A law for star formation in galaxies
  We study the galactic-scale triggering of star formation. We find that the
largest mass-scale not stabilized by rotation, a well defined quantity in a
rotating system and with clear dynamical meaning, strongly correlates with the
star formation rate in a wide range of galaxies. We find that this relation can
be understood in terms of self-regulation towards marginal Toomre stability and
the amount of turbulence allowed to sustain the system in this self-regulated
quasi-stationary state. We test such an interpretation by computing the
predicted star formation rates for a galactic interstellar medium characterized
by lognormal probability distribution function and find good agreement with the
observed relation.
