Abstract
In the Milky Way’s diffuse ionized gas, helium is observed to be underionized relative to hydrogen, implying ionization by a softer radiation field than typical of H ii regions. We construct 3D photoionization models of the diffuse ionized gas and show that the ionizing spectra escaping from leaky H ii regions can provide a solution to the He+/H+ problem. Depending on the spectral type of the ionizing source(s) and the fractional leakage from the H ii region, we find that leaky spectra are harder and have their He-ionizing photon luminosity supressed. Such spectra yield a reduced He+/H+ fraction and increased heating compared to normal stellar spectra.
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Wood, K., Mathis, J.S. (2004). Leaky H II Regions and Heliumionization in the Reynolds Layer. In: Alfaro, E.J., Pérez, E., Franco, J. (eds) How does the Galaxy Work?. Astrophysics and Space Science Library, vol 315. Springer, Dordrecht. https://doi.org/10.1007/1-4020-2620-X_15
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DOI: https://doi.org/10.1007/1-4020-2620-X_15
Publisher Name: Springer, Dordrecht
Print ISBN: 978-1-4020-2619-5
Online ISBN: 978-1-4020-2620-1
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