An objective determination of blue star groupings in the Andromeda galaxy

We have used an objective method, the Path Linkage Criterion (PLC), to identify large groupings of young stars in the Andromeda Galaxy. Previously, work has been done to objectively identify the structures which correspond in size to the OB associations observed in the Galaxy and Magellanic Clouds (Magnier et al. 1993). In this work, we attempt to identify structures which correspond to the 500 pc-sized complexes described by Efremov et al. (1987) and to test for a hierarchical arrangement of the observed structures. We find that complex-sized structures can naturally be identified using the PLC, and that there is indeed a hierarchical arrangement of the complexes and associations identified.