2-4 micron spectrophotometric observations of compact H II regions

Spectrophotometric observations from 2 to 4 microns of the compact H II regions W51-IRS 2, K3-50, and NGC 7538 are reported. Spectral features observed include hydrogen recombination lines and an absorption attributed to interstellar ice. Extinctions to the various sources are derived based on the observed hydrogen lines and radio fluxes. Thermal dust emission is found to dominate free-free and bound-free emission for wavelengths not less than 2 microns. The ice absorption is analyzed and compared with the extinction and 10 microns silicate absorption. A 3.3 micron emission feature (potentially due to the same material as in NGC 7027) was observed.