Coma Berenices: first evidence for incomplete vertical phase-mixing in local velocity space with RAVE - confirmed with Gaia DR2

TL;DR

This paper provides the first evidence of incomplete vertical phase-mixing in the local velocity space, confirmed with Gaia DR2 data, and links the Coma Berenices moving group to a recent dynamical event involving the Sagittarius dwarf galaxy.

Contribution

It demonstrates the presence of incomplete vertical phase-mixing in the local velocity space and confirms the origin of the Coma Berenices group with Gaia DR2 data.

Findings

Evidence for incomplete vertical phase-mixing in local velocity space.

Confirmation of the Coma Berenices group at negative Galactic latitudes.

Estimated formation time of the group at ~1.5 Gyr ago.

Abstract

Before the publication of the Gaia DR2 we confirmed with RAVE and TGAS an observation recently made with the GALAH survey by Quillen ey al. concerning the Coma Berenices moving group in the Solar neighbourhood, namely that it is only present at negative Galactic latitudes. This allowed us to show that it is coherent in vertical velocity, providing a first evidence for incomplete vertical phase-mixing. We estimated for the first time from dynamical arguments that the moving group must have formed at most ~ 1.5 Gyr ago, and related this to a pericentric passage of the Sagittarius dwarf satellite galaxy. The present note is a rewritten version of the original arXiv post on this result now also including a confirmation of our finding with Gaia DR2.