AAS 207th Meeting, 8-12 January 2006
Session 164 Extra-galactic ISM - Near to Far
Oral, Wednesday, 2:00-3:30pm, January 11, 2006, Balcony A

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[164.03] Circumstantial Starbirth in Starbursts: Systematic Variations in the Stellar and Nebular Content of Giant HII Regions in the Local Group Galaxy M33

W. H. Waller (Tufts University), E. J. Murphy (Yale University), R. D. Gehrz, E. Polomski, C. E. Woodward (University of Minnesota), G. G. Fazio (H-S CfA), G. H. Rieke (University of Arizona), Spitzer/M33 Research Team

From the Orion Nebula to the Hubble Deep Field, starburst activity can be seen transforming galaxian clouds of gas into populous clusters of stars. The pyrotechnics and chemical enrichment associated with this activity have led to outcomes as ubiquitous as interstellar dust and as exquisite as life on Earth. In this talk, I will focus on the circumstances of star formation in the environmental context of ongoing starburst activity. I begin with the premises that (1) the formation of a single star takes time, (2) the formation of a populous cluster takes even more time, and (3) ''stuff'' happens in the interim. Hubble images of the Orion Nebula and Eagle Nebula show how hot stars can excavate neighboring clouds of gas and photoevaporate the star-forming cores that are exposed. Hubble observations of giant HII regions in M33 reveal a significant variation in the stellar populations, such that the most metal-rich HII regions contain the greatest proportions of the most massive stars. ISO and Spitzer observations of these same HII regions reveal corresponding variations in the nebular content. These multi-wavelength diagnostics of the stellar-nebular feedback in galaxian starbursts suggest a star-forming mechanism which is subject to photo-evaporative ablation -- an erosive process that is systematically mediated by the metal abundance and corresponding amounts of protective dust in the starbursting environment.

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The author(s) of this abstract have provided an email address for comments about the abstract: william.waller@tufts.edu

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