SF-06-0018

Phase Space Densities of Star-Forming Regions

George Arthur Blaylock-Squibbs

Star formation has been observed to happen in regions with a wide range of morphologies, from highly substructured to smooth and centrally concentrated. Understanding these regions is not only key to understanding the present observed stellar distribution but also the observed exoplanet distribution. Simulations have shown that the initial conditions of star-forming regions (SFRs) can affect planet formation (through photoevaporation and dynamical interactions with the protoplanetary disk) and the orbital parameters of exoplanets. To understand the link between the initial conditions and the evolution of SFRs methods have been developed to quantify the spatio-kinematic substructure of these regions. These methods allow us to compare models and observations. In this poster we present the results of testing a new method from the literature, called the Mahalanobis density (based on the pre-existing Mahalanobis distance), that quantifies the 6D (position and velocity) phase/parameter space density of SFRs. This method has been used to hypothesise that hot Jupiters are more likely to be found around stars in high phase space densities. In this poster we show the initial findings of testing the Mahalanobis density on both static idealised SFRs with a wide range of morphologies and N-body simulations of SFRs with differing initial conditions (such as the degree of substructure, density, presence of exoplanets and virial state). We find that the 3D Mahalanobis distance is unable to differentiate between different morphologies. We find that the 3D Mahalanobis density is more effective at differentiating between different initial virial states than the 6D Mahalanobis density, but only when used in conjunction with established methods (particularly the Q-parameter). This is a somewhat counterintuitive result, as by using more information we are losing diagnostic power. As such we recommend that several methods are used together to infer the initial conditions of SFRs.