The life-cycle of gas in the multi-phase interstellar medium

Abstract: Molecular clouds (MCs) condense out of the warm interstellar medium (ISM) on scales of several 100 pc and host filamentary substructures on sub-pc scales. They consist of molecular hydrogen (H2 ), which can only be traced indirectly in observations, and are subject to supersonic turbulence. In the SILCC project, we investigate how a multi-phase interstellar medium (ISM) is shaped and stirred by feedback from massive stars. We compare the impact of the explosion sites of Supernovae, and find that a significant fraction needs to explode in low density environments in order to develop an ISM that is in agreement with observations of the Milky Way. Furthermore, we include star cluster formation using sink particles, as well as the massive star feedback from these clusters in the form of ionizing radiation and stellar winds. With these simulations we can show that the early feedback by massive stars limits the accretion of fresh gas, i.e. the growth of the star-forming MCs, and thus regulates the overall star formation efficiency. Further, ionizing radiation changes the phase distribution of the ISM as it destroys H2 in favour of atomic hydrogen.