A Reexamination of Observed and Predicted Stellar Ionizing Fluxes in the Large Magellanic Cloud

E.S. Voges, M.S. Oey, R.A.M. Walterbos, & T.M. Wilkinson

We use H-alpha luminosities of HII regions in the Large Magellanic Cloud to test the latest generation of hot star atmosphere models. These newer models predict softer spectral energy distributions, and imply that less ionizing radiation escapes from classical HII regions than found in our previous study. Our analysis is based on a sample of 14 objects that have comprehensive inventories of spectroscopic classifications for the ionizing stars, and we also present a larger sample of 39 objects for which stellar properties are more roughly estimated from broad-band photometry. Although the latter sample offers crude constraints, the results are fully consistent with, and support those from the former sample. We find that the latest stellar atmosphere models predict that only 20 - 30% of HII regions are density-bounded. This is consistent with the shell-like and filamentary morphology seen in those candidates. With these results, the total photon budget may not provide enough Lyman continuum radiation to account for the diffuse, warm ionized medium.