3D elemental abundances of stars at formation across the histories of Milky Way-mass galaxies in the FIRE simulations

Abstract

We characterize the 3-D spatial variations of [Fe/H], [Mg/H], and [Mg/Fe] in stars at the time of their formation, across 11 simulated Milky Way (MW)- and M31-mass galaxies in the FIRE-2 simulations, to inform initial conditions for chemical tagging. The overall scatter in [Fe/H] within a galaxy decreased with time until $\approx 7$ Gyr ago, after which it increased to today: this arises from a competition between a reduction of azimuthal scatter and a steepening of the radial gradient in abundance over time. The radial gradient is generally negative, and it steepened over time from an initially flat gradient $\gtrsim 12$ Gyr ago. The strength of the present-day abundance gradient does not correlate with when the disk `settled'; instead, it best correlates with the radial velocity dispersion within the galaxy. The strength of azimuthal variation is nearly independent of radius, and the 360 degree scatter decreased over time, from $\lesssim 0.17$ dex at $t_{\mathrm{lb}}=11.6$ Gyr to $\sim 0.04$ dex at present day. Consequently, stars at $t_{\mathrm{lb}}\gtrsim 8$ Gyr formed in a disk with primarily azimuthal scatter in abundances. All stars formed in a vertically homogeneous disk, $\Delta$[Fe/H] $\le 0.02$ dex within $1$ kpc of the galactic midplane, with the exception of the young stars in the inner $\approx 4$ kpc at $z\sim 0$. These results generally agree with our previous analysis of gas-phase elemental abundances, which reinforces the importance of cosmological disk evolution and azimuthal scatter in the context of stellar chemical tagging. We provide analytic fits to our results for use in chemical-tagging analyses.

22 pages, 16 figures, Accepted for publication in MNRAS

References in corpus (40)

• Array Programming with NumPy
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The GALAH Survey: Scientific Motivation
• A New Calculation of the Ionizing Background Spectrum and the Effects of HeII Reionization
• Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations
• The GALAH+ Survey: Third Data Release
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
• 4MOST: Project overview and information for the First Call for Proposals
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• The evolution of the Galactic metallicity gradient from high-resolution spectroscopy of open clusters
• Age dissection of the Milky Way discs: red giants in the Kepler field
• The Open Cluster Chemical Abundances and Mapping Survey: IV. Abundances for 128 Open Clusters using SDSS/APOGEE DR16
• The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
• The GALAH survey: tracing the Galactic disk with Open Clusters
• Open clusters as key tracers of Galactic chemical evolution. III. Element abundances in Berkeley 20, Berkeley 29, Collinder 261, and Melotte 66
• Keeping it Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk
• The KLEVER Survey: Spatially resolved metallicity maps and gradients in a sample of 1.2 < z < 2.5 lensed galaxies
• Galactic abundance gradients from Cepheids : On the iron abundance gradient around 10-12 kpc
• The physics of gas phase metallicity gradients in galaxies
• Inside Out and Upside-Down: The Roles of Gas Cooling and Dynamical Heating in Shaping the Stellar Age-Velocity Relation
• Ages and masses of million Galactic disk main sequence turn-off and sub-giant stars from the LAMOST Galactic spectroscopic surveys
• The bursty origin of the Milky Way thick disc
• Measuring the mixing scale of the ISM within nearby spiral galaxies
• Metallicity Structure in the Milky Way Disk Revealed by Galactic HII Regions
• Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
• Constraining the PopIII IMF with high-z GRBs
• 3-D gas-phase elemental abundances across the formation histories of Milky Way-mass galaxies in the FIRE simulations: initial conditions for chemical tagging
• Oxygen abundance distribution in Galactic disc
• A Relationship Between Stellar Metallicity Gradients and Galaxy Age in Dwarf Galaxies
• Stellar Abundance Maps of the Milky Way Disk
• Radial Migration from Metallicity Gradient of Open Clusters and Outliers
• Strong chemical tagging with APOGEE: 21 candidate star clusters that have dissolved across the Milky Way disc
• Metallicity Gradients of Thick Disk Dwarf Stars
• Milky Way Analogues in MaNGA: Multi-Parameter Homogeneity and Comparison to the Milky Way
• Migration in the shearing sheet and estimates for young open cluster migration
• The radial metallicity gradient and the history of elemental enrichment in M81 through emission-line probes
• The AMBRE Project: Solar neighbourhood chemodynamical constraints on Galactic disc evolution
• Azimuthal variations of oxygen abundance profiles in star-forming regions of disc galaxies in the EAGLE simulations
• Progenitor-mass-dependent yields amplify intrinsic scatter in dwarf-galaxy elemental abundance ratios