Origin and evolution of moving groups I. Characterization in the observational kinematic-age-metallicity space

TL;DR

This study characterizes moving groups in the Milky Way using kinematic, age, and metallicity data, revealing their complex structures and dependencies, and highlights the need for models incorporating stellar ages and metallicities for better understanding.

Contribution

It provides a detailed observational analysis of moving groups in the U-V-age-[Fe/H] space, emphasizing their properties and the limitations of current formation models.

Findings

Dominant structures are Sirius, Coma Berenices, Hyades-Pleiades, and Hercules.

Kinematic structures depend on Galactic position with varying contrast.

Large age spread observed within all branches.

Abstract

Context. Recent studies have suggested that moving groups have a dynamic or "resonant" origin. Under this hypothesis, these kinematic structures become a powerful tool for studying the large-scale structure and dynamics of the Milky Way. Aims. We aim to characterize these structures in the U-V-age-[Fe/H] space and establish observational constraints that will allow us to study their origin and evolution. Methods. We apply multiscale techniques -wavelet denoising (WD)- to an extensive compendium of more than 24000 stars in the solar neighbourhood with the best available astrometric, photometric and spectroscopic data. Results. We confirm that the dominant structures in the U-V plane are the branches of Sirius, Coma Berenices, Hyades-Pleiades and Hercules, which are nearly equidistant in this kinematic plane and show a negative slope. The abrupt drops in the velocity distribution are characterized. We find a certain dependence of these kinematic structures on Galactic position with a significant change of contrast among substructures inside the branches. A large spread of ages is observed for all branches. The Hercules branch is detected in all subsamples with ages older than ~ 2 Gyr and the set of the other three branches is well established for stars > 400 Myr. The age-metallicity relation of each branch is examined and the relation between kinematics and metallicity is studied. Conclusions. Not all of these observational constraints are successfully explained by the recent models proposed for the formation of such kinematic structures. Simulations incorporating stellar ages and metallicities are essential for future studies. The comparison of the observed and simulated distributions obtained by WD will provide a physical interpretation of the existence of the branches in terms of local or large-scale dynamics. [Abridged]