-Wei Tsai ◽  
Thomas R. Geballe ◽  
Cinthya N. Herrera
Keyword(s):  
Environmental Effects ◽  
Massive Star ◽  
Cluster Formation ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Mass Function ◽  
Mid Infrared ◽  
Ngc 6946 ◽  
Formation Efficiency ◽  
Massive Clusters

AbstractWe investigate the formation of young massive clusters near the nuclei in NGC 6946, IC 342, Maffei II, and NGC 7714, using ground-based mid-infrared [NeII] imaging. We derive the cluster formation efficiency and cluster mass function, and the results suggest that environmental effects on YMC formation may not be significant.

scholarly journals Young massive star clusters: achievements and challenges

2009 ◽  
Vol 5 (S266) ◽  
pp. 49-57 ◽  
Author(s):  
Richard de Grijs
Keyword(s):  
Massive Star ◽  
Initial Conditions ◽  
Cluster Formation ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Ongoing Research ◽  
Mass Segregation

AbstractIn spite of significant recent and ongoing research efforts, most of the early evolution and long-term fate of young massive star clusters remain clouded in uncertainties. Here, I discuss our understanding of the initial conditions of star cluster formation and the importance of initial substructure for the subsequent dynamical-evolution and mass-segregation timescales. I also assess our current understanding of the (initial) binary fraction in star clusters and the shape of the stellar initial mass function at the low-mass end in the low-metallicity environment of the Large Magellanic Cloud. Finally, I question the validity of our assumptions leading to dynamical cluster mass estimates. I conclude that it seems imperative that observers, modellers and theorists combine efforts and exchange ideas and data freely for the field to make a major leap forward.

scholarly journals Super star clusters in the Galactic Center as revealed by HST-NICMOS

1999 ◽  
Vol 193 ◽  
pp. 459-469
Author(s):  
Donald F. Figer ◽  
Sungsoo S. Kim ◽  
Mark Morris ◽  
Eugene Serabyn
Keyword(s):  
Main Sequence ◽  
Local Group ◽  
Galactic Center ◽  
Formation Rate ◽  
Star Clusters ◽  
Initial Mass Function ◽  
Stellar Content ◽  
Multiple Star ◽  
Super Star Clusters ◽  
Massive Clusters

The three massive clusters in the Galactic Center are not only the most massive young clusters in the Galaxy, but they harbor more Wolf-Rayet stars than any other starburst region in the Local Group. An understanding of their stellar content will be valuable for extending models to starburst regions in other galaxies. We present HST-NICMOS images, luminosity functions, and color-magnitude diagrams of two of these: the Quintuplet and Arches clusters. The images allow the detection of stars over 6 magnitudes fainter than ever before and reveal previously undetected multiple star systems. For the first time, we clearly identify the main sequence in the Quintuplet cluster, and we extend earlier detections of the main sequence in the Arches cluster to Minitial < 10 M⊙. We estimate that the Arches cluster has an initial mass function slope which is greater than the Salpeter value. Given their stellar content, the Galactic Center clusters provide both the best nearby examples of super star clusters and the best nearby locale in which to investigate WR phenomena in starburst galaxies and galactic nuclei. We discuss the content of the Galactic Center clusters, with a particular emphasis on how they compare to other massive clusters of the local group. We expect that many of the massive stars in the Galactic Center will soon evolve to become WR stars, and eventually become supernovae at a rate of ∼ 1 per 20 000 years for the next several Myr. We note that our preliminary N-body simulations suggest that such dense clusters are short-lived in the strong tidal field of the Galactic Center, consistent with the fact that no older dense clusters are seen in the central 50 pc. This implies a star formation rate of 5(10−3) M⊙ yr−1 in the Galactic Center.

scholarly journals Global survey of star clusters in the Milky Way

2018 ◽  
Vol 614 ◽  
pp. A22 ◽  
Author(s):  
A. E. Piskunov ◽  
A. Just ◽  
N. V. Kharchenko ◽  
P. Berczik ◽  
R.-D. Scholz ◽  
...  
Keyword(s):  
Milky Way ◽  
Cluster Formation ◽  
Formation Rate ◽  
Age Distribution ◽  
Star Clusters ◽  
Mass Function ◽  
Spatial Variations ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Formation History

Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.

scholarly journals Modeling of cosmic ray 22Ne-enrichment in compact star clusters

2021 ◽  
Vol 2103 (1) ◽  
pp. 012008
Author(s):  
M E Kalyashova ◽  
A M Bykov
Keyword(s):  
Massive Star ◽  
Isotopic Ratio ◽  
Compact Star ◽  
Star Clusters ◽  
Cosmic Ray ◽  
Rotation Velocity ◽  
Mass Function ◽  
Galactic Cosmic Rays ◽  
Initial Mass Function ◽  
The Impact

Abstract 22Ne/20Ne isotopic ratio is found to be about 5 times higher in Galactic cosmic rays (GCRs) than in the solar wind. In this paper we develop the hypothesis that the 22Ne overabundance in CRs is generated in compact massive star clusters which contain populations of Wolf-Rayet stars. Winds of Wolf-Rayet stars are considered to have high content of 22Ne. We assume that particle acceleration occurs on the ensemble of strong shocks from the massive stars’ winds. We present a model of cosmic ray enrichment with 22Ne, adding isotopic yields from supernovae and taking into account the acceleration efficiency during the lifetime of the stars. The impact of the parameters (the initial mass function in the cluster, rotation velocity, black hole cut-off mass) is discussed. The energy balance for our model is calculated.

scholarly journals Synthesis models for starburst populations with Wolf-Rayet stars

1999 ◽  
Vol 193 ◽  
pp. 526-538 ◽  
Author(s):  
Claus Leitherer
Keyword(s):  
Stellar Population ◽  
Star Clusters ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Stellar Content ◽  
Single Star ◽  
Current State ◽  
Formation History ◽  
Super Star Clusters

The prospects of utilizing Wolf-Rayet populations in starburst galaxies to infer the stellar content are reviewed. I discuss which WR star features can be detected in an integrated stellar population. Specific examples are given where the presence of WR stars can help understand galaxy properties independent of the O-type star population. I demonstrate how populations with small age spread, such as super star clusters, permit observational tests to distinguish between single-star and binary models to produce WR stars. Different synthesis models for WR populations are compared. Predictions for WR properties vary dramatically between individual models. The current state of the models is such that a comparison with starburst populations is more useful for improving WR atmosphere and evolution models than for deriving the star-formation history and the initial mass function.

scholarly journals The star clusters of the Magellanic System

2008 ◽  
Vol 4 (S256) ◽  
pp. 69-80
Author(s):  
Basílio X. Santiago
Keyword(s):  
Mass Loss ◽  
Cluster Formation ◽  
Formation Rate ◽  
Star Clusters ◽  
Mass Range ◽  
Mass Function ◽  
Cluster System ◽  
Initial Mass Function ◽  
Sequence Evolution ◽  
Chemical Abundance

AbstractMore than 50 years have elapsed since the first studies of star clusters in the Magellanic Clouds. The wealth of data accumulated since then has not only revealed a large cluster system, but also a diversified one, filling loci in the age, mass and chemical abundance parameter space which are complementary to Galactic clusters. Catalogs and photometric samples currently available cover most of the cluster mass range. The expectations of relatively long cluster disruption timescales in the Clouds have been confirmed, allowing reliable assessments of the cluster initial mass function and of the cluster formation rate in the Clouds. Due to their proximity to the Galaxy, Magellanic clusters are also well resolved into stars. Analysis of colour—magnitude diagrams (CMDs) of clusters with different ages, masses and metallicities are useful tools to test dynamical effects such as mass loss due to stellar evolution, two-body relaxation, stellar evaporation, cluster interactions and tidal effects. The existence of massive and young Magellanic clusters has provided insight into the physics of cluster formation. The magnitudes and colours of different stellar types are confronted with stellar evolutionary tracks, thus constraining processes such as convective overshooting, stellar mass-loss, rotation and pre main-sequence evolution. Finally, the Magellanic cluster system may contribute with nearby and well studied counterparts of recently proposed types of extragalactic clusters, such as Faint Fuzzies and Diffuse Star Clusters.

scholarly journals “Super” Star Clusters

2005 ◽  
Vol 13 ◽  
pp. 363-365
Author(s):  
Richard de Grijs
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Compact Star ◽  
Cluster Formation ◽  
Survival Rates ◽  
Extreme Environments ◽  
Star Clusters ◽  
Building Blocks ◽  
Initial Mass Function ◽  
Super Star Clusters

AbstractThe production of “super star clusters” (SSCs; luminous, compact star clusters) seems to be a hallmark of intense star formation, particularly in interacting and star-burst galaxies. Their sizes, luminosities, and mass estimates are entirely consistent with what is expected for young Milky Way-type globular clusters (GCs). SSCs are important because of what they can tell us about GC formation and evolution (e.g., initial characteristics and early survival rates). They are also of prime importance as probes of the formation and (chemical) evolution of their host galaxies, and of the initial mass function in the extreme environments required for cluster formation. Recent evidence lends support to the scenario that Milky Way-type GCs (although more metal rich), which were once thought to be the oldest building blocks of galaxies, are still forming today.

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