Understanding the Kinetic Energy deposition within Molecular Clouds

Abstract

According to the structures traced by ${}^{13}$CO spectral lines within the ${}^{12}$CO molecular clouds (MCs), we investigate the contributions of their internal gas motions and relative motions to the total velocity dispersions of ${}^{12}$CO MCs. Our samples of 2851 ${}^{12}$CO MCs harbor a total of 9556 individual ${}^{13}$CO structures, among which 1848 MCs ($\sim$ 65$\%$) have one individual ${}^{13}$CO structure and the other 1003 MCs ($\sim$ 35$\%$) have multiple ${}^{13}$CO structures. We find that the contribution of the relative motion between ${}^{13}$CO structures ($\ddot{I}{ƒ}_{{}^{13}\mathrm{CO},\mathrm{re}}$) is larger than that from their internal gas motion ($\ddot{I}{ƒ}_{{}^{13}\mathrm{CO},\mathrm{in}}$) in $\sim$ 62$\%$ of 1003 MCs in the `multiple' regime. In addition, we find the $\ddot{I}{ƒ}_{{}^{13}\mathrm{CO},\mathrm{re}}$ tends to increase with the total velocity dispersion($\ddot{I}{ƒ}_{{}^{12}\mathrm{CO},\mathrm{tot}}$) in our samples, especially for the MCs having multiple ${}^{13}$CO structures. This result provides a manifestation of the macro-turbulent within MCs, which gradually becomes the dominant way to store the kinetic energy along with the development of MC scales.

15 pages, 13 figures, accepted for publication in ApJ