Fluorescence of [Fe II] in H II regions

Abstract

A study of [Fe II] lines at various positions within the H II regions M42 and M43 is presented. The relative intensities of selected optical [Fe II] lines are shown to be correlated with the intensity of the apparent nebular continuous spectrum. Since the continuum of H II regions is known to be mostly stellar radiation scattered by dust intermixed with the emitting gas, these correlations provide direct evidence for the existence of fluorescent excitation in the formation process of the [Fe II] lines, irrespective of the prevailing physical state.