Sedov Taylor

Supernova blast wave in a turbulent ISM

Supenova explosion at the centre of the 3D domain expands into the interstellar medium, to eventually leave a void some 100 parsecs across afre 300 Myr.

Supernova snowplough resolution test

Simulation of a single SN remnant in a uniform ambient ISM at rest for comparison with the snowplough solution and the enhanced result by Cioffi et al 1988. The red movie depicts temperature and blue gas density. 10⁵¹ ergs of energy, half as thermal energy and the rest as kinetic energy, are initially injected into a sphere with radius about the origin adjusted to enclose 60 solar masses. This heats the ISM inside the remnant to above 10 million Kelvin and shock waves exceeding 500 km s^-1 transport the gas from the core of the remnant into a dense expanding shell.

A series of simulations were performed with an ambient atmosphere of various gas number densities (5, 1, 0.1, 0.01 & 0.001 top to bottom rows below) to compare the evolution of the SN remnant with that of the snowplough model. The grid resolution is 4 parsecs, and SN energy is injected half as thermal, with a Gaussian initial profile, and half as kinetic, with a Gaussian initial velocity profile with scale radius R₀. The minimum initial radius, R₀, is 12 parsecs, but for the more diffuse ISM, R₀ is increased such that the total ambient ISM mass within the remnant is 100 solar masses. Slices of the remnant density and temperature profiles are shown, evolving over time, until the shell expansion rate slows to the local sound speed of the ambient ISM. The growth rate and shell speed are plotted to the right, with analytic fits illustrated for the standard snowplough and refined Cioffi models. Without replacing thermal with kinetic energy, the high density model expands too slowly, while the low density models expand to rigorously. With a remnant size representative of the late Sedov-Taylor stage, some tens of thousand years after the SNe, a significant proportion of the energy would have already been converted into kinetic energy. When applying all energy as thermal, cooling at high density is too efficient sapping the SN energy and too inefficient in the diffuse medium leaving surplus energy.