Determination of N/O from far-infrared line observations of Galactic H II regions

Measurements of the 52- and 88-micron forbidden O III line ratios and the 57-micron forbidden N III line ratio for six H II regions have been obtained with the NASA Kuiper Airborne Observatory. The derived N/O ratio for most Galactic regions (of about 0.2-0.3) is greater than that obtained by optical studies, and it exceeds the solar value. Although enhancement of N/O at a galactocentric distance of about 6 kpc may be possible, no evidence is found for an overall linear gradient in N/O with galactocentric distance, suggesting that N-14 is predominantly produced by primary rather than secondary nucleosynthesis.