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E.K. Grebel (U Wash), W. Brandner (IPAC), Y.-H. Chu (UIUC)
Giant H{\sc ii} regions are extended, very luminous active regions that remain visible even in distant galaxies. They indicate intense, massive large-scale starbursts with possibly present-day globular cluster formation. How does star and cluster formation in giant H{\sc ii} regions proceed? The Milky Way and the Large Magellanic Cloud each contain a spectacular example of a giant H{\sc ii} region: NGC 3603 and 30 Doradus. We have studied large-scale star formation processes in these regions with ground-based and new WFPC2 data. In NGC 3603, we find the 2--3 Myr old central ionizing cluster to be surrounded by older (10--20 Myr) supergiants that have created spectacular elephant-trunk-like structures in the surrounding ISM. To the south of the cluster we find newly formed proplyd-embedded massive stars, more massive and extended than the proplyds in the Eagle Nebula. We compare the large scale picture of NGC 3603 to 30 Doradus, where a very similar multi-stage starburst is going on. In 30 Doradus, the central ionizing cluster R136 with an age of 2--3 Myr is surrounded by 20 Myr old red supergiants and a neighboring 20-Myr old cluster, which may have triggered the collapse of the dense molecular parent cloud of R136, while R136 triggered ongoing star formation found in NICMOS images. We discuss the complex age structure and star formation and trigger processes in greater detail.
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