Measurements of He I \lambda 5876 Recombination Line Radiation from the Diffuse, Warm Ionized Medium in Irregular Galaxies

We report measurements of He I 5876 emission from the ionized gas outside the HII regions in three Magellanic irregular galaxies. The mean reddening-corrected He I / H-alpha intensity ratio is 0.041 independent of spatial location within each galaxy. This value is much higher than that measured in the warm ionized medium of the Milky Way and implies the DIG is ionized by radiation harder than that from a 40,000 K star.