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PV: Plenarvorträge

PV VIII

PV VIII: Plenary Talk

Thursday, March 30, 2006, 09:15–10:00, 1002

Dynamical Processes in Star Formation — •Ralf Klessen — Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam

Stars form by gravoturbulent fragmentation of interstellar gas clouds consisting predominantly of molecular hydrogen as well as small traces of heavier molecules and dust grains. The supersonic turbulence ubiquitously observed in Galactic 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. Or global scales it provides support against gravitational contraction, while at the same time it can promote collapse locally. Stellar birth is thus intimately linked to the dynamical behavior and thermodynamic state of the parental gas cloud, and so depends on its chemical composition and the competition between various heating and cooling mechanisms. Under typical cloud conditions, massive stars form as part of dense clusters following the ‘normal’ mass function observed, e.g. in the solar neighborhood. However, for gas described by an equation of state with effective polytropic index greater than unity star formation becomes biased towards isolated massive stars. This is relevant for understanding the properties of the first stars in the universe or for stars that form under extreme environmental conditions like in the center or our Milky Way.