Disk Assembly of the Milky Way Suggested from the Time-resolved Chemical Abundance

TL;DR

This study uses recent observational data to support the leaky accretion disk model as a key process in the Milky Way's disk assembly, linking it to universal galaxy formation mechanisms.

Contribution

It provides the first detailed observational validation of the leaky accretion disk scenario for the Milky Way using radial chemical and star formation profiles.

Findings

Radial [Mg/H] profiles match the leaky accretion disk model.

Effective yield estimates align with stellar chemical evolution predictions.

Supports the leaky accretion disk scenario as a universal galaxy formation process.

Abstract

Both simulations and observations suggest that the disk assembly of galaxies is governed by the interplay between coplanar gas inflow, ex-planar gas outflow and in-situ star formation on the disk, known as the leaky accretion disk. This scenario predicts a strong connection between radial distributions of star formation and chemical abundances. The Milky Way, being the sole galaxy where we can reliably measure star formation histories and the corresponding temporally-resolved chemical abundances with individual stars, provides a unique opportunity to scrutinize this scenario. Based on the recent large spectroscopic and photometric surveys of Milky Way stars, we obtain the radial profiles of magnesium abundance ([Mg/H]) and star formation rate (SFR) surface density at different lookback time. We find the radial profiles of [Mg/H] can be well-reproduced using the leaky accretion disk model with only two free parameters for stars formed within 4 Gyr, as well as the flattening at large radii of metallicity profiles traced by HII regions and Cepheids. Furthermore, the constraint effective yield of the Milky Way and nearby galaxies show broad consistency with the theoretical predictions from stellar chemical evolution model with a mass-loading factor of 0-2. These results support that the recent assembly of the Milky Way adheres to the leaky accretion disk scenario, bridging the disk formation of our home galaxy to the big picture of disk formation in the Universe.