On the stellar velocity distribution in the solar neighborhood in the light of Gaia DR2

TL;DR

This study models the stellar velocity distribution in the solar neighborhood using Gaia DR2 data, explaining observed structures as effects of spiral arm resonances, and clarifies the origin of moving groups and streams.

Contribution

It introduces a spiral arm resonance model that explains the velocity substructures in the solar neighborhood, aligning with Gaia DR2 observations.

Findings

Main component linked to corotation resonance

Hercules and Sirius streams explained by Lindblad resonances

Model matches Gaia DR2 velocity distribution qualitatively and quantitatively

Abstract

The aim of this work is to contribute to the understanding of the stellar velocity distribution in the solar neighborhood (SN). We propose that the structures on the $U-V$ planes, known as the moving groups, can be mainly explained by the spiral arms perturbations. The applied model of the Galactic disk and spiral arms, with the parameters defined by observational data and with pattern speed $\Omega_p=$28.0 km s$^{-1}$ kpc$^{-1}$, is the same that allowed us to explain the origin of the Local Arm and the Sun's orbit trapped inside the corotation resonance (CR). We show that the $U-V$ picture of the SN consists of the main component, associated with the CR, and the inner and outer structures, which we could associate with the Hercules and Sirius streams, respectively. The Coma-Berenices and Hyades-Pleiades groups and the Sun itself belong to the main part. The substructures of Hercules are formed mainly by the nearby 8/1, 12/1, and even 6/1 inner Lindblad resonances, while Sirius is shaped by the bulk of overlapping outer Lindblad resonances, -8/1, -12/1, -16/1, which are stuck to the CR. This richness in resonances only exists near corotation, which should be of the spiral arms, not of the Galactic bar, whose stable corotation zone is far away from the Sun. The model's predictions of the velocity distribution match qualitatively and quantitatively the distribution provided by Gaia DR2.