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 interstellar medium (ISM). Using 1-D
hydrodynamic simulations, we study the role of radiation in the dynamics of
superbubbles driven by a young star cluster of mass $10^{6}$ M$_{\odot}$. 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 ($\sim10^{7}$ K) of the shocked wind
region is almost independent of the ambient density, and it is greater than
unity before $\lesssim 1$ Myr. We explore the parameter space of density and
dust opacity of the ambient medium, and find that the size of the hot gas
($\sim$ 10$^{7}$ K) cavity is insensitive to the dust opacity
($\sigma_{d}\approx(0.1-1.5)\times 10^{-21}$ cm$^{2}$), but the structure of
the photoionized ($\sim10^4$ K) gas depends on it. Most of the radiative losses
occur at $\sim10^{4}$ K, with sub-dominant losses at $\lesssim 10^3$ K and
$\sim10^{6}-10^{8}$ K. The superbubbles can retain as high as $\sim 10\%$ of
its input energy, for an ambient density of $10^{3}\,m{\rm_{H}\,cm^{-3}}$. 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.
