A comparison of high resolution optical and radio observations of W3.

High resolution maps of the W3 complex for radio continuum and selected optical emission lines are used to derive the visual extinction A(V), the excitation, and the evolutionary state of the component H II regions. A large diffuse H II region in the east, which is the most highly evolved of this type, is found, together with a southern complex of H II regions and a northern complex of young and compact H II regions still embedded in the W3 molecular core. A comparison of the observed dust distribution with ionized and atomic hydrogen and several other molecules in W3 shows the functional relationship between the C-130 column density and A(V) to be in accord with Strohacker's (1978) result for dark clouds.