TRIGGERING STAR-FORMATION WITH STELLAR EJECTA

We examine inducing the self-gravitational collapse of molecular cloud cores with stellar ejecta. We study the effect of winds of various st rengths arriving at cloud cores modeled as marginally stable Bonnor-Eb ert spheres, which are unstable both to collapse and to expansion. We find that some winds instigate collapse of the cloud core, while other s result in expansion or destruction of the cloud. Collapse occurs whe n the incident momentum of the ejecta is greater than approximately 0. 1 M. km s(-1) for the standard gamma 1 wind and 1 M. cloud scenario. T he critical momentum, which divides those cases which induce collapse and those which do not, scales as the mass of the cloud times its soun d speed, which is 0.2 M. km s(-1) for the standard 10 K cloud. The cri tical momentum is exceeded for some supernova and many protostellar ou tflows, although if the wind has a velocity greater than approximately 100 km s(-1), the effective adiabatic index will be gamma = 5/3 and t he cloud will be destroyed, through shredding into many pieces. The pl anetary nebulae of AGE stars appear to have momenta below the critical value. However, we found that a high wind temperature (T similar to 6 00 K), possibly characteristic of AGE star winds, could instigate coll apse even in low momentum winds.