Talk abstract

We identify fourteen well-defined young stellar groups in nearby star-forming regions, having typically 15-40 members with accurate spectral types, complete down to ~0.02 M_solar. Most groups have a stellar mass ratio M_max / M_min > 20, consistent with random sampling of the IMF. The most massive star in a group tends to lie near the group centre, resembling the mass segregation seen in older clusters with more members. In these young groups, such a concentration of massive stars is unlikely to arise dynamically, since the typical member age is at most one or two crossing times. Instead, this mass segregation seems to arise because more massive stars tend to form in central positions of high density.