Theory of star formation in the central kiloparsec

Abstract

Star formation by gravitational instabilities, sequential triggering, and turbulence triggering are briefly reviewed in order to compare the various mechanisms that are observed in main galaxy disks with those in the inner kiloparsec regions. Although very little is known about inner galaxy triggering mechanisms, there appear to be examples that parallel the well-known mechanisms around us. The balance may shift slightly, however, because of the high densities in nuclear regions. The sequential triggering mode, in which one generation of stars triggers another, should be less prominent compared to gravitational instabilities and turbulence triggering when the ambient density is so high that the local dynamical time scale is less than the lifetime of an O-type star. Regardless of this shift in balance, the star formation rate seems to follow the same column density scaling law as in main disks, probably because it is everywhere saturated to the maximum possible value allowed by the fractal structure of the interstellar medium.