The return of mass and energy to the interstellar medium by winds from early-type stars

Abstract

The kinetic energy of the stellar winds from a complete sample of B and A supergiants, O stars, and Wolf-Rayet stars has been either measured or estimated from well-defined calibrations. Within a distance of 3 kpc from the sun, these stars are currently returning mass and energy to the interstellar medium (ISM) at an average rate of 9 x 10 to the -5th solar masses/yr/sq Kpc and 2 x 10 to the 38th ergs/s/sq Kpc. Nuclear-processed material in the winds of Wolf-Rayet stars produces enrichment yields for the interstellar gas of 0.0073 for He and 0.0023 for CNO. The input of wind energy from these stars greatly exceeds the wind input from stars of other spectral types, but it is less than the supernovae energy input by about a factor of five. Considering individual phases of the ISM, stellar radiation completely dominates the heating rate of H II regions, supernovae are the major source of energy for the hot intercloud gas and the kinetic energy of the cloud motions, and stellar radiation and supernovae are of equal importance for heating neutral clouds. Although winds are of secondary importance to the global energy equilibrium, they dominate the energetics of the interstellar gas in the vicinity of the more massive OB associations.