Publication Date:
2016-12-30
Description:
We present three-dimensional magneto-hydrodynamical simulations of the self-gravitating interstellar medium (ISM) in a periodic (256 pc) 3 box with a mean number density of 0.5 cm –3 . At a fixed supernova rate we investigate the multi-phase ISM structure, H 2 molecule formation and density–magnetic field scaling for varying initial magnetic field strengths (0, 6 x 10 –3 , 0.3, 3 μG). All magnetic runs saturate at mass-weighted field strengths of ~1–3 μG but the ISM structure is notably different. With increasing initial field strengths (from 6 x 10 –3 to 3 μG) the simulations develop an ISM with a more homogeneous density and temperature structure, with increasing mass (from 5 to 85 per cent) and volume filling fractions (VFFs; from 4 to 85 per cent) of warm (300 〈 T 〈 8000 K) gas, with decreasing VFFs from ~35 to ~12 per cent of hot gas ( T 〉 10 5 K) and with a decreasing H 2 mass fraction (from 70 to 〈 1 per cent). Meanwhile, the mass fraction of gas in which the magnetic pressure dominates over the thermal pressure increases by a factor of 10, from 0.07 for an initial field of 6 x 10 –3 μG to 0.7 for a 3 μG initial field. In all but the simulations with the highest initial field strength self-gravity promotes the formation of dense gas and H 2 , but does not change any other trends. We conclude that magnetic fields have a significant impact on the multi-phase, chemical and thermal structure of the ISM and discuss potential implications and limitations of the model.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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