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Mason, AC, Crain, RA, Schiavon, RP, Weinberg, DH, Pfeffer, J, Schaye, J, Schaller, M and Theuns, T (2024) Realistic simulated galaxies form [α/Fe]-[Fe/H] knees due to a sustained decline in their star formation rates. Monthly Notices of the Royal Astronomical Society, 533 (1). pp. 184-200. ISSN 0035-8711
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Realistic simulated galaxies form knees due to a sustained decline in their star formation rates.pdf - Published Version Available under License Creative Commons Attribution. Download (5MB) | Preview |
Abstract
We examine the stellar [α/Fe]-[Fe/H] distribution of ≃1000 present-day galaxies in a high-resolution EAGLE simulation. Roughly half of the galaxies exhibit the canonical distribution, characterized by a sequence of low-metallicity stars with high [α/Fe] that transitions at a 'knee' to a sequence of declining [α/Fe] with increasing metallicity. This population yields a knee metallicity-galaxy-mass relation similar to that observed in Local Group galaxies, both in slope and scatter. However, many simulated galaxies lack a knee or exhibit more complicated distributions. Knees are found only in galaxies with star formation histories (SFHs) featuring a sustained decline from an early peak (t ≃ 7 Gyr), which enables enrichment by Type Ia supernovae to dominate that due to Type II supernovae (SN II), reducing [α/Fe] in the interstellar gas. The simulation thus indicates that, contrary to the common interpretation implied by analytic galactic chemical evolution (GCE) models, knee formation is not a consequence of the onset of enrichment by SN Ia. We use the SFH of a simulated galaxy exhibiting a knee as input to the vice GCE model, finding it yields an α-rich plateau enriched only by SN II, but the plateau comprises little stellar mass and the galaxy forms few metal-poor ([Fe/H]≲ 1) stars. This follows from the short constant gas consumption time-scale typically assumed by GCEs, which implies the presence of a readily enriched low-mass gas reservoir. When an initially longer, evolving consumption time-scale is adopted, vice reproduces the simulated galaxy's track through the [α/Fe]-[Fe/H] plane and its metallicity distribution function.
| Item Type: | Article |
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| Uncontrolled Keywords: | methods: analytical; methods: numerical; galaxies: abundances; galaxies: evolution; galaxies: stellar content; astro-ph.GA; astro-ph.GA; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | Oxford University Press |
| SWORD Depositor: | A Symplectic |
| Date Deposited: | 29 Oct 2024 15:00 |
| Last Modified: | 29 Oct 2024 15:00 |
| DOI or ID number: | 10.1093/mnras/stae1743 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/24615 |
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