scholarly journals The Older Clusters in the Magellanic Clouds

1980 ◽  
Vol 85 ◽  
pp. 305-315 ◽  
Author(s):  
S.C.B. Gascoigne
Keyword(s):  
Globular Clusters ◽  
Magellanic Clouds ◽  
Parameter Family ◽  
List Type ◽  
Type Number ◽  
Cloud Clusters ◽  
The Galaxy ◽  
Long Time ◽  
The Subject ◽  
Two Parameter

We begin with Fig. 1, which somewhat aged though it may be still illustrates important aspects of the subject (Gascoigne 1971) (i)There is a clear division of cloud clusters into a blue and red group. The division corresponds to the mass around 2.51M⊙, at which core degeneracy first develops in stars approaching the giant branch. Such stars spend about three times as long on the giant branch and travel higher up it than the slightly heavier non-degenerate stars, and so dominate the colours of the clusters in which they occur.(ii)The red clusters are somewhat less luminous than the globular clusters in the galaxy. Freeman and Chun (1972) have shown from dynamic arguments that the cloud clusters are also less massive, by enough to keep the M/L ratios roughly the same as those in the galaxy.(iii)For a long time it has been taken that the blue clusters are young and the red clusters old. Thus the clouds present us with a truly two-parameter family of globular-like clusters, the parameters being of course age and abundance.

scholarly journals Theoretical considerations of the warp and thickening

1979 ◽  
Vol 84 ◽  
pp. 513-522 ◽  
Author(s):  
E. Saar
Keyword(s):  
Galactic Disk ◽  
Magellanic Clouds ◽  
List Type ◽  
Type Number ◽  
Tidal Influence ◽  
The Galaxy ◽  
The Subject ◽  
Theoretical Considerations

As a theoretical subject, the study of the bending of the gaseous planes of galaxies has not been extremely popular. It seems that this is due to an excellent and thorough paper on the subject, published by Hunter and Toomre in 1969. At that time there existed three (or four) rival theoretical mechanisms: (1)vertical oscillations of the galactic disk, considered first by Lynden-Bell (1965);(2)asymmetrical pressure on the disk due to intergalactic wind (Kahn and Woltjer 1959);(3)tidal influence of the Magellanic Clouds, from (a)the case of Stationary Clouds, and(b)the case of Clouds orbiting around the Galaxy (Elwert and Hablick 1965, Avner and King 1967).

scholarly journals Summary of a contribution on “the Magellanic Clouds”

1959 ◽  
Vol 10 ◽  
pp. 51-51
Author(s):  
M. W. Feast ◽  
A. D. Thackeray ◽  
A. J. Wesselink
Keyword(s):  
Magellanic Clouds ◽  
List Type ◽  
Type Number ◽  
The Galaxy

Combined spectroscopic and photo-electric observations of bright stars in the two Magellanic Clouds show that: 1)There is no marked difference between the stars observed in the two Clouds when compared with each other or with normal galactic supergiants, as judged by: (a)direct spectroscopic comparison,(b)Hertzsprung-Russell diagram,(c)U, B, V plot.2)Stars observed in both Clouds suffer a small amount of absorption, the precise amount depending on the intrinsic colours adopted. How much of the absorption takes place within the Clouds remains to be determined.3)A reddening path has been determined by comparison of Cloud stars (little reddened) and galactic supergiants (heavily reddened). The observations are consistent with a single reddening path and have not yet suggested any difference in the absorbing properties of dust in the Clouds and in the Galaxy. A conclusion on this latter point must await observations of heavily reddened stars in the Clouds.

Comparison of the galactic system with other stellar systems

1958 ◽  
Vol 5 ◽  
pp. 69-73 ◽  
Author(s):  
J. H. Oort
Keyword(s):  
Globular Clusters ◽  
The Other ◽  
General Distribution ◽  
Stellar Systems ◽  
List Type ◽  
Type Number ◽  
Galactic System ◽  
The Galaxy ◽  
Andromeda Nebula ◽  
Made In

A comparison of the Galactic System with other stellar systems might be based on: (a)the regular aspect (the population 11);(b)what we might call the semi-chaotic aspect, presented by the gas and the other population 1 objects;(c)the spherical corona of continuous radio-emission.As far as (a) is concerned we are not yet in a position to say very much. The only type of objects of extreme population 11 that we have recognized with certainty in the Galactic System as well as in other comparable systems are the globular clusters. They are very incompletely known in the Galaxy, perhaps somewhat more completely in the Andromeda nebula, but few systematic studies have been made in other systems. So far as we can tell, the Andromeda nebula and the Galactic System are comparable in the number and general distribution of globular clusters.

scholarly journals How to Model the Chemical Evolution of Galaxies

1993 ◽  
Vol 155 ◽  
pp. 557-566
Author(s):  
Joachim Köppen
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Time Scale ◽  
Life Time ◽  
Magellanic Clouds ◽  
Formation Time ◽  
List Type ◽  
The Galaxy ◽  
H Ii Region ◽  
Magellanic Stream

For a first interpretation of the comparison of observational data, the crude “Simple Model” of chemical evolution is quite useful. Since it has well been described in the literature (e.g. Pagel and Patchett 1975, Tinsley 1980), let us here just review the assumptions and whether they are satisfied: 1.The galaxy is a closed system, with no exchange of matter with its surroundings: For the solar neighbourhood this probably is not true (the infamous Gdwarf-“problem”, Pagel 1989b). For the Magellanic Clouds this is most certainly wrong, because of the presence of the Inter-Cloud Region and the Magellanic Stream, and evidence for interaction with each other and the Galaxy as well (cf. e.g. Westerlund 1990).2.It initially consists entirely of gas (without loss of generality of primordial composition): This is good approximation also for models with gas infall, as long as the infall occurs with a time scale shorter than the star formation time scale.3.The metal production of the average stellar generation (the yield y) is constant with time: Initially, it is reasonable to make this assumption. For tables of the oxygen yield see Koppen and Arimoto (1991).4.The metal rich gas ejected by the stars is completely mixed with the ambient gas. To neglect the finite stellar life times (“instantaneous recycling approximation”) is appropriate for elements synthesized in stars whose life time is much shorter than the star formation time scale, such as oxygen, neon, sulphur, and argon.5.The gas is well mixed at all times: We don't know. The dispersion of H II region abundances may give an indication. In the Magellanic Clouds Dufour (1984) finds quite a low value (±0.08 dex for oyxgen).

scholarly journals Star clusters in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 161-164 ◽  
Author(s):  
S. van den Bergh
Keyword(s):  
Cluster Formation ◽  
Star Clusters ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Small Magellanic Cloud ◽  
Cloud Clusters ◽  
The Galaxy

Star clusters in the Magellanic Clouds (MCs) differ from those in the Galaxy in a number of respects: (1) the Clouds contain a class of populous open clusters that has no Galactic counterpart; (2) Cloud clusters have systematically larger radii rh than those in the Galaxy; (3) clusters of all ages in the Clouds are, on average, more flattened than those in the Galaxy. In the Large Magellanic Cloud (LMC) there appear to have been two distinct epochs of cluster formation. LMC globulars have ages of 12-15 Gyr, whereas most populous open clusters have ages <5 Gyr. No such dichotomy is observed for clusters in the Small Magellanic Cloud (SMC) The fact that the SMC exhibits no enhanced cluster formation at times of bursts of cluster formation in the LMC, militates against encounters between the Clouds as a cause for enhanced rates of star and cluster formation.

scholarly journals The red globular-like clusters in the Magellanic Clouds

1964 ◽  
Vol 20 ◽  
pp. 354-357
Author(s):  
S. C. B. Gascoigne
Keyword(s):  
Chemical Composition ◽  
Globular Cluster ◽  
Spherical Symmetry ◽  
Globular Clusters ◽  
Progress Report ◽  
Magellanic Clouds ◽  
Systematic Observation ◽  
The Galaxy

There are about 50 clusters in the Magellanic Clouds which from their spherical symmetry, integrated colours, and luminosities appear similar to the globular clusters in the Galaxy. The colour-magnitude diagrams of these clusters should give moduli for the Clouds, indications of the age and chemical composition of the clusters themselves, and perhaps some information about the evolutionary tracks of old stars generally. The first investigation of this kind was carried out by Arp on the SMC clusters NGC 361 and 419. This was followed by papers by Eggen and Sandage and by the writer on NGC 1783 in the LMC, and by Tifft (1962) on NGC 121 in the SMC. Of these four clusters only NGC 121 appeared really similar to a galactic globular cluster, the others displaying features not reproduced by any known cluster in the Galaxy. Further work was clearly needed to clarify the problems raised by these results, and a program for the systematic observation of the colour-magnitude diagrams of red clusters in the Clouds was accordingly begun here in September 1961. This contribution is a progress report on this program.

scholarly journals Short Period Variables in the Magellanic Cloud Cluster NGC 1466

1973 ◽  
Vol 21 ◽  
pp. 113-119 ◽  
Author(s):  
M. V. Norris
Keyword(s):  
Globular Cluster ◽  
Metal Content ◽  
Globular Clusters ◽  
Magellanic Clouds ◽  
Horizontal Branch ◽  
A Value ◽  
Short Period ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Metal Abundance

NGC 1466 (α1950 = 3h44.m6, δ1950= -71°45’) is a globular cluster which appears to be situated between the two Magellanic Clouds. Previous estimates (Gascoigne, 1966) put it at roughly the same distance from us as the LMC, so it is regarded as a member of the Cloud system. It is globular in appearance, and its colour-magnitude diagram confirms this classification. It has a fairly well-developed horizontal branch, and was found by Wesselink (1970) to be quite rich in variables. The metallicity index, Q, (van den Bergh, 1967) has a value of -0.36 for NGC 1466 (Andrews and Lloyd Evans, 1971). This would rank it with M5 and NGC 6171 as a cluster of intermediate metal content. This comparison is consistent with the value of Δ V for the cluster, which, at 2.m6, is representative of the Δ V values of globular clusters of intermediate metal abundance in the Galaxy.

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