Testing stellar yield prescriptions in OMEGA+: Implications for rising sodium abundances in young thick disc stars
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Owusu, Evans K. Ruiter, Ashley J. Kemp, Alex J. Buder, Sven Seitenzahl, Ivo R. Rodriguez-Segovia, Nicolas Pakmor, R. Cinquegrana, Giulia C. Storm, Nicholas Eitner, Philipp Bergemann, Maria |
| author_facet | Owusu, Evans K. Ruiter, Ashley J. Kemp, Alex J. Buder, Sven Seitenzahl, Ivo R. Rodriguez-Segovia, Nicolas Pakmor, R. Cinquegrana, Giulia C. Storm, Nicholas Eitner, Philipp Bergemann, Maria |
| contents | We recently identified an upturn in [Na/Fe] for the population of Solar-type stars in the Galactic young thick disc ($-0.3 < \mathrm{[Fe/H]} < +0.3$) at super-Solar metallicity in data from the GALactic Archaeology with HERMES (GALAH) survey. In this work, we investigate the origin of this unexplained sodium enrichment ([Na/Fe] $\approx 0$--$0.6$~dex) using the OMEGA$+$ galactic chemical evolution code. We explore the rise of [Na/Fe] using four combinations of nucleosynthetic yields from the literature, considering contributions from core-collapse supernovae, asymptotic giant branch stars, and Type~Ia supernovae. Our analysis focuses on two possible drivers of the Na enhancement: a metallicity-dependent increase in Na production from core-collapse supernovae at super-Solar metallicities, and enrichment from metal-rich AGB stars. We adopt two sets of Type~Ia supernova yields, one assuming exclusively Chandrasekhar-mass explosions and the other assuming only sub-Chandrasekhar-mass explosions. We find that the assumed Type~Ia explosion scenario has little influence on the resulting [Na/Fe] evolution, and that all chemical evolution models tested fail to reproduce the observed Na enrichment in the young thick-disc population at super-Solar metallicity. Our results suggest a possible ``under-pollution effect'' by Type~Ia supernovae -- the dominant producers of iron -- in the Solar-type stellar population of the Galactic disc. These findings provide a step toward understanding the origin of the anomalous sodium enrichment at super-Solar metallicities in the Galactic disc. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_17711 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Testing stellar yield prescriptions in OMEGA+: Implications for rising sodium abundances in young thick disc stars Owusu, Evans K. Ruiter, Ashley J. Kemp, Alex J. Buder, Sven Seitenzahl, Ivo R. Rodriguez-Segovia, Nicolas Pakmor, R. Cinquegrana, Giulia C. Storm, Nicholas Eitner, Philipp Bergemann, Maria Astrophysics of Galaxies Solar and Stellar Astrophysics We recently identified an upturn in [Na/Fe] for the population of Solar-type stars in the Galactic young thick disc ($-0.3 < \mathrm{[Fe/H]} < +0.3$) at super-Solar metallicity in data from the GALactic Archaeology with HERMES (GALAH) survey. In this work, we investigate the origin of this unexplained sodium enrichment ([Na/Fe] $\approx 0$--$0.6$~dex) using the OMEGA$+$ galactic chemical evolution code. We explore the rise of [Na/Fe] using four combinations of nucleosynthetic yields from the literature, considering contributions from core-collapse supernovae, asymptotic giant branch stars, and Type~Ia supernovae. Our analysis focuses on two possible drivers of the Na enhancement: a metallicity-dependent increase in Na production from core-collapse supernovae at super-Solar metallicities, and enrichment from metal-rich AGB stars. We adopt two sets of Type~Ia supernova yields, one assuming exclusively Chandrasekhar-mass explosions and the other assuming only sub-Chandrasekhar-mass explosions. We find that the assumed Type~Ia explosion scenario has little influence on the resulting [Na/Fe] evolution, and that all chemical evolution models tested fail to reproduce the observed Na enrichment in the young thick-disc population at super-Solar metallicity. Our results suggest a possible ``under-pollution effect'' by Type~Ia supernovae -- the dominant producers of iron -- in the Solar-type stellar population of the Galactic disc. These findings provide a step toward understanding the origin of the anomalous sodium enrichment at super-Solar metallicities in the Galactic disc. |
| title | Testing stellar yield prescriptions in OMEGA+: Implications for rising sodium abundances in young thick disc stars |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2506.17711 |