Line emission from filaments in molecular clouds

Filamentary structures are often identified in column density maps of molecular clouds, and appear to be important for both lowand high-mass star formation. Theoretically, these structures are expected to form in regions where the supersonic cloud-scale turbulent velocity field converges. While this model of filament formation successfully reproduces several of their properties derived from column densities, it is unclear whether it can also reproduce their kinematic features. We use a combination of hydrodynamical, chemical, and radiative transfer modelling to predict the emission properties of these dynamically forming filaments in the (CO)-C-13, HCN, and N2H+ J = 1-0 rotational lines. The results are largely in agreement with observations; in particular, line widths are typically subsonic to transonic, even for filaments that have formed from highly supersonic inflows. If the observed filaments are formed dynamically, as our results suggest, no equilibrium analysis is possible, and simulations that presuppose the existence of a filament are likely to produce unrealistic results.

Automated summary

Filamentary structures in molecular clouds, which are important for star formation, are expected to form where the supersonic turbulent velocity field converges. While the existing model reproduces some properties of these structures, it is unclear whether it can reproduce their kinematic features. In this study, we use modeling to predict the emission properties of dynamically forming filaments, and the results are largely consistent with observations, suggesting that equilibrium analysis and simulations assuming the existence of filaments may be unrealistic.