The galaxy as a self-regulated star-forming system - The case of the OB associations

It is proposed that the energy and momentum injected from OB associations can act as the regulators of high-mass star formation throughout the disk of a spiral galaxy. The mechanism, interacting blast waves driven by supernovae and stellar winds, leads to a generalized Schmidt law for the star formation rate and could explain in a natural way the galactic gradients of metals and star formation rate. The formation of massive stars is determined by the average ambient density in the disk while low-mass star formation is regulated by the density in molecular clouds. That is, there are two modes of star formation, but the physical mechanism is the same in both cases.