2015MNRAS.451.3340K

We use magnetohydrodynamical simulations of converging flows to investigate the process of molecular cloud formation and evolution out of the magnetized interstellar medium. Here, we study whether the observed subcritical Hi clouds can become supercritical and hence allow the formation of stars within them. To do so, we vary the turbulent Mach number of the flows, as well as the initial magnetic field strength. We show that dense cores are able to build up under all conditions, but that star formation in these cores is either heavily delayed or completely suppressed if the initial field strength is B > 3µG. To probe the effect of magnetic diffusion, we introduce a tilting angle φ between the flows and the uniform background magnetic field, which mimics non-ideal magnetohydrodynamics effects. Even with highly diffusive flows, the formed cores are devoid of star formation, because no magnetically supercritical regions are build up. Hence we conclude, that the problem of how supercritical cloud cores are generated still persists.