Spatial Distribution of Infall Candidates in Molecular Clumps

Abstract

Stars form through the gravitational collapse of dense molecular cores. Studying where this collapse motion is more likely to occur in molecular clumps will help to understand the formation of stars in various parts of molecular clumps and provide more information for studying star formation. We leverage CO data from the Milky Way Imaging Scroll Painting project, along with basic information on 3533 infall candidates identified via CO spectral lines, to search for the molecular clumps associated with these candidates and investigate the spatial distribution of infall candidates within them. By comparing the distributions obtained by scattering points at a series of certain number densities in a 3D sphere with the real distribution of infall candidates in molecular clumps, we observe that the distribution number density of infall candidates within molecular clumps approximately exhibits Gaussian decay with normalized center distance. Specifically, the relationship between the number density n of infall candidates and their normalized center distance r is $n\propto e^{-a{r}^2}$, where a is the decay coefficient. In ${}^{13}$CO clumps, the best-fitting number density function is $n\propto e^{-4.5r^2}$, while in C${}^{18}$O clumps, it is $n\propto e^{-3.2r^2}$. The results indicate that infall is more likely to occur in the center of molecular cloud clumps, and less likely to occur at the edges of the clumps