Does feedback help or hinder star formation? The effect of
  photoionisation on star formation in Giant Molecular Clouds
  We investigated the effect of photoionising feedback inside turbulent
star-forming clouds, comparing the resultant star formation in both idealised
profiles and more realistic cloud structures drawn from a global galaxy
simulation. We performed a series of numerical simulations which compared the
effect of star formation alone, photoionisation and photoionisation plus
supernovae feedback. In the idealised cloud, photoionisation suppresses gas
fragmentation at early times, resulting in the formation of more massive stars
and an increase in the star formation efficiency. At later times, the dispersal
of the dense gas causes the radiative feedback effect to switch from positive
to negative as the star formation efficiency drops. In the cloud extracted from
the global simulation, the initial cloud is heavily fragmented prior to the
stellar feedback beginning and is largely structurally unaffected by the late
injection of radiation energy. The result is a suppression of the star
formation. We conclude that the efficiency of feedback is heavily dependent on
the gas structure, with negative feedback dominating when the density is high.
