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We present a new grid of ionizing fluxes for O and Wolf-Rayet stars for use with evolutionary synthesis codes and single star Hii region analyses. A total of 230 expanding, non-LTE, line-blanketed model atmospheres have been calculated for five metallicities (0.05, 0.2, 0.4, 1 and 2Z⊙) using the WM-basic code of Pauldrach et al. (2001) for O stars and the cmfgen code of Hillier Miller (1998) for W-R stars. The stellar wind parameters are scaled with metallicity for both O and W-R stars. We compare the ionizing fluxes of the new models with the CoStar models of Schaerer de Koter (1997) and the pure helium W-R models of Schmutz, Leitherer Gruenwald (1992). We find significant differences, particularly above 54eV, where the emergent flux is determined by the wind density as a function of metallicity. The new models have lower ionizing fluxes in the Hei continuum with important implications for nebular line ratios. We incorporate the new models into the evolutionary synthesis code Starburst99 (Leitherer et al. 1999) and compare the ionizing outputs for an instantaneous burst
Smith et al. (Sat,) studied this question.