High-velocity moving groups in the Solar neighborhood in Gaia DR2

TL;DR

This study applies an advanced wavelet analysis to Gaia DR2 data, revealing approximately twenty new high-velocity stellar groups in the solar neighborhood, enhancing understanding of local stellar kinematics.

Contribution

It introduces an improved wavelet technique for 3D velocity distribution analysis, enabling detection of new high-velocity stellar groups in Gaia DR2 data.

Findings

Discovered about twenty new high-velocity stellar groups.

Highlighted the importance of global significance measures in wavelet analysis.

Demonstrated the effectiveness of the method on Gaia DR2 data.

Abstract

We use an improved wavelet analysis technique to reconstruct the $(U,V,W)$ velocity distribution for $\sim 250000$ stars from Gaia DR2, residing in the solar neighborhood of $200$~pc. The 2D wavelet transforms for three bivariate distributions $(U,V)$, $(U,W)$, and $(V,W)$ were investigated. Though most of currently known (low-velocity) stellar moving groups are densely overlapped in these diagrams, our analysis allowed to detect and disentangle about twenty statistically significant 3D groups of stars with high velocities. Most of them appear new. We also discuss the issue of correct noise thresholding in the wavelet transform and highlight the importance of using a global rather than local statistic for that. Using of a local significance measure may lead to an overstated statistical confidence for individual patterns due to the effect of multiple testing.