How radiation affects superbubbles: through momentum injection in early phase and photo-heating thereafter

Energetic winds and radiation from massive star clusters push the surrounding gas and blow superbubbles in the interstellarmedium (ISM). Using 1D hydrodynamic simulations, we study the role of radiation in the dynamics of superbubbles driven by a young star cluster of mass 10(6) M-circle dot. We have considered a realistic time evolution of the mechanical power as well as radiation power of the star cluster, and detailed heating and cooling processes. We find that the ratio of the radiation pressure on the shell (shocked ISM) to the thermal pressure (similar to 10(7) K) of the shocked- wind region is almost independent of the ambient density, and it is greater than unity before less than or similar to 1 Myr. We explore the parameter space of density and dust opacity of the ambient medium, and find that the size of the hot gas (similar to 10(7) K) cavity is insensitive to the dust opacity [sigma(d) approximate to (0.1- 1.5) x 10(-21) cm(2)], but the structure of the photoionized (similar to 10(4) K) gas depends on it. Most of the radiative losses occur at similar to 10(4) K, with sub- dominant losses at less than or similar to 10(3) K and similar to 10(6)-10(8) K. The superbubbles can retain as high as similar to 10 per cent of its input energy, for an ambient density of 10(3) m(H) cm(-3). We discuss the role of ionization parameter and recombination- averaged density in understanding the dominant feedback mechanism. Finally, we compare our results with the observations of 30 Doradus.