Leaky HII regions and helium ionization in the Reynolds layer

K Wood, J S Mathis

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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 it 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 it 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.

Original languageEnglish
Title of host publicationHOW DOES THE GALAXY WORK?
EditorsEJ Alfaro, E Perez, J Franco
Place of PublicationDORDRECHT
Number of pages5
ISBN (Print)1-4020-2619-6
Publication statusPublished - 2004
EventInternational Conference on How Does the Galaxy Work - Granada
Duration: 23 Jun 200327 Jun 2003


ConferenceInternational Conference on How Does the Galaxy Work


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