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|A Revised and Extended Catalog of Magellanic System Clusters, Associations, and Emission Nebulae. II. The Large Magellanic Cloud|
A survey of extended objects in the Large Magellanic Cloud was carriedout on the ESO/SERC R and J Sky Survey Atlases, checking entries inprevious catalogs and searching for new objects. The census provided6659 objects including star clusters, emission-free associations, andobjects related to emission nebulae. Each of these classes containsthree subclasses with intermediate properties, which are used to infertotal populations. The survey includes cross identifications amongcatalogs, and we present 3246 new objects. We provide accuratepositions, classification, and homogeneous measurements of sizes andposition angles, as well as information on cluster pairs andhierarchical relation for superimposed objects. This unification andenlargement of catalogs is important for future searches of fainter andsmaller new objects. We discuss the angular and size distributions ofthe objects of the different classes. The angular distributions show twooff-centered systems with different inclinations, suggesting that theLMC disk is warped. The present catalog together with its previouscounterpart for the SMC and the inter-Cloud region provide a totalpopulation of 7847 extended objects in the Magellanic System. Theangular distribution of the ensemble reveals important clues on theinteraction between the LMC and SMC.
|Integrated UBV Photometry of 624 Star Clusters and Associations in the Large Magellanic Cloud|
We present a catalog of integrated UBV photometry of 504 star clustersand 120 stellar associations in the LMC, part of them still embedded inemitting gas. We study age groups in terms of equivalent SWB typesderived from the (U-B) X (B-V) diagram. The size of the spatialdistributions increases steadily with age (SWB types), whereas adifference of axial ratio exists between the groups younger than 30 Myrand those older, which implies a nearly face-on orientation for theformer and a tilt of ~45^deg^ for the latter groups. Asymmetries arepresent in the spatial distributions, which, together with thenoncoincidence of the centroids for different age groups, suggest thatthe LMC disk was severely perturbed in the past.
|The cluster system of the Large Magellanic Cloud|
A new catalog of clusters in the Large Magellanic Cloud has beenconstructed from searches of the IIIa-J component of the ESO/SERCSouthern Sky Atlas. The catalog contains coordinate and diametermeasurements of 1762 clusters in a 25 deg x 25 deg area of sky centeredon the LMC, but excluding the very crowded 3.5 sq deg region around theBar. The distribution of these clusters appears as two superimposedelliptical systems. The higher density inner system extends over about 8deg; the lower density outer system can be represented by a 13 deg x 10deg disk inclined at 42 deg to the line of sight. There are suggestionsof two weak 'arms' in the latter.
|Population-I Pulsating Stars. VI - Ages of Star Clusters and Associations|
On the basis of our age estimations of Population I pulsating stars inour Galaxy (Tsvetkov, 1986a), the mean ages of 6 open star clusterscontaining 21 Delta Scuti-variables and of 8 star clusters andassociations containing 13 classical cepheids, have been evaluated.These mean cluster age estimations weighted according to theprobabilities for different evolutionary phases of the pulsating stars,are obtained in the evolutionary track systems of Iben (1967) andPaczyÃ±ski (1970); the cluster ages are larger in theformer system. Our results are compared with those obtained from variousmethods by other authors. Clusters with classical cepheids and withDelta Scuti-stars have ages, respectively, in the ranges 107_108 yearsand 106_109 years. It is shown that the use of simpleperiod-age(-colour) relations for Population I pulsating stars givessufficiently accurate cluster age estimations. By use of our period-agerelations for classical cepheids (Tsvetkov, 1986a), the mean ages of 56other star clusters and associations in our Galaxy, the MagellanicClouds, and M 31 galaxy have been estimated in both systems of tracks.The results are generally in agreement with those obtained from variousmethods by other authors. The use of Population I pulsating stars instar clusters and associations is one of the simplest and most easilyapplied methods for determining cluster ages; but there are somelimitations in its application
|A Catalogue of Clusters in The LMC|
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