Abstract Observations of the Milky Way’s low- α disk show that several element abundances correlate with age at fixed metallicity, with unique slopes and small scatters around the age–[X/Fe] relations. In this study, we turn to simulations to explore the age–[X/Fe] relations for the elements C, N, O, Mg, Si, S, and Ca that are traced in a FIRE-2 cosmological zoom-in simulation of a Milky Way–like galaxy, m12i, and understand what physical conditions give rise to the observed age–[X/Fe] trends. We first explore the distributions of mono-age populations in their birth and current locations, [Fe/H], and [X/Fe], and find evidence for inside-out radial growth for stars with ages <7 Gyr. We then examine the age–[X/Fe] relations across m12i’s disk and find that the direction of the trends agrees with observations, apart from C, O, and Ca, with remarkably small intrinsic scatters, σ int (0.01 − 0.04 dex). This σ int measured in the simulations is also metallicity dependent, with σ int ≈ 0.025 dex at [Fe/H] = −0.25 dex versus σ int ≈ 0.015 dex at [Fe/H] = 0 dex, and a similar metallicity dependence is seen in the GALAH survey for the elements in common. Additionally, we find that σ int is higher in the inner galaxy, where stars are older and formed in less chemically homogeneous environments. The age–[X/Fe] relations and the small scatter around them indicate that simulations capture similar chemical enrichment variance as observed in the Milky Way, arising from stars sharing similar element abundances at a given birth place and time.
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Tracing Birth Properties of Stars with Abundance Clustering
To understand the formation and evolution of the Milky Way disk, we must connect its current properties to its past. We explore hydrodynamical cosmological simulations to investigate how the chemical abundances of stars might be linked to their origins. Using hierarchical clustering of abundance measurements in two Milky Way–like simulations with distributed and steady star formation histories, we find that groups of chemically similar stars comprise different groups in birth place (
- Award ID(s):
- 1715582
- NSF-PAR ID:
- 10361559
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 924
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 60
- Size(s):
- ["Article No. 60"]
- Sponsoring Org:
- National Science Foundation
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