Simulating the chemistry and dynamics of molecular clouds

We have performed high-resolution three-dimensional simulations of turbulent interstellar gas that for the first time self-consistently follow its coupled thermal, chemical and dynamical evolution. Our simulations have allowed us to quantify the formation timescales for the most important molecules found in giant molecular clouds (H₂, CO), as well as their spatial distribution within the clouds. Our results are consistent with models in which molecular clouds form quickly, within 1-2 turbulent crossing times, and emphasize the crucial role of density inhomogeneities in determining the chemical structure of the clouds.