The structure of molecular clouds – II. Column density and mass distributions

摘要: The formation of stars is inextricably linked to the structure their parental molecular clouds. Here we take a number nearby giant clouds (GMCs) and analyse column density mass distributions. This investigation based on four new all-sky median colour excess extinction maps determined from Two Micron All Sky Survey data. span range spatial resolution factor 8. allows us determine cloud properties at common scale 0.1 pc, as well study dependence properties. We find that low turbulence-dominated part can be fitted by lognormal distribution. However, above universal threshold 6.0 ± 1.5 mag AV there material compared distribution in all investigated represents currently involved star formation, thus dominated gravity. Its contribution total ranges over two orders magnitude 0.1 10 per cent. implies our sample various stages evolution GMCs. Furthermore, distributions are extremely similar between if only high-extinction material. On other hand, significant differences low-extinction, regions considered. shows turbulent differ depending environment. no influence predominant mode (clustered or isolated) could found. fraction actively governed gravity, with not significantly altered local feedback processes.