Evolution of Radial Abundances Gradients from Planetary Nebulae

Extract

The presence of radial abundance gradients is now well established, both in our Galaxy and in other spirals. These gradients were originally derived from oxygen abundance in HII regions, but in the past few years, other elements produced by massive stars have also been shown to display radial abundance gradients similar to the oxygen gradient, which amounts to −0.07 dex kpc⁻¹. Moreover, planetary nebulae (PN), belonging to the intermediate disk population (the so–called Peimbert “type II” PN) also exhibit gradients of the same order of magnitude as the HII regions.