Ionizing radiation from early-type stars

A grid of NLTE model atmospheres for early-type stars is presented. Model atoms of eleven different elements with various abundances and, for a subset of the models, effects of wind blanketing, are taken into account. These model atmospheres supply realistic emergent fluxes which can be used in ionization calculations for circum- and interstellar gas. The dependence of the ionizing radiation of these stars on spectral type, luminosity class, evolutionary state and stellar environment is discussed.