The erosion and dispersal of massive molecular clouds by young stars

Abstract

The paper evaluates the efficiency with which O stars disperse the molecular clouds from which they form. An O star near the surface of an extended molecular cloud ionizes a H II region which is radiation-bounded on the inner side (towards the cloud center) and density-bounded on the outer side; consequently the ionized gas can stream away into space on the outer side, and this in turn enables the ionization front on the inner side to advance faster into the cloud, thus eroding a large cavity around the O star. This process may be very effective in destroying molecular clouds; if approximately 4 per cent of a cloud's material were converted into new stars with a Salpeter Initial Mass Function, the remaining 96 per cent could be broken up and dispersed by the ionizing radiation from the O stars.