Gas phase oxygen abundances for HII regions

Regions with enhanced abundances have high ionization parameter, higher H{alpha} luminosity, lower H{alpha} velocity dispersion, younger star clusters, and associated molecular gas clouds showing higher molecular gas densities. This indicates recent star formation has locally enriched the material. Regions with reduced abundances show increased H{alpha} velocity dispersions, suggestive of mixing introducing more pristine material.

We observe subtle azimuthal variations in half of the sample, but cannot always cleanly associate this with the spiral pattern. Regions with enhanced and reduced abundances are found distributed throughout the disk, and in half of our galaxies we can identify subsections of spiral arms with clearly associated metallicity gradients. This suggests spiral arms play a role in organizing and mixing the interstellar medium.