Description |
Galactic abundances trace the processing of primordial elements by stars from the birth of the Milky Way to the present day. HII regions, because of their short lifetimes, are ideal targets for abundance determinations because they sample the current state of the interstellar medium. We propose to observe the [OIII], [NIII], and [NII] lines of 31 well-studied Galactic HII regions with the PACS spectrometer to derive the oxygen and nitrogen abundances. We hope to address two long-standing problems in Galactic abundance measurements: 1) abundances traced in the far-infrared show discrepancies with those in the optical, and 2) HII region electron temperatures derived from radio observations, which can be used as a proxy for metallicity, are not well calibrated with abundance measurements. |