Lars Bonne will present his recent PhD thesis 'The formation and dispersal of dense gas in star forming regions" (University of Bordeaux), which received the USRA prize for best SOFIA thesis. He will describe kinematic studies towards both low- and high-mass star forming regions that cover a wide density range, in particular detailing the Musca and DR21 clouds. The dynamics in these regions with different star formation activities show signatures that point to dense filament formation by the same mechanism i.e. the bending of the magnetic field by an oblique shock in a colliding flow which drives continuous mass accretion that forms the dense filament. This fits with indications of shock heating towards several filaments. However, unlike low-mass star forming regions, the higher post-collision density in high-mass star forming regions can initiate gravitational collapse on parsec scale which further facilitates the formation of high-mass stars. When tracing the impact of stellar feedback, in particular with [CII] observations, rapid mass ejection is found, that can counter the gravitationally driven inflow. Stellar feedback might thus play an important role to maintain a low star formation efficiency (SFE) in these collapsing molecular clouds.
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