CfA Colloquium Schedule Fall 2009
 15 October 2009

15 October 2009

Speaker: Alyssa Goodman (Harvard/CfA)

Title:Holistic Star Formation

Abstract:In the end game of star formation, round-ish collections of gas (sometimes known as "dense cores") form individual star/disk systems via gravitational collapse. But: how do those "blobs" arise; how big are they; how round are they; how long do they take to form; how long do they last; and how much do they care about their neighborhood? The answers to these questions determines the nature and rate of star formation in galaxies. Over the past five years, new, large multi-wavelength surveys of star-forming regions and multi-resolution computer simulations have finally allowed us to begin approaching these questions from a statistical, holistic, point of view. The two principal observational surveys allowing for our studies are COMPLETE and Spitzer/c2d, which together have fully mapped out star formation and star-forming material over tens of square degrees of the Perseus, Serpens, and Ophiuchus regions. The "holistic" approach to be discussed in this talk relies upon statistical techniques for inter-comparing results from the observational surveys with synthetic observations of a variety of new numerical simulations (using a process we call "Taste-Testing"). I will focus in part on our recent success in applying a "dendrogram" (tree-diagram) algorithm to cloud structure in order to quantify hierarchical structure, and on dendrograms' potential for identifying the self-gravitating regions of clouds that are true pre-cursors to young stars. I will discuss how good, often three-dimensional, visualization tools are essential both for a "holistic" understanding of the data sets offered by multi-modal surveys like COMPLETE+c2d, and also for understanding the real workings of structure-finding algorithms like dendrograms. One result to be highlighted is the apparent prevalence of spherical shells and/or circular rings within the molecular gas in star-forming regions: the shells, which seem to arise from relatively young, and moderately massive, stars, are much more apparent in "3D" views of molecular line maps than in 2D views, and early analysis indicates that they may be energetic enough to make up for the apparent factor-of-ten deficit in energy needed to drive the observed turbulent motions in star forming regions.

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