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The First Stars and Galaxies: Challenges for the Next Decade Participants
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Talk
Title: Possible Lessons from Present-Day Star Formation Author(s): Ralf Klessen Abstract: Stars and star clusters are the fundamental visible building blocks of galaxies at present days as well as in the early universe. Identifying the physical processes that initiate and regulate stellar birth in our Milky Way can therefore contribute significantly to our understanding of star formation at high redshifts. Today, stars form by gravoturbulent fragmentation of interstellar gas clouds. The supersonic turbulence ubiquitously observed in Galactic molecular gas generates strong density fluctuations, with gravity taking over in the densest and most massive regions. Collapse sets in to build up stars and star clusters. Turbulence plays a dual role. On global scales it provides support, while at the same time it can promote local collapse. This determines the statistical characteristics of a stellar population such as the initial mass function or the spatial distribution of stars or the overall efficiency of star formation. I will review the current progress in Galactic star formation theory and compare to our understanding of stellar birth in the early universe, with special emphasis on the distribution of stellar masses and their dependency on metallicity. I will speculate on why the characteristic stellar mass is roughly constant for a wide variety of environmental conditions and why we expect a transition towards higher masses at metallicities below about 10^-5 times solar.
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