Star formation history of the solar neighbourhood as told by Gaia

TL;DR

This paper uses Gaia DR2 data and a Bayesian hierarchical model to reconstruct the star formation history of the solar neighborhood, revealing detailed temporal and chemical evolution patterns over the past 10 billion years.

Contribution

It introduces a novel Bayesian hierarchical approach to derive the star formation history from Gaia data, including chemical enrichment, improving upon previous methods.

Findings

Star formation peaked around 10 Gyr ago with slightly subsolar metallicity.

A minimum in star formation occurred around 8 Gyr ago.

Recent star formation shows increasing metallicity up to Z=0.03.

Abstract

The Gaia DR2 catalog is the best source of stellar astrometric and photometric data available today. The history of the Milky Way galaxy is written in stone in this data set. Parallaxes and photometry tell us where the stars are today, when were they formed, and with what chemical content, i.e. their star formation history (SFH). We develop a Bayesian hierarchical model suited to reconstruct the SFH of a resolved stellar population. We study the stars brighter than $G\,=\,15$ within 100 pc of the Sun in Gaia DR2 and derive a SFH of the solar neighbourhood in agreement with previous determinations and improving upon them because we detect chemical enrichment. Our results show a maximum of star formation activity about 10 Gyr ago, producing large numbers of stars with slightly below solar metallicity (Z=0.014), followed by a decrease in star formation up to a minimum level occurring around 8 Gyr ago. After a quiet period, star formation rises to a maximum at about 5 Gyr ago, forming stars of solar metallicity (Z=0.017). Finally, star formation has been decreasing until the present, forming stars of Z=0.03 at a residual level. We test the effects introduced in the inferred SFH by ignoring the presence of unresolved binary stars in the sample, reducing the apparent limiting magnitude, and modifying the stellar initial mass function.