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Colloquium

Molecular cloud formation and dispersal by stellar feedback

Speaker: Prof Steffi Walch (Cologne)
Date: Wednesday 12 February 2020
Time: 14:00
Venue: Queens Buildings N/3.28

Star formation takes place in the densest and coldest parts of the interstellar medium (ISM), in dark molecular clouds. These are swept up by multiple supernova explosions on scales of several hundred parsec. While condensing out of the warm ISM, the clouds are continuously fed with fresh gas. Thus, the turbulent substructure and magnetic field properties are imprinted during cloud formation. The formation of dense clouds from the multi-phase ISM, the onset of star formation, and the evolution of the molecular clouds under the impact of stellar feedback from newly born massive stars is studied in high-resolution simulations within the SILCC-Zoom project. I will present some of the latest results on the evolution of the clouds. This may happen in relative isolation, as is the case in the solar neighbourhood, but also more turbulent environments are easily arising when considering smaller Galactocentric radii. In the latter case, Supernovae exploding in the vicinity of the clouds, can significantly alter their evolution and drive turbulence. After the onset of star formation, the further evolution of the clouds is heavily influenced by stellar feedback. We find that the detailed cloud substructure determines the clouds' vulnerability to stellar feedback processes, in particular to ionizing radiation. Moreover, the ionization state of the gas can be highly variable on scales of tens of parsec due to small-scale turbulent motions within the star-forming clouds, which shield and release the ionizing radiation. This leads to a flickering of pc-scale HII regions. I will briefly give an overview of how we can use these results to reconcile simulations and observations using molecular lines and dust continuum emission.