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 Discovery of Infrared Stars in Globular Clusters in the Magellanic Clouds and Their Light Variations

1998 ◽  
Vol 11 (1) ◽  
pp. 395-395
Author(s):  
S. Nishida ◽  
T. Tanabé ◽  
S. Matsumoto ◽  
T. Onaka ◽  
Y. Nakada ◽  
...  
Keyword(s):  
Mass Loss ◽  
Globular Clusters ◽  
Main Sequence ◽  
Near Infrared ◽  
Magellanic Clouds ◽  
Infrared Light ◽  
Agb Stars ◽  
Dust Shells ◽  
Infrared Stars ◽  
Infrared Survey

A systematic near-infrared survey was made for globular clusters in the Magellanic Clouds. Two infrared stars were discovered in NGC419 (SMC) and NGC1783 (LMC). NGC419 and NGC1783 are well-studied rich globular clusters whose turn-off masses and ages are estimated MTO ~ 2.0 Mʘ and т ~1.2 Gyr for NGC419, and MT0 ~ 2.0 Mʘ and т ʘ 0.9 Gyr for NGC1783, respectively. The periods of the infrared light variations were determined to be 540 dfor NGC419IR1 and to be 480 d for NGC1783IR1, respectively. Comparison of the measurements with the period—if magnitude relation for carbon Miras in the LMC by Groenewegen and Whitelock(1996) revealed that the Kmagnitudes of the infrared stars were fainter by about 0.3 — 0.8 magnitude than those predicted by the P — K relation. This deviation can be explained if the infrared stars are surrounded by thick dust shells and are obscured even in the K band. The positions of NGC419IR1and NGC1783IR1 on the P — K diagram suggest that AGB stars with the main sequence masses of about 2 Mʘ start their heavy mass-loss when P ʘ 500 d.

scholarly journals Non-LTE Analysis of Massive Stars in the Magellanic Clouds

1986 ◽  
Vol 116 ◽  
pp. 413-414
Author(s):  
T. Gehren ◽  
D. Husfeld ◽  
R.P. Kudritzki ◽  
P.S. Conti ◽  
D.G. Hummer
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Emission Spectra ◽  
Mass Function ◽  
Magellanic Clouds ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Echelle Spectrograph ◽  
Chemical Abundances ◽  
First Results

The massive stars of the Magellanic Clouds are of considerable current interest with regard to questions of initial mass function, star formation mechanisms, stellar evolution with mass loss and the chemical evolution of galaxies. The effective temperatures, surface gravities and helium abundances of 6 main sequence O-type stars, obtained by fitting non-LTE model atmospheres to high quality spectra, are presented here; these are the first results from a long-term program to determine accurately the parameters and chemical abundances of massive stars in the Magellanic Clouds. The program stars were selected to be main sequence objects, according to the classification of Conti et al. (1985, in prep.), with He II λ 4686 Å in absorption, and to have minimal reddening and nebular emission. Spectra were obtained in 1984 December with the Cassegrain echelle spectrograph (CASPEC) and a CCD detector at the ESO 3.6 m telescope. A preliminary analysis of these spectra has been carried out by fitting the equivalent widths of He I λ 4471 Å and the profiles of Hγ and the Pickering lines (for details of the technique, see Kudritzki, 1980). The resulting values of effective temperature and gravity are given in Table I, along with the identification, spectral type and mv, of each star.

scholarly journals What Young Massive Clusters in the Magellanic Clouds teach us about Old Galactic Globular Clusters?

2018 ◽  
Vol 14 (S343) ◽  
pp. 314-317
Author(s):  
Francesca D’Antona ◽  
Paolo Ventura ◽  
Aaron Dotter ◽  
Sylvia Ekström ◽  
Marco Tailo
Keyword(s):  
Globular Clusters ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Differential Analysis ◽  
Slowing Down ◽  
Magnitude Diagram ◽  
First Results ◽  
Rotational Evolution ◽  
Galactic Globular Clusters ◽  
Massive Clusters

Abstract. The Asymptotic Giant Branch (AGB) scenario ascribes the multiple populations in old Galactic Globular Clusters (GGC) to episodes of star formation in the gas contaminated by the ejecta of massive AGBs and super-AGBs of a first stellar population. The mass of these AGBs (4-8 M⊙) today populate the Young Massive Clusters (YMC) of the Magellanic Clouds, where rapid rotation and its slowing down play an important role in shaping the color-magnitude diagram features. Consequently, we must reconsider whether the rotational evolution of these masses affects the yields, and whether the resulting abundances are compatible with the chemical patterns observed in GGC. We show the first results of a differential analysis, by computing the hot bottom burning evolution of non-rotating models with increased CNO-Na abundances at the second dredge-up, following the results of MESA rotational models.

scholarly journals Observational signatures of lithium depletion in the metal-poor globular cluster NGC6397

2009 ◽  
Vol 5 (S268) ◽  
pp. 263-268 ◽  
Author(s):  
Karin Lind ◽  
Francesca Primas ◽  
Corinne Charbonnel ◽  
Frank Grundahl ◽  
Martin Asplund
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Main Sequence Stars ◽  
Surface Evolution ◽  
Halo Stars ◽  
Systematic Uncertainties ◽  
Low Mass ◽  
Lithium Depletion

AbstractThe “stellar” solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular clusters are ideal environments for studies of the surface evolution of lithium, with large number statistics possible to obtain for main sequence stars as well as giants. We discuss the Li abundances measured for >450 stars in the globular cluster NGC 6397, focusing on the evidence for lithium depletion and especially highlighting how the inferred abundances and interpretations are affected by early cluster self-enrichment and systematic uncertainties in the effective temperature determination.

scholarly journals Correlations between the age structure in early-type galaxies and their properties

2007 ◽  
Vol 3 (S245) ◽  
pp. 305-306
Author(s):  
Maren Hempel
Keyword(s):  
Age Structure ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Near Infrared ◽  
Age Distribution ◽  
Age Difference ◽  
Early Type ◽  
Groups Of Galaxies ◽  
First Results ◽  
Galaxy Environment

AbstractWe present the results on our investigation of the age structure in early-type galaxies, based on optical/near-infrared photometry. First results have shown that the age structure in early-type galaxies is not as uniform as previously thought. The conclusion can only be that the formation of these galaxies is not exclussively based on a single scenario, e.g. monolithic collapse, or hierarchical merging. In our galaxy survey we compare the age structure of galaxies in different galaxy environment, of different mass and with different integral light properties, using the globular cluster systems as stellar probes. Depending on the size of the globular cluster sample we derive a cumulative age distribution and compare it to simulated systems with a known age structure. This allows us to detect globular cluster sub-populations with an age difference of several Gyr. So far we have found two galaxies, members of small groups of galaxies, which contain a significant population of intermediate age globular clusters in the inner region of the galaxy.

scholarly journals A Search for Tidal Stellar Debris from the Magellanic Clouds: Survey Results from the First Two Years

1999 ◽  
Vol 190 ◽  
pp. 508-510 ◽  
Author(s):  
S. R. Majewski ◽  
J. C. Ostheimer ◽  
W. E. Kunkel ◽  
K. V. Johnston ◽  
R. J. Patterson ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Halo ◽  
Large Magellanic Cloud ◽  
Main Sequence Stars ◽  
Tidal Disruption ◽  
Negative Results ◽  
Ram Pressure ◽  
Survey Results ◽  
Magellanic Stream

An important discriminant between leading models for the origin of the Magellanic Stream is the presence of a stellar counterpart to the HI gas stream: ram pressure stripping of gas by a putative hot Galactic halo would act only on Magellanic gas while gravitational tidal stripping would act on both gas and stars. Several previous attempts to find tidal stellar debris have failed to find carbon stars, A stars, or other main sequence stars in the Magellanic Stream (Mathewson et al. 1979; Recillas-Cruz 1982; Brück & Hawkins 1983; Guhathakurta & Lin 1999). However, there has long been a suggestion (Kunkel 1979; Lynden-Bell 1982) of a possible Magellanic association of satellite galaxies and globular clusters that have similar orbits and may derive from the break up of a greater Magellanic galaxy (Lynden-Bell & Lynden-Bell 1995; Majewski et al. 1997). Recent models (Moore & Davis 1994; Johnston 1998) of the tidal disruption of Large Magellanic Cloud (LMC)-like systems indicate a wide dispersal of debris, much wider than the rather confined HI stream, so that the contrast of tidal debris against the Galactic fore/background would be low. If true, this could explain some of the previous negative results for tidal debris searches.

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 Old and intermediate populations in the Magellanic Clouds

1964 ◽  
Vol 20 ◽  
pp. 349-354 ◽  
Author(s):  
W. G. Tifft
Keyword(s):  
Globular Clusters ◽  
Galactic Halo ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Similar Type ◽  
Galactic Population ◽  
Galactic Clusters ◽  
The Galaxy ◽  
The Common ◽  
Common Field

It is becoming increasingly evident that the older stellar components of the Magellanic Clouds are significantly younger, on the average, than the old star component of the Galaxy. Magellanic Cloud red globular-like clusters of the NGC 419 variety, and the common field stars of similar type, are almost certainly to be classified as intermediate-age populations by galactic standards. The oldest galactic population, seen in the galactic halo, globular clusters, and oldest galactic clusters, is apparently very sparse in the Magellanic Clouds, although in the SMC at least something very similar is seen in and near NGC 121.

scholarly journals Multiple stellar populations in massive LMC star clusters

2008 ◽  
Vol 4 (S256) ◽  
pp. 305-310
Author(s):  
A. D. Mackey ◽  
P. Broby Nielsen ◽  
A. M. N. Ferguson ◽  
J. C. Richardson
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Cluster Formation ◽  
Star Clusters ◽  
Stellar Populations ◽  
Star Cluster ◽  
Magellanic Clouds ◽  
Formation And Evolution ◽  
Galactic Globular Clusters

AbstractThe recent discovery of multiple stellar populations in massive Galactic globular clusters poses a serious challenge for models of star cluster formation and evolution. A new angle on this problem is being provided by rich intermediate-age clusters in the Magellanic Clouds. In this contribution we describe the discovery of three such LMC clusters with peculiar main-sequence turn-off morphologies. The simplest interpretation of our observations is that each of these three clusters is comprised of two or more stellar populations spanning an age interval of ~300 Myr. Surprisingly, such features may not be unusual in this type of cluster.

scholarly journals Pre-main-sequence Stars in the SMC and LMC

1999 ◽  
Vol 190 ◽  
pp. 366-367 ◽  
Author(s):  
Wolfgang Brandner ◽  
Eva K. Grebel ◽  
Hans Zinnecker ◽  
Bernhard Brandl
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
High Mass ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
First Results ◽  
Low Mass

We present first results of a survey for pre-main-sequence stars in the Magellanic Clouds. Our search concentrated on NGC 346, the most prominent OB association in the Small Magellanic Cloud, and on the 30 Dor starburst cluster in the Large Magellanic Cloud. The identification of the young low- to intermediate-mass stellar population in the SMC and LMC allows us to study whether or not these populations formed simultaneously with high-mass stars, and to what an extent lower metallicity affects the low-mass IMF. We can also evaluate the duration of star formation in a starburst region.

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