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Abundances in Spiral Galaxies: Evidence for Primary Nitrogen Production

L. van Zee·J. J. Salzer·M. P. Haynes
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Abstract

We present the results of nitrogen and oxygen abundance measurements for 185 HII regions spanning a range of radius in 13 spiral galaxies. As expected, the nitrogen-to-oxygen ratio increases linearly with the oxygen abundance for high metallicity HII regions, indicating that nitrogen is predominately a secondary element. However, the nitrogen-to-oxygen ratio plateaus for oxygen abundances less than 1/3 solar (12+log(O/H) < 8.45), as is also seen in low metallicity dwarf galaxies. This result suggests that the observed trend in dwarf galaxies is not due to outflow of enriched material in a shallow gravitational potential. While the effects of infall of pristine material and delayed nitrogen delivery are still unconstrained, nitrogen does appear to have both a primary and secondary component at low metallicities in all types of galaxies.

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L. van Zee, J. J. Salzer, M. P. Haynes. 1998-02-11. Abundances in Spiral Galaxies: Evidence for Primary Nitrogen Production. https://doi.org/10.1086/311263

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