Extraction of a second power-law tail of the density distribution in simulated clouds

TL;DR

This paper develops a method to detect and analyze a second power-law tail in the density distribution of simulated molecular clouds, revealing insights into cloud evolution and star formation processes.

Contribution

It extends existing techniques to reliably identify multiple power-law tails in density PDFs from high-resolution simulations.

Findings

Second power-law tails are detected in most simulations.

The second tail typically has a slope around -1.

The method accurately extracts double power-law tails from smooth PDFs.

Abstract

The emergence and development of a power-law tail (PLT) at the high-density end of the observed column-density distribution is thought to be indicative for advanced evolution of star-forming molecular clouds. As shown from many numerical simulations, it corresponds to a morphologically analogous evolution of the mass-density distribution (\rhopdf). The latter may display also a second, shallower PLT at the stage of collapse of the first formed protostellar cores. It is difficult to estimate the parameters of a possible second PLT due to resolution constraints. To address the issue, we extend the method for the extraction of single PLTs from arbitrary density distributions suggested by Veltchev et al.(2019) to detect a second PLT. The technique is elaborated through tests on an analytic \rhopdf{} and applied to a set of hydrodynamical high-resolution simulations of isothermal self-gravitating clouds. In all but one case two PLTs were detected -- the first slope is always steeper and the second one is typically $\partial \ln V /\ln \rho \sim -1$. These results are in a good agreement with numerical and theoretical works and do suggest that the technique extracts correctly double PLTs from smooth PDFs.