PRE-MAIN-SEQUENCE STELLAR POPULATIONS ACROSS SHAPLEY CONSTELLATION III. I. PHOTOMETRIC ANALYSIS AND IDENTIFICATION*, **
We present our investigation of pre‐main-sequence (PMS) stellar populations in the Large Magellanic Cloud (LMC) from imaging with Hubble Space Telescope WFPC2 camera. Our targets of interest are four starforming regions located at the periphery of the super-giant shell LMC 4 (Shapley Constellation III). The PMS stellar content of the regions is revealed through the differential Hess diagrams and the observed colormagnitude diagrams (CMDs). Further statistical analysis of stellar distributions along cross-sections of the faint part of the CMDs allowed the quantitative assessment of the PMS stars census, and the isolation of faint PMS stars as the true low-mass stellar members of the regions. These distributions are found to be well represented by a double Gaussian function, the first component o f which represents the main-sequence field stars and the second the native PMS stars of each region. Based on this result, a cluster membership probability was assigned to each PMS star according to its CMD position. The higher extinction in the region LH 88 did not allow the unambiguous identification of its native stell ar population. The CMD distributions of the PMS stars with the highest membership probability in the regions LH 60, LH 63 and LH 72 exhibit an extraordinary similarity among the regions, suggesting that these stars s hare common characteristics, as well as common recent star formation history. Considering that the region s are located at different areas of the edge of LMC 4, this finding suggests that star formation along the super-gi ant shell may have occurred almost simultaneously. Subject headings:Magellanic Clouds ‐ HII regions ‐ Hertzsprung‐Russell and C‐M diagrams ‐ open clusters and associations: individual (LH 60, LH 63, LH 72, LH 88) ‐ stars: formation ‐ stars: pre‐main-sequence