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.
|Title of host publication
|HOW DOES THE GALAXY WORK?
|EJ Alfaro, E Perez, J Franco
|Place of Publication
|Number of pages
|Published - 2004
|International Conference on How Does the Galaxy Work - Granada
Duration: 23 Jun 2003 → 27 Jun 2003
|International Conference on How Does the Galaxy Work
|23/06/03 → 27/06/03