Ionizing feedback from massive stars in massive clusters: fake bubbles and untriggered star formation

We use Smoothed Particle Hydrodynamics to simulate the formation of a massive (10(6) M-circle dot) stellar cluster system formed from the gravitational collapse of a turbulent molecular cloud. We investigate the hierarchical clustering properties of our model system and we study the influence of the photoionizing radiation produced by the system's multiple O-type stars on the evolution of the protocluster. We find that dense gas near the ionizing sources prevents the radiation from eroding the filaments in which most of the star formation occurs and that instead, ionized gas fills pre-existing voids and bubbles originally created by the turbulent velocity field.