Signatures of an intermediate-age metal-rich bulge population

TL;DR

This study analyzes elemental abundances and ages of microlensed dwarf stars in the Galactic bulge, revealing an intermediate-age, metal-rich population that challenges the view of the bulge as solely old.

Contribution

It provides detailed elemental and age data for bulge stars, identifying a significant intermediate-age, metal-rich population not previously characterized.

Findings

Metal-poor stars are old with enhanced alpha-elements.

Metal-rich stars show a wide age range, including young stars.

Contradicts the idea that the bulge only contains old stars.

Abstract

We have determined detailed elemental abundances and stellar ages for a sample of now 38 microlensed dwarf and subgiant stars in the Galactic bulge. Stars with sub-solar metallicities are all old and have enhanced alpha-element abundances -- very similar to what is seen for local thick disk stars. The metal-rich stars on the other hand show a wide variety of stellar ages, ranging from 3-4 Gyr to 12 Gyr, and an average around 7-8 Gyr. The existence of young and metal-rich stars are in conflict with recent photometric studies of the bulge which claim that the bulge only contains old stars.