Playing with positive feedback: external pressure-triggering of a
  star-forming disc galaxy
  Feedback in massive galaxies generally involves quenching of star formation,
a favored candidate being outflows from a central supermassive black hole. At
high redshifts however, explanation of the huge rates of star formation often
found in galaxies containing AGN may require a more vigorous mode of star
formation than attainable by simply enriching the gas content of galaxies in
the usual gravitationally-driven mode that is associated with the nearby
Universe. Using hydrodynamical simulations, we demonstrate that
AGN-pressure-driven star formation potentially provides the positive feedback
that may be required to generate the accelerated star formation rates observed
in the distant Universe.
