The Villafranca project: Combining Gaia and ground-based surveys to study Galactic OB groups

TL;DR

The Villafranca project combines Gaia and ground-based data to study Galactic OB groups, improving astrometric calibration and revealing early dynamical interactions that impact our understanding of massive star evolution and remnants.

Contribution

It provides a new Gaia astrometric calibration and insights into early dynamical interactions affecting the evolution of massive star clusters.

Findings

Improved Gaia astrometric calibration for bright stars.

Early dynamical interactions influence cluster evolution.

Potential underestimation of free-floating neutron stars and black holes.

Abstract

The Villafranca project is studying Galactic stellar groups with OB stars combining information from $Gaia$ and ground-based surveys. We summarize the status of the project and we present its most important results. The Villafranca project has been used to produce a new astrometric calibration for $Gaia$ (E)DR3, which improves the previous one significantly for bright stars. We have discovered that dynamical interactions among massive stars at a very young age ($\sim$1 Ma or less) can play a significant interaction in the dynamical evolution of clusters. As a consequence, our current view of the massive-star IMF may be distorted and the number of free-floating neutron stars and black holes higher than previously considered.