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R. Gutermuth (University of Rochester)
I present an analysis of six young stellar clusters observed as part of the Spitzer Young Stellar Cluster Survey, with focus on the distributions and number densities of cluster members and their relation to the morphologies of the natal molecular clouds. Building on commonly used methods, I develop several new ways to characterize the azimuthal distributions and surface density structure of stellar distributions. I apply these methods to ground-based near-IR observations of three clusters, using extinction mapping and Monte Carlo techniques to model and remove systematic effects associated with field star contamination. I demonstrate the power of combining Spitzer Infrared Array Camera (IRAC) data with ground-based near-IR data to identify the young stellar objects with circumstellar disks or envelopes in a cluster, and show the benefits of using this population to trace distributed star formation sites undetected with statistical methods. The results are that several of the clusters in the sample presented have asymmetric stellar distributions which trace filamentary molecular cloud morphology, while the rest have symmetric distributions which tend to occupy local minima in molecular cloud column density maps. The symmetric clusters are much lower density distributions, and they have far fewer Class~I protostars, suggesting that dynamical evolution may explain their current lack of structure. In reference to the current cluster formation paradigm, I argue from these results that clusters pass through an ``Asymmetric Phase'' in their development, where most stars have at least reached the Class~I protostellar phase and are still gravitationally bound by the mass of the natal molecular cloud. These clouds are usually filamentary, a morphology resulting from turbulence-induced shocks required to dissipate kinetic energy and allow gravitational collapse.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.