Publication Date:
2015-03-22
Description:
We use hydrodynamical simulations in a (256 pc) 3 periodic box to model the impact of supernova (SN) explosions on the multiphase interstellar medium (ISM) for initial densities n = 0.5–30 cm –3 and SN rates 1–720 Myr –1 . We include radiative cooling, diffuse heating, and the formation of molecular gas using a chemical network. The SNe explode either at random positions, at density peaks, or both. We further present a model combining thermal energy for resolved and momentum input for unresolved SNe. Random driving at high SN rates results in hot gas ( T 10 6 K) filling 〉90 per cent of the volume. This gas reaches high pressures (10 4 〈 P / k B 〈 10 7 K cm –3 ) due to the combination of SN explosions in the hot, low-density medium and confinement in the periodic box. These pressures move the gas from a two-phase equilibrium to the single-phase, cold branch of the cooling curve. The molecular hydrogen dominates the mass (〉50 per cent), residing in small, dense clumps. Such a model might resemble the dense ISM in high-redshift galaxies. Peak driving results in huge radiative losses, producing a filamentary ISM with virtually no hot gas, and a small molecular hydrogen mass fraction (〈〈1 per cent). Varying the ratio of peak to random SNe yields ISM properties in between the two extremes, with a sharp transition for equal contributions. The velocity dispersion in H i remains 10 km s –1 in all cases. For peak driving, the velocity dispersion in Hα can be as high as 70 km s –1 due to the contribution from young, embedded SN remnants.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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