Lyman continuum extinction by dust in HII regions of galaxies

We examine Lyman continuum extinction (LCE) in H II regions by comparing in frared fluxes of 49 H II regions in the Galaxy, M31, M33, and the Large Meg ellanic Cloud with estimated production rates of Lyman continuum photons. A typical fraction of Lyman continuum photons that contribute to hydrogen io nization in the H II regions of three spiral galaxies is less than or simil ar to 50%. The fraction may become smaller as the metallicity (or dust-to-g as ratio) increases. We examine the LCE effect on estimated star formation rates of galaxies. The correction factor for the Galactic dust-to-gas ratio is 2-5.