From clouds to cores: kinematics in infrared-dark clouds Sarah Ragan MPIA, Heidelberg, Germany
Infrared-dark clouds (IRDCs) contain a range of the earliest phases of cluster formation. Infrared observations have established that IRDCs often host deeply embedded protostars, the local heating from which can be seen in both the dust and gas. But what is the energy budget in IRDCs? Using interferometric maps of high-density molecular tracer, NH$_3$, we examine the kinematic structure and energy content of a sample of IRDCs with differing geometries and varying levels of protostellar activity. We find that corresponding to the warmer regions surrounding protostars there is an accompanying moderate enhancement of the linewidth. The velocity fields are otherwise smooth and well-organized. Overall, the kinetic energy content is drastically insufficient to support the IRDCs against collapse, and the spatial distribution of energy is inconsistent with the turbulent cloud support scenario. We interpret the organized velocity fields as a signature of active global collapse and fragmentation.
Collaborators: Fabian Heitsch, UNC-Chapel Hill, USA Edwin Bergin, University of Michigan, USA David Wilner, SAO, USA	Key publication