Feedback from multiple supernova explosions inside a wind-blown bubble

Abstract

We study the evolution of multiple supernova (SN) explosions inside a pre-exiting cavity blown by winds from massive progenitor stars. Hydrodynamic simulations in one-dimensional spherical geometry, including radiative cooling and thermal conduction, are carried out to follow first the development of the wind-blown bubble during the main sequence and then the evolution of the SN-driven bubble. We find the size and mass of the SN-driven bubble shell depend on the structure of the pre-existing wind bubble as well as the SN explosion energy E SN (= N SN10 51 ergs). The hot cavity inside the bubble is 2–3 times bigger in volume and hotter than that of a bubble created by SNe exploded in a uniform interstellar medium (ISM). For an association with 10 massive stars in the average ISM, the SN-driven shell has an outer radius of R ss ≈ ( 85 pc ) N SN 0.1 and a mass of M ss ≈ ( 10 4.8 M ⊙ ) N SN 0.3 at 10 6 years after the explosion. By that time most of the explosion energy is lost via radiative cooling, while ≲10% remains as kinetic energy and ∼10% as thermal energy. We also calculate the total integrated spectrum of diffuse radiation emitted by the shock-heated gas of the SN bubble. Total number of H Lymann-limit photons scales roughly as Φ 13.6 ≈ 10 61 N SN and those photons carry away 20–55% of the explosion energy. For the models with 0.1 solar metalicity, the radiative energy loss is smaller and the fraction of non-ionizing photons is larger, compared to those with solar metalicity. We conclude the photoionization/heating by diffuse radiation is the most dominant form of feedback from SN explosions into the surrounding medium.