The chemical enrichment of the Milky Way disk evaluated using conditional abundances

TL;DR

This study analyzes how chemical element abundances in Milky Way disk stars vary with galactic radius at fixed supernovae contributions, revealing element-specific enrichment patterns and systematic variations that inform models of galactic chemical evolution.

Contribution

It introduces a method to quantify the radial variation of multiple element abundances conditioned on supernovae yields, using large stellar surveys, to better understand the Galaxy's enrichment history.

Findings

Neutron capture and light elements show significant radial gradients.

Most elements have minimal radial gradients, less than 0.01 dex/kpc.

Conditional abundance variations differ between low- and high-$ mf extalpha$ sequences.

Abstract

Chemical abundances of stars in the Milky Way disk are empirical tracers of its enrichment history. However, they capture joint-information that is valuable to disentangle. In this work, we seek to quantify how individual abundances evolve across the present-day radius of the disk, at fixed supernovae contribution ([Fe/H], [Mg/Fe]). We use 18,135 APOGEE DR17 red clump stars and 7,943 GALAH DR3 main sequence stars to compare the abundance distributions conditioned on ([Fe/H], [Mg/Fe]) across $3-13$ kpc and $6.5-9.5$ kpc, respectively. In total we examine 15 elements: C, N, Al, K (light), O, Si, S, Ca, ($\alpha$), Mn, Ni, Cr, Cu, (iron-peak) Ce, Ba (s-process) and Eu (r-process). We find that the conditional neutron capture and light elements most significantly trace variations in the disk's enrichment history, with absolute conditional radial gradients $\leq 0.03$ dex/kpc. The other elements studied have absolute conditional gradients $\lesssim 0.01$ dex/kpc. We uncover structured conditional abundance variations as a function of [Fe/H] for the low-$\alpha$, but not the high-$\alpha$ sequence. The average scatter between the mean conditional abundances at different radii is $\sigma_\text{intrinsic} \approx$ 0.02 dex (with Ce, Eu, Ba $\sigma_\text{intrinsic} >$ 0.05 dex). These results serve as a measure of the magnitude via which different elements trace Galactic radial enrichment history once fiducial supernovae correlations are accounted for. Furthermore, we uncover subtle systematic variations in all moments of the conditional abundance distributions that will presumably constrain chemical evolution models of the Galaxy.