AAS 207th Meeting, 8-12 January 2006
Session 196 Star Formation Grab Bag II
Oral, Thursday, 10:00-11:30am, January 12, 2006, Wilson A/B

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[196.05] Star Formation in Space and Time: The Orion Nebula Cluster

E. Huff, S. Stahler (UC Berkeley)

We investigate the star formation history of the Orion Nebula Cluster in both space and time, using the dataset compiled in Hillenbrand (1997). A previous study (Palla & Stahler 1999) found that star formation in the region has accelerated in time, with the bulk of the population forming within the last few million years. We now demonstrate that this acceleration occurred simultaneously, and with equal magnitude, throughout the parent cloud. We find no mass segregation in the traditional sense; the stars produced have the same mass distribution everywhere, with the significant exception of the central Trapezium. In addition, there appears to be no evidence that low-mass stars tended to form more recently. The present-day distribution of stars suggests that the parent cloud, just prior to its dissipation, is well described as a singular isothermal sphere. We use a simple, heuristic model to show that clouds supported by dissipative turbulence undergo accelerating contraction. Accelerating star formation, observed both in the Orion Nebula Cluster and elsewhere, should be a natural consequence of this process.

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