The directional analysis of star clusters

Abstract

We introduce the Fry Plot and demonstrate its use in quantifying the directionality in star clusters. Taurus and IC2391 are both found to demonstrate a bias in the Probability Density Function (PDF) for neighbours in the same direction for both small and large separations. The Chamaeleon I cluster and Orion B North star-forming region, by contrast, show a symmetrical PDF at small scales, but a directional bias at large scale. Rho Ophiucus, NGC 1333, IC348 and Serpens Main show broadly symmetrical distribution of neighbours. The Pipe Nebula shows strong directional bias at all scales due to the existence of a dominating linear feature. This technique will be useful for quantifying features in observed and simulated objects, and for comparisons with other directional information, such as polarization, velocity and magnetic field maps. © 2008 RAS.