Some stars fade quietly: Varied Supernova explosion outcomes and their effects on the multi-phase interstellar medium

Abstract

We present results from galaxy evolution simulations with a mutiphase Interstellar medium (ISM), a mass resolution of $4$ M$_{\odot}$ and a spatial resolution of 0.5 pc. These simulations include a stellar feedback model that includes the resolved feedback from individual massive stars and accounts for heating from the far UV-field, non-equilibrium cooling and chemistry and photoionization. In the default setting, individual supernova (SN) remnants are realized as thermal injections of $10^{51}$ erg; this is our reference simulation WLM-fid. Among the remaining seven simulations, there are two runs where we vary this number by fixing the energy at $10^{50}$ erg and $10^{52}$ erg (WLM-1e50 and WLM-1e52, respectively). We carry out three variations with variable SN-energy based on the data of Sukhbold et al. (2016) (WLM-variable, WLM-variable-lin, and WLM-variable-stoch). We run two simulations where only 10 or 60 percent of stars explode as SNe with $10^{51}$ erg, while the remaining stars do not explode (WLM-60prob and WLM-10prob). We find that the variation in the SN-energy, based on the tables of Sukhbold et al. (2016), has only minor effects: the star formation rate changes by roughly a factor of two compared to the fiducial run, and the strength of the galactic outflows in mass and energy only decreases by roughly 30 percent, with typical values of $η_m \sim 0.1$ and $η_e \sim 0.05$ (measured at a height of 3 kpc after the hot wind is fully decoupled from the galactic ISM). In contrast, the increase and decrease in the canonical SN-energy has a clear impact on the phase structure, with loading factors that are at least 10 times lower/higher and a clear change in the phase structure. We conclude that these slight modulations are driven not by the minor change in SN-energy but rather by the stochasticity of whether or not an event occurs when variable SN-energies are applied.