A search for mass segregation of stars and brown dwarfs in ρ Ophiuchi


E-mail: rparker@phys.ethz.ch


We apply two different algorithms to search for mass segregation to a recent observational census of the ρ Ophiuchi star-forming region. First, we apply the ΛMSR method, which compares the minimum spanning tree (MST) of a chosen subset of stars to MSTs of random subsets of stars in the cluster, and determine the mass segregation ratio, ΛMSR. Secondly, we apply the m–Σ method, which calculates the local stellar surface density around each star and determines the statistical significance of the average surface density for a chosen mass bin compared to the average surface density in the whole cluster. Using both methods, we find no indication of mass segregation (normal or inverse) in the spatial distribution of stars and brown dwarfs in ρ Ophiuchi. Although ρ Ophiuchi suffers from high visual extinction, we show that a significant mass segregation signature would be detectable, albeit slightly diluted, despite dust obscuration of centrally located massive stars.