The CGCA (The Leonard E. Parker Center for Gravitation, Cosmology and Astrophysics) seminars are scheduled for Fridays at 1:00 pm in in the Kenwood Interdisciplinary Research Complex (KIRC) Room KEN 2175. A “brown bag lunch” group will assemble in KEN 4118 (fourth floor kitchenette located next to the elevators) at 12:00 NOON.

Turbulent Massive Star Formation in Giant Molecular Clouds
Daniel Murray, University of Wisconsin-Milwaukee

We perform simulations of star formation in self-gravitating turbulently driven gas. We find that star formation is not a self-similar process; two length scales enter, the radius of the rotationally supported disk, and the radius of the sphere of influence of the nascent star, where the enclosed gas mass exceeds the stellar mass. The character of the flow changes at these two scales. We do not see any examples of inside-out collapse. Rather, the accretion of mass starts at large scales where we see large infall velocities about one-third the free-fall velocity out to a parsec hundreds of thousands of years before a star forms. The density evolves to a fixed attractor; mass flows through this structure onto a sporadically gravitationally unstable disk, and from thence onto the star. In the bulk of the molecular cloud, we find that the turbulent velocity goes like r1/2, in agreement with Larson’s size-linewidth relation. But in the vicinity of star forming regions we find that the turbulent velocity decreases much less rapidly with decreasing radius as seen in observations of massive star forming regions. For radii inside the sphere of influence of the star the turbulent velocity increases inward, with r-1/2 i.e., it increases with increasing density, as seen in observations of massive star forming regions. Finally, we find the forming stars acquire mass from much larger radii than a typical hydrostatic core and the star forming efficiency is nonlinear with time, i.e., the stellar mass increases with the square of the time since the star first forms.