Supernova-driven turbulent metal mixing in high redshift galactic disks: metallicity fluctuations in the interstellar medium and its imprints on metal poor stars in the Milky Way

TL;DR

This study uses numerical simulations to analyze how supernova-driven turbulence mixes metals in galactic disks, impacting the metallicity variations observed in metal-poor stars and providing insights into early star formation conditions.

Contribution

It isolates key processes of turbulent metal mixing at small scales and constrains star formation history and supernova yield variations in the Milky Way through simulations.

Findings

Observed [Mg/Fe] dispersion aligns with early low star-forming conditions.

Metallicity variations in unphase-mixed stars reveal dwarf satellite star formation.

Turbulent diffusion coefficients vary across galaxy environments.

Abstract

The extent to which turbulence mixes gas in the face of recurrent infusions of fresh metals by supernovae (SN) could help provide important constraints on the local star formation conditions. This includes predictions of the metallicity dispersion amongst metal poor stars, which suggests that the interstellar medium was not very well mixed at these early times. The purpose of this {\it Letter} is to help isolate, via a series of numerical experiments, some of the key processes that regulate turbulent mixing of SN elements in galactic disks. We study the gas interactions in small simulated patches of a galaxy disk with the goal of resolving the small-scale mixing effects of metals at pc scales, which enables us to measure the turbulent diffusion coefficient in various galaxy environments. By investigating the statistics of variations of $\alpha$ elements in these simulations, we are able to derive constraints not only on the allowed range of intrinsic yield variations in SN explosions but also on the star formation history of the Milky Way. We argue that the observed dispersion of [Mg/Fe] in metal poor halo stars is compatible with the star-forming conditions expected in dwarf satellites or in an early low star-forming Milky Way progenitor. In particular, metal variations in stars that have not been phase-mixed can be used to infer the star-forming conditions of disrupted dwarf satellites.