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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.
|The asymptotic giant branch evolution of 1.0-3.0 solar mass stars as a function of mass and composition|
Evolutionary calculations are presented for 1.0-3.0 solar mass stellarmodels covering the abundances Z = 0.001, 0.01, and 0.02 with Y = 0.20and 0.30. Calculations are begun on either the zero-age main sequence orthe zero-age horizontal branch, as appropriate, and includesemiconvection in a simple but effective manner. The existence ofconvective pulses for larger masses is verified. The evolution iscontinued through to the thermally pulsing Asymptotic Giant Branch star.The core masses at the first pulse are found to be larger thanpreviously estimated for masses of no more than two solar masses andsmaller than estimated for masses between 2-3 solar masses. It ispredicted that many stars in this mass range, especially those of lowermetallicity, should begin dredging carbon to their surfaces from thefirst pulse. Some models have had their evolution continued until thethermal pulses reach full amplitude, enabling the derivation of a coremass-luminosity relation for this mass and abundance range. None ofthese models experience the third dredge-up, but this is entirely due tousing alpha = 1.0. Comparison with some individual C stars shows thatthe models presented agree quite well with the observations, providedalpha is about 1.5.
|A Catalogue of Clusters in The LMC|
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