Universe Colloquium: Stellar feedback in Giant Molecular Clouds: supernovae or stellar winds?

by Katharina Fierlinger (TUM)

Wednesday 22 Jan 2014, 16:30 → 17:30 Europe/Berlin

seminar room, basement (Excellence Cluster Universe)

Giant molecular clouds (GMCs) are reshuffled by feedback of massive stars: Stellar winds and supernova (SN) explosions of massive stars create bubbles in the interstellar medium (ISM) and insert newly produced heavy elements and kinetic energy into their surroundings. However, most of this energy is thermalized and immediately lost via radiative cooling. In the work presented in this talk we estimate the amount of feedback energy that is retained as kinetic energy when the bubble walls have decelerated to the sound speed of the ambient medium. We argue that the feedback of the most massive still existing star outweighs the feedback from less massive stars. Thus, our numerical simulations follow the evolution of a 60 solar mass star, which is the best match between the available stellar models, the assumed cloud mass and the initial mass function (IMF). Another key aspect is the relevance of stellar winds for the retained kinetic energy. In our model the wind inserts 2.34 times the energy of a SN. Additionally bubbles serve as pressure reservoirs and thus enhance the amount of energy retained as kinetic energy of the cold GMC gas. During the pressure driven phases of the bubble evolution the retained energy depends on the scales of the mixing processes in the ISM. Without the wind of the progenitor only 0.1 percent of the SN energy input are retained, whereas taking into account wind-blown bubbles, feedback energy efficiencies of a few percent can be reached. The Universe Colloquium is followed by a social gathering with wine and cheese.