Stellar feedback efficiencies: supernovae versus stellar winds

TL;DR

This paper compares the efficiencies of stellar winds and supernovae in injecting kinetic energy into the interstellar medium, highlighting the significant role of winds in energy retention within giant molecular clouds.

Contribution

It quantifies the impact of stellar winds versus supernovae on feedback energy retention, emphasizing the importance of wind-driven bubbles in cold ISM energy dynamics.

Findings

Stellar winds can contribute over twice the energy of supernovae in feedback.

Including stellar winds increases kinetic energy deposition in cold ISM from 0.1% to several percent.

Radiative losses peak near the contact discontinuity, affecting energy retention.

Abstract

Stellar winds and supernova (SN) explosions of massive stars ("stellar feedback") create bubbles in the interstellar medium (ISM) and insert newly produced heavy elements and kinetic energy into their surroundings, possibly driving turbulence. Most of this energy is thermalized and immediately removed from the ISM by radiative cooling. The rest is available for driving ISM dynamics. In this work we estimate the amount of feedback energy retained as kinetic energy when the bubble walls have decelerated to the sound speed of the ambient medium. We show that the feedback of the most massive star outweighs the feedback from less massive stars. For a giant molecular cloud (GMC) mass of 1e5 solar masses (as e.g. found in the Orion GMCs) and a star formation efficiency of 8% the initial mass function predicts a most massive star of approximately 60 solar masses. 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. In our model winds 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 radiative losses peak near the contact discontinuity (CD), and thus, the retained energy depends critically on the scales of the mixing processes across the CD. Taking into account the winds of massive stars increases the amount of kinetic energy deposited in the cold ISM from 0.1% to a few percent of the feedback energy.