Large-scale star formation in the Magellanic Clouds derived from analysis of stellar populations

Sternwarte der Universität Bonn, Auf dem Hügel 71, D -53121 Bonn Ph.D. degree awarded on 13. November 2001 Supershells with diameters larger than 300 pc need gigantic energy amounts of > 1053 erg for their formation. Since they are visible in all irregular galaxies as contiguous shells in H I and Hα, the question about their creation mechanism arises. Photometric studies in UBV passbands in both Magellanic Clouds are presented. They comprise an investigation on five regions (N70, a strip inside and an outer field of LMC2, N171, and N214) at the east side, i.e. at the leading front of the LMC moving through the galactic halo, and data inside the supergiant shells LMC4, LMC1, LMC7, and SMC1. One main result of these studies is the absence of an age gradient on large scales. In LMC4 and LMC1, the young central associations (LH77 and LH15, respectively) consist of coeval stars, thus requiring a large-scale star formation trigger. The photometric results (except of the LMC1 data) derived in 44 CCD fields, which are available electronically✯ , sum up to 314505 BV data points. Of these, 136155 have U information (derived in 14 CCD fields) in addition to BV .