Planetary Nebula Abundances, Stellar Yields, And The Galactic Evolution of C-12 and N-14

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A project which aims to understand the abundance patterns of He, C, N, O, Ne, S, and Ar for a small sample of planetary nebulae is described. Abundance ratios of O/H, C/O, and N/O especially show a broad range relative to their solar values, and AGB stellar evolution models used to interpret the patterns indicate that reasonable ranges in progenitor mass and metallicity are adequate to explain the observed abundance spread. Chemical yields of intermediate-mass stars inferred from these same models are used to calculate chemical evolution models of the solar neighborhood. These models indicate that intermediate-mass stars account for roughly half of the C-12 and nearly all of the N-14 in that region.