Photoionization and heating of a supernova-driven turbulent interstellar medium
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The diffuse ionized gas (DIG) in galaxies traces photoionization feedback from massive stars. Through three-dimensional photoionization simulations, we study the propagation of ionizing photons, photoionization heating and the resulting distribution of ionized and neutral gas within snapshots of magnetohydrodynamic simulations of a supernova-driven turbulent interstellar medium. We also investigate the impact of non-photoionization heating on observed optical emission line ratios. Inclusion of a heating term which scales less steeply with electron density than photoionization is required to produce diagnostic emission line ratios similar to those observed with the Wisconsin H alpha Mapper. Once such heating terms have been included, we are also able to produce temperatures similar to those inferred from observations of the DIG, with temperatures increasing to above 15 000 K at heights |z| ≳ 1 kpc. We find that ionizing photons travel through low-density regions close to the mid-plane of the simulations, while travelling through diffuse low-density regions at large heights. The majority of photons travel small distances (≲ 100 pc); however some travel kiloparsecs and ionize the DIG.
Barnes , J E , Wood , K , Hill , A S & Haffner , L M 2014 , ' Photoionization and heating of a supernova-driven turbulent interstellar medium ' Monthly Notices of the Royal Astronomical Society , vol 440 , no. 4 , pp. 3027-3035 . DOI: 10.1093/mnras/stu521
Monthly Notices of the Royal Astronomical Society
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
JB acknowledges the support of an STFC studentship.