Galactic anticenter PNe and oxygen abundance

Electron temperatures and densities, as well as chemical abundances for He, N, O, Ne, S, Cl, and Ar were determined. Incorporating these results into our existing database of PN abundances (Henry et al., 2004AJ....127.2284H, Milingo et al., 2010, Cat.

J/ApJ/711/619) yielded a sample of 124 well-observed objects with homogeneously determined abundances extending from 0.9 to 21kpc in galactocentric distance. We performed a detailed regression analysis which accounted for uncertainties in both oxygen abundances and radial distances in order to establish the metallicity gradient across the disk to be 12+log(O/H)=(9.09+/-0.05)-(0.058+/-0.006)xR_g_, with R_g_ in kpc. While we see some evidence that the gradient steepens at large galactocentric distances, more objects toward the anticenter need to be observed in order to confidently establish the true form of the metallicity gradient.