On The Extraction Of Power-Law Tails Of The Probability Density Functions In Star-Forming Clouds

The probability density function of column density (N-pdf) is an important indicator for understanding of physics and evolution of molecular clouds (MCs) in star-forming regions. Some N-pdfs derived from observational and numerical works could be decomposed to a lognormal part and a power-law tail (PLT) at their high-density ends. Recently, Veltchev et al. 2019 suggested a new approach for PLT extraction, which is not based on additional assumptions about the other parts of the distribution. In this paper we test the reliability of their method and its sensitivity to the chosen region, by use of numerical simulations of evolving giant MCs on galactic scales from the SILCC project. We found that the low-density gas outside the main filaments of the giant MCs does not contribute to the PLT range. The PLT of the N-pdf of molecular gas does not match the theoretical expectations for gravitational contraction - probably due to the complex chemical evolution and dynamics of MCs.