The Excitation and Metallicity of Galactic H ii Regions from Infrared Space Observatory SWS Observations of Mid‐Infrared Fine‐Structure Lines

Abstract

We present mid-infrared Infrared Space Observatory Short-Wavelength Spectrometer (ISO-SWS) observations of the fine-structure emissions lines [Ne II] 12.8 μm, [Ne III] 15.6 μm, [Ne III] 36.0 μm, [Ar II] 6.99 μm, [Ar III] 8.99 μm, [S III] 18.7 μm, [S III] 33.5 μm, and [S IV] 10.5 μm and the recombination lines Brα and Brβ in a sample of 112 Galactic H II regions and 37 nearby extra-Galactic H II regions in the LMC, SMC, and M33. We selected our sources from archival ISO-SWS data as those showing prominent [Ne II] 12.8 μm or [Ne III] 15.6 μm emissions. The Galactic sources have a wide range in galactocentric distance (0kpc