scholarly journals Star Clusters in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 397-404 ◽  
Author(s):  
G. S. Da Costa
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Field Star ◽  
Age Gap ◽  
Significant Change ◽  
New Evidence ◽  
Cluster Age

Recent results for the old and intermediate-age star clusters of the Magellanic Clouds are reviewed. Highlights include new evidence that the LMC old clusters are as old the Galaxy's halo globular clusters and the persistence of the LMC cluster “Age Gap” despite field star evidence for significant star formation during the cluster age gap epoch. For the SMC new data confirm the lack of significant change in cluster abundances with age prior to ~4 Gyr ago.

scholarly journals X-ray sources in Galactic globular clusters and old open clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 367-376
Author(s):  
Maureen van den Berg
Keyword(s):  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Star Clusters ◽  
Open Clusters ◽  
Encounter Rate ◽  
X Ray ◽  
Low Mass ◽  
New Perspective ◽  
X Ray Binaries ◽  
Cluster Age

AbstractThe features and make up of the population of X-ray sources in Galactic star clusters reflect the properties of the underlying stellar environment. Cluster age, mass, stellar encounter rate, binary frequency, metallicity, and maybe other properties as well, determine to what extent we can expect a contribution to the cluster X-ray emission from low-mass X-ray binaries, millisecond pulsars, cataclysmic variables, and magnetically active binaries. Sensitive X-ray observations withXMM-Newton and certainlyChandra have yielded new insights into the nature of individual sources and the effects of dynamical encounters. They have also provided a new perspective on the collective X-ray properties of clusters, in which the X-ray emissivities of globular clusters and old open clusters can be compared to each other and to those of other environments. I will review our current understanding of cluster X-ray sources, focusing on star clusters older than about 1 Gyr, illustrated with recent results.

scholarly journals Light element variations within the different age-metallicity populations in the nucleus of the Sagittarius dwarf

2019 ◽  
Vol 490 (1) ◽  
pp. L67-L70 ◽  
Author(s):  
Alison Sills ◽  
Emanuele Dalessandro ◽  
Mario Cadelano ◽  
Mayte Alfaro-Cuello ◽  
J M Diederik Kruijssen
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Star Clusters ◽  
Light Element ◽  
Iron Complex ◽  
Star Cluster ◽  
Chromosome Maps ◽  
Insight Into ◽  
Poor Population

ABSTRACT The cluster M54 lies at the centre of the Sagittarius dwarf spheroidal galaxy, and therefore may be the closest example of a nuclear star cluster. Either in situ star formation, inspiralling globular clusters, or a combination have been invoked to explain the wide variety of stellar sub-populations in nuclear star clusters. Globular clusters are known to exhibit light element variations, which can be identified using the photometric construct called a chromosome map. In this letter, we create chromosome maps for three distinct age-metallicity sub-populations in the vicinity of M54. We find that the old, metal-poor population shows the signature of light element variations, while the young and intermediate-age metal rich populations do not. We conclude that the nucleus of Sagittarius formed through a combination of in situ star formation and globular cluster accretion. This letter demonstrates that properly constructed chromosome maps of iron-complex globular clusters can provide insight into the formation locations of the different stellar populations.

scholarly journals The search for multiple populations in Magellanic Clouds clusters – V. Correlation between cluster age and abundance spreads

2019 ◽  
Vol 487 (4) ◽  
pp. 5324-5334 ◽  
Author(s):  
S Martocchia ◽  
E Dalessandro ◽  
C Lardo ◽  
I Cabrera-Ziri ◽  
N Bastian ◽  
...  
Keyword(s):  
Significant Role ◽  
Massive Star ◽  
Milky Way ◽  
Star Clusters ◽  
Magellanic Clouds ◽  
Key Factors ◽  
Strong Function ◽  
Combining Data ◽  
Chemical Anomalies ◽  
Cluster Age

ABSTRACT In our HST photometric survey, we have been searching for multiple stellar populations (MPs) in Magellanic Clouds (MCs) massive star clusters which span a significant range of ages (∼1.5–11 Gyr). In the previous papers of the series, we have shown that the age of the cluster represents one of the key factors in shaping the origin of the chemical anomalies. Here, we present the analysis of four additional clusters in the MCs, namely Lindsay 38, Lindsay 113, NGC 2121, and NGC 2155, for which we recently obtained new UV HST observations. These clusters are more massive than ∼104 M⊙ and have ages between ∼2.5 and ∼6 Gyr, i.e. located in a previously unexplored region of the cluster age/mass diagram. We found chemical anomalies, in the form of N spreads, in three out of four clusters in the sample, namely in NGC 2121, NGC 2155, and Lindsay 113. By combining data from our survey and HST photometry for three additional clusters in the Milky Way (namely 47 Tuc, M15, and NGC 2419), we show that the extent of the MPs in the form of N spread is a strong function of age, with older clusters having larger N spreads with respect to the younger ones. Hence, we confirm that cluster age plays a significant role in the onset of MPs.

scholarly journals Modeling Formation of Globular Clusters: Beacons of Galactic Star Formation

2010 ◽  
Vol 6 (S270) ◽  
pp. 381-384
Author(s):  
Oleg Y. Gnedin
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Star Clusters ◽  
Mass Function ◽  
Giant Molecular Clouds ◽  
Early Galaxies ◽  
The Masses

AbstractModern hydrodynamic simulations of galaxy formation are able to predict accurately the rates and locations of the assembly of giant molecular clouds in early galaxies. These clouds could host star clusters with the masses and sizes of real globular clusters. I describe current state-of-the-art simulations aimed at understanding the origin of the cluster mass function and metallicity distribution. Metallicity bimodality of globular cluster systems appears to be a natural outcome of hierarchical formation and gradually declining fraction of cold gas in galaxies. Globular cluster formation was most prominent at redshifts z > 3, when massive star clusters may have contributed as much as 20% of all galactic star formation.

scholarly journals Results from HST Observations of Six LMC Globular Cluster Fields

1999 ◽  
Vol 190 ◽  
pp. 448-449 ◽  
Author(s):  
K. A. G. Olsen ◽  
P. W. Hodge ◽  
M. Mateo ◽  
E. W. Olszewski ◽  
R. A. Schommer ◽  
...  
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Milky Way ◽  
Evolutionary Models ◽  
First Stars ◽  
Field Star ◽  
Star Studies ◽  
Red Giant ◽  
Star Formation Histories ◽  
Best Fit

We present deep HST color-magnitude diagrams of fields centered on the six old LMC globular clusters NGC 1754, NGC 1835, NGC 1898, NGC 1916, NGC 2005, and NGC 2019. Separate cluster and field star CMDs are shown. The time of formation of the LMC is studied from an analysis of the cluster CMDs. Based on a comparison of the CMDs with sequences of the Milky Way clusters M3, M5, and M55, we suggest that the LMC formed its first stars at the same time as the Milky Way to within 1 Gyr. We find additional evidence that these LMC globular clusters are as old as the oldest Milky Way clusters through a comparison of our data with the horizontal branch evolutionary models of Lee, Demarque, & Zinn (1994).The evolution of the LMC following its formation is studied through an analysis of the field star CMDs. Through an automated comparison with stellar evolution models, we extract the star formation histories implied by the CMDs. Our best-fit star formation histories imply that the LMC has been actively forming stars over the last 4 Gyr, in agreement with previous field star studies. The four fields that lie in the Bar also contain significant numbers of stars with ages of 4–8 Gyr in the best-fit cases. The most notable disagreement between the best-fit models and observed CMDs is in the color of the red giant branch.

scholarly journals The age-abundance relations and age distributions for the star clusters of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 183-189 ◽  
Author(s):  
G. S. Da Costa
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Large Population ◽  
Age Distribution ◽  
Magellanic Clouds ◽  
Number Of Clusters ◽  
First Results ◽  
Single Cluster ◽  
Cluster Age

A sample of Large Magellanic Clouds (LMC) and Small Magellanic Clouds (SMC) clusters for which ages have been directly determined from main sequence turnoff photometry has been compiled. According to this sample, the LMC and SMC cluster age distributions are very different. The LMC contains a large population of 1 to 3 Gyr old clusters as well as a small number of clusters that appear to be as old as the Galactic halo globular clusters. Surprisingly however, only a single cluster is known with an age in the interval between 3 Gyr and the age, taken as 15 Gyr, of the oldest clusters. The SMC age distribution, on the other hand, is much broader. It extends back to approximately 12 Gyr but there appear to be no SMC clusters as old as the oldest in the LMC. The sample of clusters is also used to discuss the age-abundance relations for both galaxies. Little can be learned for the LMC but it appears that the chemical evolution of the SMC differed in form from that experienced in the solar neighbourhood. The first results of an imaging survey designed to find LMC clusters with ages exceeding 3 Gyr are also described.

scholarly journals From nuclear clusters to halo globulars: Star clusters as basic galactic building blocks

2006 ◽  
Vol 2 (S235) ◽  
pp. 48-51
Author(s):  
Richard de Grijs
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Building Blocks ◽  
Dominant Mode ◽  
Star Formation History ◽  
Formation Mode ◽  
Formation History ◽  
Nuclear Clusters

AbstractI assess the similarities and differences between the star-formation modes in quiescent spiral galaxies versus those in violent starburst regions, including galactic nuclei. As opposed to the quiescent star-formation mode, current empirical evidence on the star-formation processes in the extreme, high-pressure environments induced by galaxy encounters strongly suggests that star cluster formation is an important and perhaps even the dominant mode of star formation in such starburst events. This implies that by using star clusters as unique diagnostic probes, we can trace a galaxy's most violent star formation history very well, at least for the past few Gyr. The sizes, luminosities, and mass estimates of the young massive star clusters are entirely consistent with what is expected for young Milky Way-type globular clusters (GCs). Recent evidence lends support to the scenario that GCs, which were once thought to be the oldest building blocks of galaxies, are still forming today.

scholarly journals Ages and Metallicities of Five Intermediate-Age Star Clusters Projected Towards the Small Magellanic Cloud

2002 ◽  
Vol 207 ◽  
pp. 196-198
Author(s):  
Juan J. Clariá ◽  
Andrés E. Piatti ◽  
João F. C. Santos ◽  
Eduardo Bica ◽  
Ata Sarajedini ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Central Body ◽  
Age Distribution ◽  
Star Clusters ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Ccd Photometry ◽  
Cluster Age

Washington CCD photometry of intermediate-age clusters in the Small Magellanic Cloud (SMC) is presented. The cluster age distribution in the SMC suggests formation epochs at 3 and 6 Gyr, respectively. Recent star formation is confined to the central body of the SMC. The chemical evolution of the SMC appears to be best represented by bursty models.

scholarly journals Simulating star clusters across cosmic time – II. Escape fraction of ionizing photons from molecular clouds

2020 ◽  
Vol 492 (4) ◽  
pp. 4858-4873 ◽  
Author(s):  
Chong-Chong He ◽  
Massimo Ricotti ◽  
Sam Geen
Keyword(s):  
Star Formation ◽  
Ionizing Radiation ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Compact Star ◽  
Star Clusters ◽  
Cosmic Time ◽  
Star Cluster ◽  
Star Forming ◽  
Radiation Feedback

ABSTRACT We calculate the hydrogen- and helium-ionizing radiation escaping star-forming molecular clouds, as a function of the star cluster mass and compactness, using a set of high-resolution radiation-magnetohydrodynamic simulations of star formation in self-gravitating, turbulent molecular clouds. In these simulations, presented in He et al., the formation of individual massive stars is well resolved, and their UV radiation feedback and lifetime on the main sequence are modelled self-consistently. We find that the escape fraction of ionizing radiation from molecular clouds, $\langle f_{\rm esc}^{\scriptscriptstyle \rm MC}\rangle$ , decreases with increasing mass of the star cluster and with decreasing compactness. Molecular clouds with densities typically found in the local Universe have negligible $\langle f_{\rm esc}^{\scriptscriptstyle \rm MC}\rangle$ , ranging between $0.5{{\ \rm per\ cent}}$ and $5{{\ \rm per\ cent}}$. 10 times denser molecular clouds have $\langle f_{\rm esc}^{\scriptscriptstyle \rm MC}\rangle$ $\approx 10{{\ \rm per\ cent}}{-}20{{\ \rm per\ cent}}$, while 100× denser clouds, which produce globular cluster progenitors, have $\langle f_{\rm esc}^{\scriptscriptstyle \rm MC}\rangle$ $\approx 20{{\ \rm per\ cent}}{-}60{{\ \rm per\ cent}}$. We find that $\langle f_{\rm esc}^{\scriptscriptstyle \rm MC}\rangle$ increases with decreasing gas metallicity, even when ignoring dust extinction, due to stronger radiation feedback. However, the total number of escaping ionizing photons decreases with decreasing metallicity because the star formation efficiency is reduced. We conclude that the sources of reionization at z > 6 must have been very compact star clusters forming in molecular clouds about 100× denser than in today’s Universe, which lead to a significant production of old globular clusters progenitors.

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.

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