Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations

Griffith, Emily J.; Weinberg, David H.; Buder, Sven; Johnson, Jennifer A.; Johnson, James W.; Vincenzo, Fiorenzo

Abstract

We investigate the [X/Mg] abundances of 16 elements for 82,910 Galactic disk stars from GALAH+ DR3. We fit the median trends of low-Ia and high-Ia populations with a two-process model, which describes stellar abundances in terms of a prompt core-collapse and delayed Type-Ia supernova component. For each sample star, we fit the amplitudes of these two components and compute the residual Δ[X/H] abundances from this two-parameter fit. We find RMS residuals ≲0.07 dex for well-measured elements and correlated residuals among some elements (such as Ba, Y, and Zn) that indicate common enrichment sources. From a detailed investigation of stars with large residuals, we infer that roughly 40% of the large deviations are physical and 60% are caused by problematic data such as unflagged binarity, poor wavelength solutions, and poor telluric subtraction. As one example of a population with distinctive abundance patterns, we identify 15 stars that have 0.3-0.6 dex enhancements of Na but normal abundances of other elements from O to Ni and positive average residuals of Cu, Zn, Y, and Ba. We measure the median elemental residuals of 14 open clusters, finding systematic ∼0.1−0.4 dex enhancements of O, Ca, K, Y, and Ba and ∼0.2 dex depletion of Cu in young clusters. Finally, we present a restricted three-process model where we add an asymptotic giant branch star (AGB) component to better fit Ba and Y. With the addition of the third process, we identify a population of stars, preferentially young, that have much higher AGB enrichment than expected from their SNIa enrichment.

Citation

Griffith, E. J., Weinberg, D. H., Buder, S., Johnson, J. A., Johnson, J. W., & Vincenzo, F. (2022). Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations. The Astrophysical journal, 931(1), Article 23. https://doi.org/10.3847/1538-4357/ac5826

• Journal Article Type: Article
• Acceptance Date: Feb 22, 2022
• Online Publication Date: May 19, 2022
• Publication Date: May 20, 2022
• Deposit Date: Mar 12, 2022
• Publicly Available Date: May 23, 2022
• Journal: The Astrophysical journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 931
• Issue: 1
• Article Number: 23
• DOI: https://doi.org/10.3847/1538-4357/ac5826
• Keywords: Chemical abundances; Galactic abundances; Core-collapse supernovae; Type Ia supernovae; Asymptotic giant branch stars
• Public URL: https://hull-repository.worktribe.com/output/3948905