Clustering properties of stars in simulations of wind-driven star formation

Several recent observational studies have shown that the clustering of young stars in local star-forming regions and of Cepheids in the LMC can be described by a power-law two-point correlation function. We show by numerical simulations that the observed range in power-law slopes can be accounted for by a model in which stellar winds drive expanding shells that are subjected to nonlinear fluid advection and interactions with other shells and in which star formation occurs when a threshold shell column density is exceeded. The models predict how the power-law slope should depend on the maximum age of the stellar sample and the average star formation rate, although a number of effects preclude a comparison with currently available data. We also show how stellar migration flattens the power-law slope below a scale that depends on the velocity dispersion and age of the sample, an effect that may explain the secondary breaks in the observed correlation functions of some regions at large separations. Problems with using the correlation function as a descriptor of clustering structure for statistically inhomogeneous data sets are discussed.