Mass-loading in Galactic Winds: the Role of Photoevaporation and Wind Ablation

We present a dynamical scenario of instantaneous dense gas entrainment by stellar winds in a wind-dominated HII region. Stellar winds and radiation pressure will become more important in an HII region as the central star or cluster is sufficiently luminous, therefore the region is windswept instead of photoevaporation-dominated. In our model, a cloud is smaller than the region as a whole, hence its mass injection occurs through either ordinary photoevaporation or wind ablation. We predict that the instantaneous wind ablation will cause strong mixing between hot winds and warm gas, and the mass injection rate of the wind-confined photoevaporated flow is higher than that of the ionizing source.