On the age heterogeneity of the Pleiades, Hyades and Sirius moving groups

TL;DR

This study examines the age distribution of stars in the Pleiades, Hyades, and Sirius moving groups, providing evidence that supports a dynamical origin rather than a common cluster origin.

Contribution

It offers a detailed analysis of the age heterogeneity in these moving groups, challenging the idea they originate solely from cluster evaporation.

Findings

Moving groups contain a mix of stars with different ages.

Most stars in the groups do not match the clusters' isochrones.

Results support a resonant dynamical origin for the groups.

Abstract

We investigate the nature of the classical low-velocity structures in the local velocity field, i.e. the Pleiades, Hyades and Sirius moving groups. After using a wavelet transform to locate them in velocity space, we study their relation with the open clusters kinematically associated with them. By directly comparing the location of moving group stars in parallax space to the isochrones of the embedded clusters, we check whether, within the observational errors on the parallax, all moving group stars could originate from the on-going evaporation of the associated cluster. We conclude that, in each moving group, the fraction of stars making up the velocity-space overdensity superimposed on the background is higher than the fraction of stars compatible with the isochrone of the associated cluster. These observations thus favour a dynamical (resonant) origin for the Pleiades, Hyades and Sirius moving groups.