3D gas-phase elemental abundances across the formation histories of Milky Way-mass galaxies in the FIRE simulations: Initial conditions for chemical tagging

Matthew A. Bellardini, Andrew Wetzel, Sarah R. Loebman, Claude André Faucher-Giguère, Xiangcheng Ma, Robert Feldmann

Research output: Contribution to journalArticlepeer-review

Abstract

We use FIRE-2 simulations to examine 3D variations of gas-phase elemental abundances of [O/H], [Fe/H], and [N/H] in 11 MW and M31-mass galaxies across their formation histories at z ≤ 1.5 (tlookback ≤ 9.4 Gyr), motivated by characterizing the initial conditions of stars for chemical tagging. Gas within 1 kpc of the disc mid-plane is vertically homogeneous to ≲ 0.008 dex at all z ≤ 1.5. We find negative radial gradients (metallicity decreases with galactocentric radius) at all times, which steepen over time from -0.01 dex kpc-1 at z = 1 (tlookback} = 7.8 Gyr) to -0.03 dex kpc-1 at z = 0, and which broadly agree with observations of the MW, M31, and nearby MW/M31-mass galaxies. Azimuthal variations at fixed radius are typically 0.14 dex at z = 1, reducing to 0.05 dex at z = 0. Thus, over time radial gradients become steeper while azimuthal variations become weaker (more homogeneous). As a result, azimuthal variations were larger than radial variations at z ≥ 0.8 (tlookback ≳ 6.9 Gyr). Furthermore, elemental abundances are measurably homogeneous (to ≤0.05 dex) across a radial range of Δ R ≈ 3.5 kpc at z ≥ 1 and Δ R ≈ 1.7 kpc at z = 0. We also measure full distributions of elemental abundances, finding typically negatively skewed normal distributions at z ≥ 1 that evolve to typically Gaussian distributions by z = 0. Our results on gas abundances inform the initial conditions for stars, including the spatial and temporal scales for applying chemical tagging to understand stellar birth in the MW.

Original languageEnglish (US)
Pages (from-to)4586-4607
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Volume505
Issue number3
DOIs
StatePublished - Aug 1 2021

Keywords

  • ISM: Abundances
  • galaxies: Abundances
  • galaxies: Formation
  • galaxies: ISM
  • methods: Numerical
  • stars: Abundances

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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