How multiple supernovae overlap to form superbubbles

Naveen Yadav; Dipanjan Mukherjee; Prateek Sharma; Biman B. Nath

doi:10.1093/mnras/stw2522

paper

How multiple supernovae overlap to form superbubbles

arXiv:1603.00815 · doi:10.1093/mnras/stw2522

Abstract

We explore the formation of superbubbles through energy deposition by multiple supernovae (SNe) in a uniform medium. We use total energy conserving, 3-D hydrodynamic simulations to study how SNe correlated in space and time create superbubbles. While isolated SNe fizzle out completely by $\sim 1$ Myr due to radiative losses, for a realistic cluster size it is likely that subsequent SNe go off within the hot/dilute bubble and sustain the shock till the cluster lifetime. For realistic cluster sizes, we find that the bubble remains overpressured only if, for a given $n_{g 0}$ , $N_{OB}$ is sufficiently large. While most of the input energy is still lost radiatively, superbubbles can retain up to $\sim 5 - 10%$ of the input energy in form of kinetic+thermal energy till 10 Myr for ISM density $n_{g 0} \approx 1$ cm $^{- 3}$ . We find that the mechanical efficiency decreases for higher densities ( $η_{mech} \propto n_{g 0}^{- 2/3}$ ). We compare the radii and velocities of simulated supershells with observations and the classical adiabatic model. Our simulations show that the superbubbles retain only $≲ 10%$ of the injected energy, thereby explaining the observed smaller size and slower expansion of supershells. We also confirm that a sufficiently large ( $≳ 1 0^{4}$ ) number of SNe is required to go off in order to create a steady wind with a stable termination shock within the superbubble. We show that the mechanical efficiency increases with increasing resolution, and that explicit diffusion is required to obtain converged results.

20 pages, 2 tables and 21 figures, Accepted and Published in MNRAS, new convergence study presented in comparison to work by Gentry et al. 2016(http://adsabs.harvard.edu/abs/2016arXiv160601242G), Comments are welcome

How multiple supernovae overlap to form superbubbles

Abstract

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