^13^CO emission in the MWISP ^12^CO molecular clouds

After linking the ^13^CO structure detection rates of the 18190 ^12^CO molecular clouds to their morphologies, i.e., nonfilaments and filaments, we find that the ^13^CO gas structures are primarily detected in ^12^CO clouds with filamentary morphologies. Moreover, these filaments tend to harbor more than one ^13^CO structure. That demonstrates filaments not only have larger spatial scales, but also have more molecular gas structures traced by ^13^CO lines, i.e., local gas density enhancements.

Our results favor the turbulent compression scenario for filament formation, in which dynamical compression of turbulent flows induces local density enhancements. The nonfilaments tend to be in the low-pressure and quiescent turbulent environments of the diffuse interstellar medium.