How multiple supernovae overlap to form superbubbles

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

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    49 Citations (Scopus)

    Abstract

    We explore the formation of superbubbles through energy deposition by multiple supernovae (SNe) in a uniform medium. We use the total energy conserving, 3D hydrodynamic simulations to study how SNe correlated in space and time create superbubbles. While isolated SNe fizzle out completely by ∼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 ng0, NOB is sufficiently large. While most of the input energy is still lost radiatively, superbubbles can retain up to ∼5-10 per cent of the input energy in the form of kinetic+thermal energy till 10 Myr for interstellar medium density ng0 ≈ 1 cm−3. We find that the mechanical efficiency decreases for higher densities (ηmech ∝ ng02/3). 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 per cent of the injected energy, thereby explaining the observed smaller size and slower expansion of supershells. We also confirm that a sufficiently large (≳ 104) number of SNe are 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.

    Original languageEnglish
    Pages (from-to)1720-1740
    Number of pages21
    JournalMonthly Notices of the Royal Astronomical Society
    Volume465
    Issue number2
    DOIs
    Publication statusPublished - 1 Feb 2017

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