Speaker
Katharina Fierlinger
(LMU)
Description
Giant molecular clouds (GMCs) are reshuffled by stellar winds and supernova explosions of massive stars. These processes -- which we call stellar feedback -- create bubbles in the interstellar medium and insert newly produced heavy elements and kinetic energy into their surroundings, possibly driving turbulence in GMCs. Most of this energy is thermalized and immediately removed from the GMC by radiative cooling. In this work 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 and the kinetic energy will be dissipated. We argue that the feedback of the most massive star outweighs the feedback from less massive stars.
For a GMC mass of 1e5 Msun (as e.g. found in the Orion GMCs) and a star formation efficiency of 8% the initial mass function (IMF) predicts a most massive star of approximately 60 Msun. For this stellar evolution model we test the dependence of the retained kinetic energy of the cold GMC gas on the inclusion of stellar winds, which insert 2.34 times the energy of a SN and create stellar wind bubbles serving as pressure reservoirs. We find that during the pressure driven phases of the bubble evolution the radiative losses peak near the contact discontinuity (CD) and thus, the retained energy depends on the scales of the mixing processes in the ISM. Without the wind of the progenitor only 0.1% of the SN energy input are retained, whereas taking into account wind-blown bubbles, feedback energy efficiencies of a few percent can be reached.