2014/09/08 by R. Ward, Rachel L. Ward, James Wadsley +1 · 1 citation
Chemical Engineering · Mathematics · Physics and Astronomy · #Advanced Combustion Engine Technologies #Astrophysics #Astrophysics and Star Formation Studies #Galaxy #Log-normal distribution #Mathematics #Molecular cloud #Physics #Probability density function #Star formation #Stars #Statistical physics #Statistics #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stu1868
10 pages, 9 figures, Accepted for publication by MNRAS
arxiv created 2014/09/08 · openalex publication_date 2014/10/09 · arxiv updated 2015/06/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The structure of molecular clouds can be characterized with the probability distribution function (PDF) of the mass surface density. In particular, the properties of the distribution can reveal the nature of the turbulence and star formation present inside the molecular cloud. In this paper, we explore how these structural characteristics evolve with time and also how they relate to various cloud properties as measured from a sample of synthetic column density maps of molecular clouds. We find that, as a cloud evolves, the peak of its column density PDF will shift to surface densities below the observational threshold for detection, resulting in an underlying lognormal distribution which has been effectively lost at late times. Our results explain why certain observations of actively star-forming, dynamically older clouds, such as the Orion molecular cloud, do not appear to have any evidence of a lognormal distribution in their column density PDFs. We also study the evolution of the slope and deviation point of the power-law tails for our sample of simulated clouds and show that both properties trend towards constant values, thus linking the column density structure of the molecular cloud to the surface density threshold for star formation.