Measurements of the Far-Infrared [N III] and [O III] Lines in the Outer-Galaxy H II Regions S 206, S 209, and S 212
Session 34 -- Airbourne Astronomy
Display presentation, Tuesday, 9:30-6:30, Pauley Room

## [34.11] Measurements of the Far-Infrared [N III] and [O III] Lines in the Outer-Galaxy H II Regions S 206, S 209, and S 212

H.L. Dinerstein (U.Texas/Austin), M.R. Haas, E.F. Erickson (NASA/ARC), M.W. Werner (JPL)

We report measurements of the far-infrared, fine-structure lines [O III] 52, 88 $\mu$m, and [N III] 57 $\mu$m in three H II regions in the outer Milky Way. The observations were made with a cooled grating spectrometer from NASA's Kuiper Airborne Observatory. This line trio allows one to determine both the gas density and the N/O abundance as traced by the ratio N$^{++}$/O$^{++}$. We measured all three lines from the regions S 206, S 212, and S 209, located at galactocentric distances of 11.5, 14, and 16 kpc, respectively, assuming a solar galactocentric distance of 8.5 kpc. The [O III] electron densities in these H II regions range from log n$_{e}$ = 1.8 to 2.5. For the recently revised collision strength for the [N III] 57 $\mu$m line (Blum and Pradhan 1992, Ap.J.Suppl., 80, 425), the mean value for the ionic N/O ratio in these three regions is N$^{++}$/O$^{++}$ = 0.13 $\pm$ 0.03. Our results for these outer-galaxy regions will be compared with N/O abundances derived from the far-infrared lines for H II regions in the inner part of the Galaxy.

\vskip 5pt This research was supported by NASA Airborne Astronomy grant NAG2-372.