scholarly journals The e-MERLIN Cyg OB2 radio survey (COBRaS)

2010 ◽  
Vol 6 (S272) ◽  
pp. 306-307
Author(s):  
Raman K. Prinja ◽  
Danielle Fenech
Keyword(s):  
Thermal Radiation ◽  
Mass Loss ◽  
Northern Hemisphere ◽  
Globular Clusters ◽  
Massive Stars ◽  
Star Clusters ◽  
Formation Dynamics ◽  
Super Star Clusters ◽  
Massive Clusters ◽  
Radio Survey

AbstractThe e-MERLIN Cyg OB2 Radio Survey (COBRaS) is designed to exploit e-MERLIN's enhanced capabilities to conduct uniquely probing, targeted deep-field mapping of the massive Cyg OB2 association in our Galaxy. The project aims to deliver (between 2010 to 2013) the most detailed radio census for the most massive OB association in the northern hemisphere, offering direct comparison to not only massive clusters in general, but also young globular clusters and super star clusters. With the COBRaS Legacy project we will assemble a uniform dataset of lasting value that is critical for advancing our understanding of current astrophysical problems in the inter-related core themes of (i) mass loss and evolution of massive stars, (ii) the formation, dynamics and content of massive OB associations, and (iii) the frequency of massive binaries and the incidence of non-thermal radiation.

Super star clusters and their multiple stellar populations

2019 ◽  
Vol 14 (S351) ◽  
pp. 350-353
Author(s):  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Massive Stars ◽  
Characteristic Temperature ◽  
Star Clusters ◽  
Potential Wells ◽  
Low Mass ◽  
New Feature ◽  
Chemical Anomalies ◽  
Super Star Clusters

AbstractWe present a scenario for the formation of super star clusters (with masses larger than 105 M⊙) in which multiple generations of star formation will occur. We stress that the gas left over (∼50%) from first generation (1G) star formation should be retained in such massive clusters (thanks to their deep potential wells, with escape speeds larger than 10 km/s) and be available for a second or even third generation of stars, with the basic HeCNONaMgAl chemical anomalies observed in globular clusters, the latter assumed to be the descendents of these super star clusters. One new feature of this model is the role of C+ cooling of the dense warm trapped neutral or ionized gas which defines a characteristic temperature of ∼100 K, leading to a second generation (2G) of stars with a top-heavy IMF (M > 5 M⊙). The ashes of the 2G very massive stars (VMS, M > 100 M⊙) sampled in this IMF quickly pollute and dilute the left-over pristine gas with their slow winds (that cannot escape the cluster), while the majority of massive stars develop fast winds (that actually can escape from the cluster). Meanwhile, much of the remaining dense T = 100 K gas contracts gravitationally in the massive cluster and may reach densities of the order of 109 cm−3, in which case the Jeans mass drops to about 0.2 M⊙ and leads to a substantial low-mass pre-MS 3G population (most likely on a very short timescale). In this way, we may solve both the mass budget and the excess Helium problem in proto-globular clusters, while also explaining the Na-O and Mg-Al anti-correlations resulting from hot H-burning of very massive stars at 45MK and 75MK, respectively.

scholarly journals The accreted nuclear clusters of the Milky Way

2020 ◽  
Vol 500 (2) ◽  
pp. 2514-2524
Author(s):  
Joel Pfeffer ◽  
Carmela Lardo ◽  
Nate Bastian ◽  
Sara Saracino ◽  
Sebastian Kamann
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Host Galaxy ◽  
The Galaxy ◽  
Nuclear Clusters ◽  
The Common ◽  
Massive Clusters ◽  
Peculiar Case

ABSTRACT A number of the massive clusters in the halo, bulge, and disc of the Galaxy are not genuine globular clusters (GCs) but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs and can be readily traced back to their host galaxy (e.g. M54 and the Sagittarius Dwarf galaxy), others have proven more elusive. Here, we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, ω Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken, and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate-mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster–cluster merger.

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.

scholarly journals The influence of feedback from massive stars on the formation and emergence of massive clusters

2015 ◽  
Vol 12 (S316) ◽  
pp. 177-183
Author(s):  
James E. Dale
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Massive Stars ◽  
Cluster Structure ◽  
Star Clusters ◽  
Stellar Feedback ◽  
Making Sense ◽  
Formation Efficiency ◽  
Massive Clusters ◽  
Made In

AbstractMassive star clusters are of fundamental importance both observationally, since they are visible at such great distances, and theoretically, because of their influence on the large–scale ISM. Understanding stellar feedback is a prerequisite for making sense of their formation and early evolution, since feedback influences cluster structure, star formation efficiency, and sets the timescales on which clusters emerge from their parent clouds to become optically visible. I review the progress made in understanding these issues from a numerical perspective.

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 Star Clusters and Galactic Chemodynamics: Implosive Formation of Super Star Clusters

2004 ◽  
Vol 21 (2) ◽  
pp. 167-170 ◽  
Author(s):  
Kenji Bekki
Keyword(s):  
Globular Clusters ◽  
Large Scale ◽  
Chemical Properties ◽  
Star Clusters ◽  
Small Scale ◽  
Merging Galaxies ◽  
Central Regions ◽  
Strong Compression ◽  
Super Star Clusters ◽  
Tidal Tails

AbstractWe numerically investigate dynamical and chemical properties of star clusters (open and globular clusters, and ‘super star clusters’, SSC) formed in interacting/merging galaxies. The investigation is two-fold: (a) large-scale (100 pc–100 kpc) SPH simulations on density and temperature evolution of gas in interacting/merging galaxies and (b) small-scale simulations on the effects of the high gas pressure of the ISM on the evolution of molecular clouds. We find that the pressure of ISM in merging galaxies can become higher than the internal pressure of GMCs (∼105kB K cm–3), in particular, in the tidal tails or the central regions of mergers. We also find that GMCs can collapse to form SSCs within an order of 107 yr due to the strong compression by the high-pressure ISM in mergers.

scholarly journals Signatures of the Youngest Starbursts: The Discovery of Ultradense HII Regions

2002 ◽  
Vol 12 ◽  
pp. 175-176
Author(s):  
Kelsey E. Johnson
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Star Clusters ◽  
Hii Regions ◽  
Starburst Galaxies ◽  
Local Universe ◽  
The Galaxy ◽  
Super Star Clusters ◽  
Ultracompact Hii

Globular clusters are ubiquitous in the local universe, and their younger and bluer siblings, “super star clusters” (SSCs), have been observed in a large number of starburst galaxies. Recently a handful of ultra-young SSCs have been foundstill embedded in their birth material(e.g. Kobulnicky &amp; Johnson 1999 (here after KJ99); Turner et al. 2000; Beck et al. 2000; Tarchi et al. 2000). Because of their similarity (although on a vastly larger scale) to ultracompact HII regions in the Galaxy, KJ99 dub these embedded massive star clusters “ultradense HII regions” (UDHIIs). I will review the discovery of UDHIIs, their modeled properties, and their connection to the more familiar Galactic ultracompact HII regions.

scholarly journals Pre-Collapse Evolution of Galactic Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 365-366
Author(s):  
Toshiyuki Fukushige ◽  
Douglas C. Heggie
Keyword(s):  
Mass Spectrum ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Globular Clusters ◽  
Star Clusters ◽  
Early Evolution ◽  
Initial Structure ◽  
Spherically Symmetric ◽  
Order Of Magnitude ◽  
Model Star

We investigated collisionless aspects of the early evolution of model star clusters. The effects of mass loss through stellar evolution and of a steady tidal field are modelled using N-body simulations. Our results (which depend on the assumed initial structure and the mass spectrum) agree qualitatively with those of Chernoff & Weinberg (1990), who used a Fokker-Planck model with a spherically symmetric tidal cutoff. For those systems which are disrupted, the lifetime to disruption generally exceeds that found by Chernoff & Weinberg, sometimes by as much as an order of magnitude.

scholarly journals The dynamical effect of white dwarf kicks in star clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 318-319
Author(s):  
Harvey B. Richer
Keyword(s):  
Globular Clusters ◽  
Star Clusters ◽  
Core Collapse ◽  
Dynamical Models ◽  
Intermediate Mass ◽  
Heating Source ◽  
The Core ◽  
Central Heating ◽  
Massive Clusters ◽  
Hubble Time

AbstractGlobular star clusters generally have large cores, i.e., rc/rh (the ratio of core to half-light radii) exceeds 0.3 for more than 50% of the Galactic globular clusters. In the absence of a central heating source, dynamical models suggest that massive clusters will contract, typically on a timescale shorter than a Hubble time, and exhibit a compact core. To explain the disagreement between observations and theory, intermediate-mass mass black holes have been invoked to explain the core structure. Recent observations, however, have failed to definitively prove their existence in clusters. A new scenario, involving a natal kick given to white dwarfs may provide the required heating and help clusters avoid or delay core collapse.

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