MORPHOLOGY AND STELLAR CONTENT OF COMPLEXES IN THE LMC

Three LMC stellar aggregates and two LMC stellar complexes located ins ide the constellations Shapley I, IV, IX, and X have been examined in order to study their morphology and properties. Star counts were perfo rmed on excellent quality film copies of direct plates taken with the 1.2m U.K. Schmidt telescope. They have been used for deriving isodensi ty contour mapping of the four studied regions. Low dispersion objecti ve prism plates taken with the same telescope were also used to classi fy the spectra of the stars down to M(V) similar to 0.0mag. Combinatio n of the two sets of data was used to define the boundaries of these r egions, their age, the density and the spatial distribution of their O B stars. It is therefore found that the bright and massive OB type sta rs are the predominant stellar component of the four studied regions. They are embedded in a fainter and less massive stellar component with in the boundaries of a region, revealed by the isopleths, where the li miting detection magnitude is down to M(V) similar to 1.5mag. Thus it appears that the stellar content of the complexes and aggregates is ma de not only by the stars as massive as similar to 40 M., but they also contain lower mass stars, at least similar to 3 M.. The spatial distr ibution of early type stars (down to MV similar to 0.0mag) shows a gra dient which reveals a region coinciding with the one, defined by the i sopleths, where fainter stars are also located. For the near future, w e plan to study whether the gradient of the radial distribution of the early type stars represents the mass distribution of the molecular cl oud from which these stellar structures are formed, or it is due to se quential star formation process and/or expansion because of the high s tellar winds of the very massive stars.