The age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way

TL;DR

This study reveals the complex age and metallicity distribution of stars in the Milky Way bulge, indicating multiple star formation episodes and a diverse stellar population with distinct chemical signatures.

Contribution

It provides detailed insights into the age and abundance structure of the Milky Way bulge using microlensed dwarf and subgiant stars, highlighting multiple star formation events.

Findings

Wide metallicity distribution with multiple peaks.

Significant fraction of young stars at high metallicity.

Multiple star formation episodes at 3, 6, 8, and 11 Gyr ago.

Abstract

The four main findings about the age and abundance structure of the Milky Way bulge based on microlensed dwarf and subgiant stars are: (1) a wide metallicity distribution with distinct peaks at [Fe/H]=-1.09, -0.63, -0.20, +0.12, +0.41; (2) a high fraction of intermediate-age to young stars where at [Fe/H]>0 more than 35 % are younger than 8 Gyr, (3) several episodes of significant star formation in the bulge 3, 6, 8, and 11 Gyr ago; (4) the `knee' in the alpha-element abundance trends of the sub-solar metallicity bulge appears to be located at a slightly higher [Fe/H] (about 0.05 to 0.1 dex) than in the local thick disk.