The State of the Gas Around Young Stellar Groups
  We present the main features in the evolution of the gas pressure in star forming regions, from the formation of the parental cloud to the moment when the region is pressurized by interacting stellar winds. The main processes for cloud destruction and the self-limiting properties of star formation are described. The high star forming efficiency in nuclear starbursts is a consequence of the high gas pressures. The evolution of slow winds in highly pressurized region is also sketched. 
J. Franco (UNAM), T. Plewa (MPA) and G. Garcia-Segura (UNAM)