Super-Jeans fragmentation in massive star-forming regions revealed by triangulation analysis

Abstract

Understanding the fragmentation of the gas cloud and the formation of massive stars remains one of the most challenging questions of modern astrophysical research. Either the gas fragments in a Jeans-like fashion, after which the fragments grow through accretion, or the fragmentation length is larger than the Jeans length from the start. Despite significant observational efforts, a consensus has not been reached. The key is to infer the initial density distribution upon which gravitational fragmentation occurs. Since cores are the products of the fragmentation process, the distances between adjacent cores serve as a scale indicator. Based on this observation, we propose a Delaunay triangulation-based approach to infer the density structure before the fragmentation and establish the link between density distribution and gas fragmentation length. We find that at low density, the fragmentation is Jeans-like, and at high densities, the core separations are larger than the prediction of the Jeans fragmentation. This super-Jeans fragmentation is a key step toward the formation of massive stars.