The star formation is a multi-scale and multi-physics process that covers several orders of magnitude in spatial and temporal scales. The complex interplay between coupled physical processes involving turbulence, magnetic fields, and thermochemical processes create an interwoven mixture of gas with very different local properties. Our understanding of the gas distribution relies on the modelisation of observations of chemical tracers, which provide integrated properties and are thus affected by optical-depth effects and line confusion. Therefore understanding the actual gas distribution is far from straightforward.
Using high-resolution numerical magnetohydrodynamics simulations, that include the formation of H2, we compute the abundances of several chemical species to unveil the actual 3D distributions.