Relationship between the column density distribution and evolutionary class of molecular clouds as viewed by ATLASGAL

摘要: We present the first study of relationship between column density distribution molecular clouds within nearby Galactic spiral arms and their evolutionary status as measured from stellar content. analyze a sample 195 located at distances below 5.5 kpc, identified ATLASGAL 870 micron data. define three classes this sample: starless clumps, star-forming with associated young objects, HII regions. find that N(H2) probability functions (N-PDFs) these objects are clearly different: N-PDFs clumps narrowest close to log-normal in shape, while regions exhibit power-law shape over wide range densities log-normal-like components only low densities. use estimate time-scales based on simple analytic model literature. Finally, we show integral N-PDFs, dense gas mass fraction, depends total by ATLASGAL: more massive contain greater relative amounts across all classes.